# Eneloop XX Vs Turnigy 2400 Cycle Testing



## Power Me Up (Oct 24, 2014)

Out of curiosity, I decided to run a cycle life test to compare the high capacity Eneloop XX to the Turnigy 2400. In Australia at least, the Eneloop XX cells are quite expensive - about 30% more than regular Eneloops and they rarely go on special. Regular Eneloops are often on special at less for an 8 pack than the Eneloop XX cells cost for a 4 pack! The Turnigy 2400 cells on the other hand are quite cheap. Ignoring shipping costs, they're cheaper than regular Eneloops even when the Eneloops are on special.

To begin my testing, I took a single Eneloop XX cell and a single Turnigy 2400 cell and placed them both in the same charger. For this test, I decided to run both charging and discharging at only 1 amp - as the cells are only rated for 500 cycles each, I decided that it was worth running the test at a lower rate.







To my surprise, despite being more expensive, the Eneloop XX cell lasted for a significantly lower number of cycles than the Turnigy cell. I then decided to run another test with a pair of Eneloop XX cells to make sure that there wasn't something unusually wrong with the first cell that I tested:






One cell performed very similarly to the first test, but the other lasted for a significantly larger number of cycles. The pattern of capacity decline is pretty much the same, just over a longer number of cycles. It's hard to say what the cause of this difference is - it could be that there is some variation between cells, but I wouldn't expect this considering that normal Eneloops are very consistent, and I would have expected that consistency to carry over into the Eneloop XX line as well.

As a follow up, I decided to run yet another test to compare a Eneloop XX with a Turnigy 2400 cell:






In this latest test, I ran both charges and discharges at 2 amps. In this case, the Eneloop XX survived for more cycles than 2 of the 3 previously tested - despite being run at twice the current. The Turnigy cell managed to last for more cycles, but at no point did it manage to beat the Eneloop XX in capacity.

Overall, I'd say that this is a disappointing result for the Eneloop XX. Unless the absolute maximum capacity is required, I would generally recommend the Turnigy 2400 cells ahead of the Eneloop XX cells - particularly considering the large price difference!


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## Tobias Bossert (Oct 24, 2014)

Do you know what causes the abrupt end of life for NiMH cells? 
I always thought that there will be a continous decline of capacity, not an abrupt end.
What is the behaviour of the cells when they switch to zero capacity: short cirquit or high ohmic?
Were there any temperature problems during testing?


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## lightseeker2009 (Oct 24, 2014)

I have a lot of the Turnigy 2200 cells. I have never compared them with my Eneloops, but they seem to do just as well.


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## LessDark (Oct 24, 2014)

Interesting, any chance you could do this test with regular eneloops as well?


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## Power Me Up (Oct 24, 2014)

LessDark said:


> Interesting, any chance you could do this test with regular eneloops as well?



Like this one?
http://www.ultrasmartcharger.com/phpBB3/viewtopic.php?f=5&t=69


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## Power Me Up (Oct 24, 2014)

Tobias Bossert said:


> Do you know what causes the abrupt end of life for NiMH cells?
> I always thought that there will be a continous decline of capacity, not an abrupt end.
> What is the behaviour of the cells when they switch to zero capacity: short cirquit or high ohmic?
> Were there any temperature problems during testing?



There weren't any temperature problems during this testing - the tests were done a few months ago over winter (in Australia) - it has taken me a while to get around to posting the results.

The cells aren't completely dead when they hit zero on this test. What happens is that as the cells age, their internal resistance increases - it eventually gets to the point where as soon the discharge starts, the voltage drops below the 0.9V cutoff. Prior to that, the voltage drops significantly, but as the cell warms up, the internal resistance drops and the voltage recovers. A normal discharge has the voltage starting high and constantly decreasing. With high current discharges on cells with high internal resistance, the voltage curve ends up looking like an upside down U:


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## RI Chevy (Oct 24, 2014)

Very interesting results. I am surprised at the results.


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## bcwang (Oct 24, 2014)

A couple of ideas here:

- Could the differences you're seeing in the same battery be due to differences in the two slots of your charger? If the voltage sensor is off in one, you could be overcharging in one slot and not the other which would dramatically reduce cycle life.

- Maybe the inflection point termination is not working well on the XX cells and causing an overcharge. 

- The fact that the 2amp charge resulted in better cycle life performance than 2 of the 1amp charge rate cells, points to some evidence the termination might be working better at 2 amps, and/or that charge rate also helps the termination end more reliably with less overcharge.

- Due to eneloop voltage profile during charge being quite different from other nimh cells, the charging mechanism could be overcharging XX and correctly charging your turnigy cells leading to these results.


Those are just some ideas on what might be going on here. Maybe do a log of charge and discharge in the ultrasmartcharger of both slots, trying both types of batteries, including voltage, current, and temp data and we can spot if anything is amiss. The data is pretty random for very consistent cells which points to not a cell problem but a setup problem in my opinion.


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## ChibiM (Oct 25, 2014)

Thanks for the tests!
Very interesting.
its almost as bad as swearing against eneloops  
just kidding. 

I`m quite surprised. Its also very strange to see they just die with even so much juice in them....... I would imagine they would go much worse before totally giving up.. 
It could definitely be the rest time between the cycles?
How many of those charger/discharge setups do you have? 
would be interesting to see, how long they last if they have longer rest time between each cycle. Just like in a real life situation. 

can you post pictures of both the XX cells and Tunirgy cells? Are the XX 1st gen?

At least till now, the Std. eneloop seem to be the better option..


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## apagogeas (Oct 25, 2014)

bcwang said:


> A couple of ideas here:
> ...



I could also add the case the XX eneloops used to be fake.


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## Power Me Up (Oct 26, 2014)

bcwang said:


> A couple of ideas here:
> 
> - Could the differences you're seeing in the same battery be due to differences in the two slots of your charger? If the voltage sensor is off in one, you could be overcharging in one slot and not the other which would dramatically reduce cycle life.



There is a single external 18 bit ADC used for both channels. The ADC has an internal 2.048V reference that is used for all channels. IMHO, a faulty voltage reference would be the most likely cause of incorrect voltage readings, but that would affect all channels the same. There are other possible causes for ADC errors of course, but they shouldn't actually matter too much as long as the error is consistent.

Absolute voltage is critical when charging Lithium Ion cells, but isn't as important when charging NiMH cells because NiMH termination is done based on changes in the voltage rather than the absolute voltage. (let me know if this isn't clear and I need to do a better job of explaining it)

The first 2 tests were done in the same charger. The cell that performed worse was in slot 1 in one test and in slot 2 in the other test, so that pretty much rules out any difference between the channels. I did move the charger to a different location though, so maybe there was some external environmental condition which affected one channel more than the other (i.e. if there was air moving from one side to the other, you would expect that the side on the receiving side would run a bit cooler than the other)



> - Maybe the inflection point termination is not working well on the XX cells and causing an overcharge.



The inflection point ALWAYS occurs before a -dV signal occurs (by definition) If inflection termination causes overcharging, then -dV termination (which always incurs overcharging) is always going to be worse! Having a quick look at the charging data from the first test, I can't see any cases where the cells appear to have been overcharged.

Inflection detection is very reliable - I haven't had a single missed termination in all of the testing/charging that I've done with the UltraSmartCharger - and that includes some cells that were in really bad condition.

This is the first charge for the Eneloop in the first test:





This is the last charge for the Eneloop, again in the first test:





The last charge heats up more at the end, but still terminates OK. I suspect that the increased heat generation is due to lowered charge efficiency caused by damage to the separator increasing the internal resistance. 



> - The fact that the 2amp charge resulted in better cycle life performance than 2 of the 1amp charge rate cells, points to some evidence the termination might be working better at 2 amps, and/or that charge rate also helps the termination end more reliably with less overcharge.



Inflection termination should work reliably at pretty much any current (unlike -dV detection) I haven't done any testing at ultra low charge rates, but I could do that if anyone is interested?

The lower discharge current allows for a more complete discharge. I'm wondering how much damage is actually being done at the end of the discharge as opposed to the end of the charge. I'm thinking about running some tests to see if that if it's possible to work out if deep discharging does more damage than slight overcharging...



> - Due to eneloop voltage profile during charge being quite different from other nimh cells, the charging mechanism could be overcharging XX and correctly charging your turnigy cells leading to these results.



I can't say that I've noticed any significant difference in the voltage profile when charging Eneloops. Do you have any information that you can point to which shows that there is a difference?



> Those are just some ideas on what might be going on here. Maybe do a log of charge and discharge in the ultrasmartcharger of both slots, trying both types of batteries, including voltage, current, and temp data and we can spot if anything is amiss. The data is pretty random for very consistent cells which points to not a cell problem but a setup problem in my opinion.



As I mentioned above, I'd be inclined to think that an external environmental issue might have been a factor - that seems more likely than inconsistent Eneloops...


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## Power Me Up (Oct 26, 2014)

ChibiM said:


> I`m quite surprised. Its also very strange to see they just die with even so much juice in them....... I would imagine they would go much worse before totally giving up..



It seems that increased internal resistance is the cause of these failures and in this case it has happened before much capacity has been lost.

The cells are still usable with good capacity for low current devices.



> It could definitely be the rest time between the cycles?



Shorter rests does mean that the cells don't have as much time to cool down, so yes, I would expect that to have some impact on the results. Checking the data, it's quite clear that the cell temperature haven't had a chance to fully stabilize after each charge/discharge. Ironically, in the short term, the higher cell temperatures will generally mean that the cells will give better performance during the discharge, but in the long term, I wouldn't expect it to be good for their longevity.



> How many of those charger/discharge setups do you have?



I've currently got 3 chargers running testing 24/7. I've got a 4th charger that I'm planning to put into cycle testing service fairly soon.



> would be interesting to see, how long they last if they have longer rest time between each cycle. Just like in a real life situation.



Might be worth running another test to see what the difference is - I agree. It will mean that the test will take longer of course!



> can you post pictures of both the XX cells and Tunirgy cells? Are the XX 1st gen?



Not just at the moment, but I'll try to do it later... I'll have to check which generation they are. Checking the date codes, it looks like 2 of them were made in 2012 and the other 2 were made in 2014...



> At least till now, the Std. eneloop seem to be the better option..



As long as there isn't a pressing need for the increased capacity (and swapping cells isn't an easy option) then, yes - I definitely agree!


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## Power Me Up (Oct 26, 2014)

apagogeas said:


> I could also add the case the XX eneloops used to be fake.



That did cross my mind.

Fakes generally have way less capacity that they're rated for, so I think that makes it unlikely that they're fakes.

I also purchased them from **** Smith Electronics - probably the biggest retailer of Eneloops in Australia. Although fakes can creep in, I wouldn't think that to be too likely since they should be being sourced from the official distribution channels.

I also tested cells from 2 cells each from 2 different packs with different date codes to ensure that I didn't have cells from a faulty batch.


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## Rosoku Chikara (Oct 26, 2014)

Well, a greatly reduced number of useful cycles has always been a drawback of Eneloop Pros (or XX). Despite this fact, I have still chosen to use nothing but Eneloop Pros in all my applications (except for a some early, non-LSD, Panasonic NiMH cells which I am still using until they finally "die off" completely and can be recycled).

Another commonly mentioned drawback is the higher cost of Eneloop Pros. Neither the higher cost, nor the low number of cycles has ever concerned me, however. (In my opinion, the question of whether or not you should be concerned about these two issues depends on how often you intend to recharge your cells, and how many years you hope to keep using them.)

I live in Japan where Turnigy 2400 cells are not a practical option. Turnigy is hardly sold here at all, and almost all "hits" I could find on the internet pertained to "Turnigy" branded multi-cell packs in both Li-Ion and NiMH chemistries for Remote Control hobbyists. 

The only Turnigy AA cell I could find was a 2200 mAh version which were available for purchase at 210 Yen each from one single R/C Hobby Shop. That price is in comparison to 199 Yen for a Standard Eneloop, and 249 Yen for Eneloop Pros. (At the moment, the Yen Dollar exchange rate is fairly close to 100, so you can think in terms of US$2.49 per Eneloop Pro cell.)

While Panasonic literature written in Japanese claims "approximately" 500 cycles (based on the JIS C8708 standard) for the Eneloop Pro cells, it also includes the caveat "depends on your device and device usage -- actual performance may vary." I think it is a well known issue here in Japan that 500 cycles is a rather optimistic claim.

The following is a graph titled "Eneloop Pro Cycle Endurance based on JIS C8708 standard testing methods" that I found on the internet and have partially translated into English:





As you can see, 250 Cycles, or perhaps 300 Cycles (depending on your performance needs) is the most that you can expect. At 350 Cycles the Eneloop Pro has deteriorated very significantly.

The following is a portion of the raw data associated with the above cycle tests:





The JIS C8708 testing involves charging the cell at 0.25C for 3 hours and 10 minutes, then discharging the cell at 0.25C until the cell reaches 1.0 Volts. In order the pass the test, the cell must take longer than 2 hours and 20 minutes to reach 1.0 Volts. Every 50 cycles, the cell is charged at 0.1C for 16 hours, rested for 4 hours, then discharged at 0.20C until it reaches 1.0 Volts.

As the above printout shows, the 376th cycle was the last cycle to "pass" this test. (It took exactly 2 hrs. 20 mins. to reach 1.0V) The cell failed on the 377th cycle because it reached 1.0V in only 2 hrs. 19 mins. The rest of the handwritten notes on this printout refer to the fact that at 400 cycles and 450 cycles, this cell "instantly" registered less than 1.0V (it took "zero time"). 

As I mentioned at the beginning of this post, I (personally) am not particularly troubled by these results. I am willing to accept 200 or 250 cycles as the practical life of my current Eneloop Pros. (That doesn't mean that they cannot still be useful in many low drain applications, even after they have begun to deteriorate significantly.) Since I rarely recharge more than once per week, in my case, 200 or 250 cycles translates into 4 or 5 years. (It is hard for me to predict that far into the future, but I suspect I will be willing to re-invest in whatever the "latest and greatest battery technology" is at that time.)

Without getting into great detail, if you assume 200 or 250 cycles, you will quickly find that the initial higher cost of the Eneloop Pros is trivialized over time. What should not (in my opinion) be trivialized is the nearly 29% increase in capacity. The current Japanese language Panasonic Eneloop website claims "min. 1,900 mAh" for Standard, and "min. 2,450 mAh" for Eneloop Pros. 

Furthermore, the Eneloop Pro has 22% more capacity than the Standard even after 1 whole year, despite its lower 85% capacity retention rate (90% for Standard). To me, these capacity increases are significant. I have recently read where some on this forum have posted that you will see only a very slight increase in capacity, but I wonder how factual that is. 

I do not have any Standards to compare with my Pros, so I cannot say from any firsthand experience, but I do know that Sanyo claimed a 31% runtime increase in an LED flashlight driven at 300 mA. And, to my mind, 31% longer runtime for your flashlight, available every day, whenever you may need it, is pretty significant. (But, I am sure that this depends on your application.)

In summary, I use Eneloops Pros in every device, whether they are needed or not, because that is where I am keeping my "emergency stash" of backup flashlight cells. If my power goes out for any real length of time, I can rob cells from countless "nonessential devices" and use those cells to power more important things like flashlights. I figure that, so long as I make sure and recharge everything (even "nonessential devices") at least once a year, I will always have the "maximum" emergency capacity (always greater than the same number of Standard cells).

Therefore, quite a few of my Eneloop Pros may only get recharged once a year (= 250 to 300 year cell life?) Others will get recharged about once a week (= 4 to 5 years), but only a very few will get recharged much more often than that. I try to keep my cells in matched sets, and occasionally make note of their measured capacity in an Excel spreadsheet that I keep. I am interested to find out for myself when (if ever) I will notice a significant drop-off in capacity.

Some may argue that I shouldn't have spent the money on (made the investment in) Eneloop Pros. But, as previously noted, the cost difference between Standards and Pros is trivial when amortized over time and even "only" 200 cycles. And, in the meantime, I have never purchased another Alkaline cell, I am able to enjoy the highest possible capacity (longest possible runtimes) on a day-to-day basis, and I also have the greatest amount of capacity available for emergency use (should I ever need them). Whats not to like? (Besides initial cost...) 

Think about it, though... How many of us are spending hundreds of dollars on flashlights? Why not invest some of that money into the cells that power those flashlights? Eneloop Pros are not all that expensive when compared to the cost of a quality flashlight. 

(Lets say a good 6 x AA flashlight costs around $100 or so, and the difference between Pros and Standards is $0.50 each. That means 6 Pro cells + 6 spare Pro cells are only going to cost you $6.00 more over Standard Eneloops! You may pay a greater premium for Pros in your market, but I still don't see it as very likely that using Pros is ever going to increase the cost of your flashlight by more than 20%, and even that huge premium seems worth it to me, assuming you are going to experience an appropriate increase in runtime in your application.)

I agree, however, that those who are recharging several times a day, or even once a day, might be better off with Standard... although in my mind even that is still "debatable."


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## StandardBattery (Oct 26, 2014)

Very interesting tests! Thanks!


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## Power Me Up (Oct 26, 2014)

Thanks for the great post Rosoku!

I should have reiterated that my recommendation against the Eneloop XX cells is largely based on their significantly higher cost (at least in Australia)

If I could get Eneloop XX/Pro for only 25% more than the regular Eneloops, I'd do the same as you and standardise on them despite the lower number of cycles that they're capable of. Even for devices that require regular recharging, it might still make sense to use Eneloop XX/Pro cells despite a slight price increase just for improved convenience. Their higher capacity slightly offsets their lower number of cycles as well.

Unfortunately, though, in Australia at least, we have to deal with not just a 25% increase in price but a minimum of 40% more. When the regular Eneloops are on special (which is quire often), the price difference works out to 180% more! Even when the XX/Pro cells are on special they're generally still double the cost of the regular Eneloops on special!

For a handful of cells, the price difference isn't that big a deal, but when you've got over 700 rechargeables in service, the (Australian) price difference makes a huge difference unfortunately!

BTW, I have an Eneloop XX in my EDC torch...


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## Rosoku Chikara (Oct 26, 2014)

Power Me Up said:


> ...For a handful of cells, the price difference isn't that big a deal, but when you've got over 700 rechargeables in service...<snip>



Wow, that really is a whole lot of rechargable cells! 

Sorry to hear that Eneloop Pros are so much more expensive in your market. I noticed that Eneloop Pros (in particular) are being sold on eBay.com.au from Japan, but the prices being charged for them are indeed very high.

In the case of Japan, it seems that the price of Standard Eneloops has gone down. Not too long ago, it was occasionally possible to purchase Pros for less than Standards. (I guess this was because, in general, Pros are not as popular and don't tend to "sell through" quickly enough for some online retailers.) But today, Standards seem to always be cheaper than Pros by a minimum of about 25%.

In any case, I still tend to believe that the difference in cost is overblown, when you take into account that you are likely going to eventually use your cells for at least 200 cycles. Even if you pay twice as much for Pros, that difference amounts to fractions of a cent per cycle... (Of course, Standards probably can achieve well over 1,000 cycles, so their per cycle cost gets ridiculously low, but to me that is beside the point.)

However, as you noted, the difference initial investment cost looms pretty large when you must purchase 700 cells! (I guess you are kept pretty busy recharging all those cells?)


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## Power Me Up (Oct 26, 2014)

Rosoku Chikara said:


> However, as you noted, the difference initial investment cost looms pretty large when you must purchase 700 cells! (I guess you are kept pretty busy recharging all those cells?)



It's not that bad. There are a lot in kids toys that don't get used a lot, so they just get recharged when they go flat. I've also got quite a few unopened in packs (bought at ridiculously low prices) so it's probably a bit over the top on my part to complain about the cost of that many Eneloop XX/Pros when I don't actually need that many in the first place...


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## Mr Floppy (Oct 26, 2014)

Power Me Up said:


> I also purchased them from **** Smith Electronics - probably the biggest retailer of Eneloops in Australia. Although fakes can creep in, I wouldn't think that to be too likely since they should be being sourced from the official distribution channels.



I was thinking you had fakes too but if they are from ****ies then they are genuine. At $27 for four, that is some expense to pay for this experiment.

Now the questions is if Jaycar's XX's are the same or better ... (seriously, don't go out and buy them just for this test)

I guess we don't really buy XX's just for the cycles but the ability to handle high loads but this does put a little perspective on it. Still buying the XX AAA's though


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## Power Me Up (Oct 26, 2014)

Mr Floppy said:


> I was thinking you had fakes too but if they are from ****ies then they are genuine. At $27 for four, that is some expense to pay for this experiment.



Just going from memory, I think I managed to get at least one of the packs for about $20 on special...



> Now the questions is if Jaycar's XX's are the same or better ... (seriously, don't go out and buy them just for this test)



Wasn't planning to. Maybe I should ask Panasonic if they are interested in donating a couple of packs for testing purposes...



> I guess we don't really buy XX's just for the cycles but the ability to handle high loads but this does put a little perspective on it. Still buying the XX AAA's though



Capacity wise, the XX AAA cells are of even less value than the regular Eneloops - 900 mAh min vs 750 mAh min is only a 20% capacity increase compared to 2450/1900 = 29% increase. DSE at least doesn't give a discount on the AAA cells compared to the AA cells even though there are less material costs. (Lower demand for AAA would offset some of these savings of course)

Of course, with the capacity of AAA cells being so low, any increase in capacity could be considered worthwhile in a lot of cases...


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## Mr Floppy (Oct 27, 2014)

Power Me Up said:


> Wasn't planning to. Maybe I should ask Panasonic if they are interested in donating a couple of packs for testing purposes...



Maybe Fujitsu will, I've noticed Fujitsu's 2500mAh range available in Australia now, *HR-3UTHB *model. Lots of the blurb talks about made in japan, original etc.


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## Power Me Up (Oct 27, 2014)

Mr Floppy said:


> Maybe Fujitsu will, I've noticed Fujitsu's 2500mAh range available in Australia now, *HR-3UTHB *model. Lots of the blurb talks about made in japan, original etc.



I strongly suspect that they are the same cell as the Eneloop XX...


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## Rosoku Chikara (Oct 27, 2014)

Power Me Up said:


> I strongly suspect that they are the same cell as the Eneloop XX...



I believe that you are absolutely correct. It is my understanding that they are manufactured in the same plant, and even on the same line at the FDK facility in Takasaki City, Japan. 

When Panasonic acquired the Eneloop brand from Sanyo, FDK acquired the Eneloop manufacturing plant and manufacturing technology from Sanyo. (I know this sounds really odd, but Panasonic could not acquire the actual manufacturing plant due to antitrust issues that would have prevented the Sanyo/Panasonic merger from moving forward.)

Unfortunately, the FDK cells are not low cost. They usually cost more than Eneloops. (However, they are indeed the "original," whereas the new Eneloop cells that are made in China, may or may not be up to the standards set by the original Eneloop. Since Panasonic now owns the Eneloop brand, whatever Panasonic wishes to call an "Eneloop" is a "real" Eneloop. But, we may have to wait and see just how good the new Chinese Eneloop cells are.)


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## WalkIntoTheLight (Oct 27, 2014)

Power Me Up said:


> The cells aren't completely dead when they hit zero on this test. What happens is that as the cells age, their internal resistance increases - it eventually gets to the point where as soon the discharge starts, the voltage drops below the 0.9V cutoff. Prior to that, the voltage drops significantly, but as the cell warms up, the internal resistance drops and the voltage recovers. A normal discharge has the voltage starting high and constantly decreasing. With high current discharges on cells with high internal resistance, the voltage curve ends up looking like an upside down U



Good explanation of why your tests show the capacity suddenly dropping to zero when using 1A discharge. At 0.1A discharge, they may still have plenty of life left.

I notice that they still seem to take a 1A charge okay, even when they can no longer do a 1A discharge. And they only heat up slightly more. Is that expected behaviour? I have some very old (non LSD) NiMH cells, and they can do a slow-discharge fine. However, they must also be charged slowly, or they quickly terminate their charge early. They would quickly overheat if I forced a 1A charge into them.

So it seems odd that the XX Eneloops are able to take a 1A charge, even when internal resistance has wrecked them.


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## Power Me Up (Oct 27, 2014)

WalkIntoTheLight said:


> Good explanation of why your tests show the capacity suddenly dropping to zero when using 1A discharge.



Thanks! 



> At 0.1A discharge, they may still have plenty of life left.



Undoubtedly! Even at a 500 mA discharge, they still had substantial capacity remaining even after they failed a 1 amp discharge.



> I notice that they still seem to take a 1A charge okay, even when they can no longer do a 1A discharge. And they only heat up slightly more. Is that expected behaviour?



Yes, I'm not surprised by that. Higher IR just means that the charging voltage will be substantially higher than for a cell with low IR. Initially, the cells heat up more, but as they warm up, the IR drops and charging becomes more efficient than at the start.



> I have some very old (non LSD) NiMH cells, and they can do a slow-discharge fine. However, they must also be charged slowly, or they quickly terminate their charge early. They would quickly overheat if I forced a 1A charge into them.



It depends on how high the IR is - If it's high enough, then yes, you can't charge them at high rates. I had some old cells that I did some testing on and they had IR values over 1 ohm - they definitely wouldn't charge at 1A, but they couldn't even do a discharge at 0.5 A

With the UltraSmartCharger, I've programmed it to initially reject cells that have an IR over 300 milliohms (so that you can't accidentally recharge alkalines, etc) you can still override this to charge high IR cells - with the default settings, the charge current will be automatically reduced if the IR is over 400 milliohms. As the cells warm up and their IR drops, the charger will automatically increase the charging current to suit.


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## apagogeas (Oct 28, 2014)

Fair comments about genuine or not XX batteries and indeed it looks like a surprise to have another brand exceed XX in cycle life. However, a couple of extra points here: what is the average capacity of Turnigy vs XX? So do we really compare the same thing here? I know XX state minimum 2400 but in practice it is more than 2500, at least those I have here, so if Turnigy is let's say average 2450mAh and XX registers 2530mAh or so, we have almost 100mAh extra which can be a huge difference in actual life. After all, 2530(XX)-1980mAh(standard eneloop)= 550mAh is enough to significantly drop the cycle life from 2100 down to 500 only! If just 550mAh are enough to cause this, it could make sense to expect lower cycle life when we compare a 2530mAh battery vs an 2450 one and in reality, if XX produced the same average to Turnigy the real XX cycle would be superior. I just find hard to believe, an equal capacity battery of another brand performs better to eneloop technology when eneloop is the only battery that claims the highest cycle life on standard eneloops and the same technology is used on XX, so at least part of that performance is expected to also show on XX. So, maybe the difference is due to Turnigy actually producing a lower overall capacity?
Anyway, good to know there is a good alternative nevertheless. It is not impossible for Turnigy to actually have produced a superior battery but if they did, I would expect they'd also produce a 1900mAh minimum capacity battery that surpasses standard eneloops too in total cycle life using that superior technology. I'm not aware of such a battery yet.


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## Power Me Up (Oct 28, 2014)

Yes, the Eneloop XX has more capacity than the Turnigy 2400 - you can see the difference in the graphs in my first post.

You're quite possibly right that the increase in capacity is relevant - getting higher capacity requires compromises in other areas, so it's quite possible that Sanyo had to make more compromises to get that little bit extra capacity.

BTW, for anyone looking for the Turnigy cells, I purchased mine from HobbyKing:
http://hobbyking.com/hobbyking/stor...2400mAh_Low_Self_Discharge_ready_to_use_.html

There is now a Turnigy 2550 mAh cell, so it might be interesting to test it at some stage:
http://hobbyking.com/hobbyking/stor...ow_Self_Discharge_ready_to_use_4pc_pack_.html

Looks like the price on the 2400 mAh cells has dropped significantly at their international warehouse - I'm guessing that they're clearing out stock now that the 2550 mAh cells are available!


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## Power Me Up (Oct 28, 2014)

ChibiM said:


> can you post pictures of both the XX cells and Tunirgy cells? Are the XX 1st gen?



Sorry I didn't get around to taking the photo until now:







Full size version:
http://www.ultrasmartcharger.com/Eneloop XX and Turnigy 2400 Photo.jpg

Looks like the model code on the Eneloops are HR-3UWXB which would make them 2nd gen.

Edit: Date codes on 2 of the Eneloops are: 12-10 HM. The other 2 are: 13-08 EE


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## Power Me Up (Oct 28, 2014)

Rosoku Chikara said:


> The JIS C8708 testing involves charging the cell at 0.25C for 3 hours and 10 minutes, then discharging the cell at 0.25C until the cell reaches 1.0 Volts. In order the pass the test, the cell must take longer than 2 hours and 20 minutes to reach 1.0 Volts. Every 50 cycles, the cell is charged at 0.1C for 16 hours, rested for 4 hours, then discharged at 0.20C until it reaches 1.0 Volts.



Do you have access to the actual JIS C8708 testing standard? If so, can you confirm what rest periods are included in the test. From your text and the image that you posted, it appears that there isn't any rest after charging or discharging, except after the 16 hour 0.1C charge.

I'm thinking about running another test following that standard as closely as I can. The main difference would be that I won't be keeping to standard lab temperature - unless Panasonic or someone else wants to pay for the electricity bill to run my (Panasonic no less) air conditioner 24/7 for the duration of the test. Would take around 3 months or so for the Eneloop XX cells - maybe around a whole year(!) for standard Eneloops!


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## Mr Floppy (Oct 28, 2014)

Power Me Up said:


> I'm thinking about running another test following that standard as closely as I can. The main difference would be that I won't be keeping to standard lab temperature - unless Panasonic or someone else wants to pay for the electricity bill to run my (Panasonic no less) air conditioner 24/7 for the duration of the test. Would take around 3 months or so for the Eneloop XX cells - maybe around a whole year(!) for standard Eneloops!



What temperature would that have be? I have full access to a rack in our computer room, the room is set to be 18 degrees C but normally it is around 26 in the racks.


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## Power Me Up (Oct 28, 2014)

Mr Floppy said:


> What temperature would that have be? I have full access to a rack in our computer room, the room is set to be 18 degrees C but normally it is around 26 in the racks.



Standard laboratory temperature is supposed to be 25 degrees C. I'm not sure what temperature the JIS standard requires though...


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## Rosoku Chikara (Oct 28, 2014)

Power Me Up said:


> Do you have access to the actual JIS C8708 testing standard? If so, can you confirm what rest periods are included in the test. From your text and the image that you posted, it appears that there isn't any rest after charging or discharging, except after the 16 hour 0.1C charge...



Well, the short answer is "No." But, I am not so good with "short answers," so please allow me to explain. 

I did find a copy of JIS C8708 : 2007 (may nor may not be the current version) posted on the internet. Without paying the money to purchase a "legit" copy, it is hard to know if the copy I found is "real." But, it looks real enough to me. It is not in the best of shape (meaning, my browser does a poor job of rendering the subscript and superscript of its formulas... and in addition, I highly suspect that it is an OCR-->HTML file of a printed, or perhaps even copied, hard copy; so, for example, it often uses a forward slash "/" interchangeably with an italicized capital "_I_") and, of course, it is written in Japanese.

But, I too found the lack of any rest between cycles to be "interesting." I will have to look at it again, but unless I missed it, I am pretty sure there is no rest. In addition, the Japanese "maniac" (In Japan, "maniac" is used much like the word "fan," as in: "He is a fan of that sports team." Actually, I believe that the word "fan" comes from "fanatic," so "manic" and "fan" are quite similar. And, I think the word "flashaholic" qualifies just fine as a synonym of "maniac.") who did the testing that I posted made no mention of any rests, except for every 50th test. He simply stated that the "process is repeated." 

I searched for the JIS C8708 standard, mainly because I wanted to make sure that I understood how the "maniac" was conducting his tests which he claimed were being done in accordance with JIS C8708, with the exception of temperature control.

I have no idea what kind of test equipment he has (or has built), but based on that raw data printout tape, I would say that any rests would have warranted some sort of notation there... And, from what I could see, there is no rest.

If we really want to know the answer to this, I am willing to call FDK. I have spoken to them before, and they are (in general) friendly enough. But, they are also extremely close mouthed about Eneloops and any production role that they may have played or still play. It is pretty obvious that they have signed some kind of non-disclosure agreement with Panasonic which prevents them from disclosing even the existence of any non-disclosure agreement. (You can readily understand why it might be a bit embarrassing for Panasonic if the general public were made aware of the fact that those wonderful "Panasonic Eneloop" cells are actually made by Fujitsu. This would greatly enhance the FDK brand image.)

It is a well known fact, however, that the FDK production facility is the true birthplace of the original Eneloops, and from what I have been able to gather, FDK has not been particularly limited by overall production capacity. Therefore, I believe that until this new plant opened in China, FDK has been the sole source of all Eneloops. However, like many other countries, it is far more expensive to manufacture in Japan, than in China. So, as whatever "contract" FDK had (or has) with Panasonic winds down, and Panasonic is free to purchase cells from elsewhere and call them "Eneloop," then, I think we will see more and more Eneloop production moving to China.

I doubt, however, that the Eneloops sold in the Japanese domestic market will ever be made in China. If Panasonic were to attempt that, I believe it would present FDK with a real opportunity to succeed with their own FDK brand cells. The reason is that many (perhaps even most) Japanese consumers prefer products made in Japan, and are willing to pay a premium for products made in Japan. This is really not some "nefarious" plot by the hyper-patriotic Japanese consumer, to prevent the entry of foreign products into Japan. Japanese actually often prefer foreign products, and remain the largest consumers of many premium foreign products. But, only when those foreign products are deemed superior to Japanese products.

The real driving force here, is an innate Japanese preference for enhanced quality, even very incremental differences in quality. Whereas American have a strong tendency to say something is "good enough" (or "good enough," given the lower price), Japanese rarely think that way. Even if they are destitute, and cannot afford better, they will still "endure in silence" until they *can* afford better; they still don't say something is "good enough."

(But, since they think very differently, they end up saying a lot of other things... much of which I disagree with, but I fear I have already taken this thread way, way too far off topic!)




Power Me Up said:


> ...I'm thinking about running another test following that standard as closely as I can. The main difference would be that I won't be keeping to standard lab temperature - unless Panasonic or someone else wants to pay for the electricity bill to run my (Panasonic no less) air conditioner 24/7 for the duration of the test. Would take around 3 months or so for the Eneloop XX cells - maybe around a whole year(!) for standard Eneloops!



Far be from me to stop you from conducting more tests based on JIS C8708, but frankly I don't see what we are going to accomplish. I am readily willing to posit the fact that I will only get 200 cycles, or so, from my Eneloop Pros. I didn't purchase them for their cycles.

Years ago, I purchased a number of what were then considered "top of the line" NiMH cells made by Panasonic. I think they were rated at something on the order of 1200 cycles. I was not yet a "Flashaholic" then, so while I did own a couple flashlights, I mainly used them in various electronic devices. They worked out very well for me, and I am convinced that they have easily paid for themselves, several times over. But, I would be very very surprised if any of them ever even approached 200 cycles. (None of the applications that I was using them in ever had the need for that rapid of discharge and charge rate. If I recharged once a week, that was extremely often.)

My biggest problem with them was their high self-discharge rate. This was especially a problem with flashlights which tended to sit around a lot without being used, but required a fair amount of capacity when needed. If the lights went out (thankfully, not often in Japan) or I needed to go out and look for something in the dark, I usually found that my flashlight went dead on me in a very short time. (The cells were nowhere near fully charged.) So, I ended up having to keep alkalines around for "spares."

But, once I learned about the existence of low self-discharge Eneloops, I realized that they would be a real "game changer" for me. I purchased a number of Eneloop Pro cells (some of which included chargers), and have never needed to purchase another alkaline cell since. (In addition to the cost of alkalines, disposal is a big issue in Japan. All batteries, even alkalines, need to be taken to an authorized recycling center. Believe it or not, some Japanese housewives are not beyond closely examining their neighbors' trash, and if they were to find that you simply threw your alkaline cells in with the regular trash, both you and your family could be "black-listed" for several generations... Slight exaggeration, but you get the idea.)

After I found this forum, I purchased a Maha MH-C9000 and checked all of my old Panasonic NiMH cells. I found that a large number were still in fine shape (around 90% rated capacity), but approximately half had deteriorated significantly, but to varying degrees. I suspect that the major cause of significant deterioration was a mediocre charger, not the number of recharge cycles. In addition, until I had the C9000 to establish reasonably accurate capacities, I was unknowingly mixing 90% capacity cells with 60% capacity cells. Today, I have marked each cell with a color paintmarker so that I can easily determine its current capacity.

So far, every new Eneloop that I have purchased (they are all Pros) has been discharged, run through the "Break-In" process, discharged, and "Analyzed." I try to do this for 8-12 cells at a time, because I then establish matched sets based on capacity. (And, having more cells to choose from at the time of matching, results in better matched sets.) All data from newly purchased cells gets recorded in an Excel spreadsheet, and to the extent possible, I attempt to keep track of which "matched set" went into which application. The cells themselves are not marked, except for a single green dot of paint near the positive terminal. (As you know, it is fairly difficult to mark the black Eneloop Pro cells.)

I have established consistent standards for each color, and should I find at some later date that a cell no longer rates a "green dot," it will receive an additional "blue dot" next to the green. And, so forth: from green, blue, yellow, orange, to red. So far, I only have one of the old Panasonic cells that is marked orange. I have no "reds." And, if my C9000 is ever reluctant to charge a cell due to high internal resistance, I intend to immediately recycle it.

It has been a couple years now since I marked all my old Panasonic cells, and I thought that I would have seen more dramatic changes in capacity, and even recycled some by now. Frankly, I would like to get rid of all those old cells (many of which are AAA) as soon as possible, so I placed quite a number of them in cheap AA adapters and used them in devices that normally require an AA cell. Unfortunately, I have found that they are not so easy to kill off. Perhaps it is because I am rather gentle with my charging (300 mA for AAAs), but they are not yet showing much change in capacity so far. (Unlike most Japanese consumers who are quite willing to throw away perfectly functional items and devices, my conscience will not allow me to recycle then while they are still proving themselves to be perfectly useful... so, I guess I am going to be stuck with them for some time yet.)

So, as crazy as it may sound, having gone to this much trouble, I am actually looking forward to the day when I can place an additional "blue dot" on one of my Eneloop Pros. But, I am fairly certainly that by that time, my blue paint-marker will have dried up, and I will need a new paint marker.

While I have always enjoyed camping and other outdoor activities that required a good flashlight, and I have always admired nice flashlights, I really don't get much chance to use one these days. I have, however, become thoroughly addicted to flashlights (thanks to this forum!) and I now have plenty of them. But, I am simply not a heavy user of discharge recharge cycles. While this may seem highly incongruous with my "investment" in Eneloop Pros, I see good cells as being analogous to ammunition in a firearm. If your handgun holds 14 in a clip, why load it with only 10? (Actually, I once knew someone who did that because they believed it reduced the stress on the magazine spring.) To me, it doesn't make any sense. If I think that there is even a remote possibly that I might need a gun, I want it fully loaded, and I am also going to carry at least two spare clips.

That is why I prefer Eneloop Pros. And, despite their higher cost, I am quite convinced that they are going to easily pay form themselves many times over. So, why not get "the best" in terms of capacity?

By the way, I do I think it is very interesting that other companies such as Turnigy may now be manufacturing good quality, high capacity LSD NiMH cells. Should this forum reach a general consensus that such cells are indeed reasonably consistent and reliable, I would certainly like to try some. But, unfortunately, they do not seem to be available in Japan, and even if they were, so far, it looks likely that they would be priced about the same as Eneloops.


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## Viking (Oct 28, 2014)

Great test as always power me up.

And thanks to Rosoku Chikara for explaining the japanese JIS C8708 endurance test.
I have previously studied it in Japanese my self using google translate for a direct comparison to the IEC standard. And as far as I could tell they was exactly the same , this just confirms it once more.

Power Me Up and Rosoku Chikara as I translate it , JIS ( just as IEC ) only permits rest time every 50 cycle after charge and discharge.

Below are the two respective tests ( the JIS C8708 is a 2013 version ). I guess's Rosoku Chikaras english is a lot better than my japanese 
Maybe he can tell us if he sees any difference between the two tests.


http://kikakurui.com/c8/C8708-2013-01.html
JIS C8708 ( 7.5.1 endurance test)

http://www.cnlumos.com/lumos/Battery Knowledge/Battery Standards/IEC61951-2-2003.pdf IEC ( 7.4.1.1 endurance test)


Power me up IEC also has an official accelerating endurance test procedure as shown in 7.4.1.2 at the link above. Maybe you should give that a closer look


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## Power Me Up (Oct 28, 2014)

Viking said:


> Great test as always power me up.
> 
> And thanks to Rosoku Chikara for explaining the japanese JIS C8708 endurance test.
> I have previously studied it in Japanese my self using google translate for a direct comparison to the IEC standard. And as far as I could tell they was exactly the same , this just confirms it once more.



I can't read the Japanese standard, but I've had a look at the IEC standard that you've linked to.

An interesting difference that I can see between that standard and the test that Rosoku talked about is that the IEC standard says to discharge on cycles 2-48 for only 2 hours and 20 minutes (or if the cell voltage falls below 1.0 Volts) so I would expect that the cells wouldn't be fully discharged on each cycle.

This corresponds well with the text method outlined on the following page:
http://www.large-battery.com/what-is-battery-cycle-life-test.html

I would expect that if the cells aren't being fully discharged on each cycle, they would eventually end up being overcharged in later cycles - unless the charge acceptance was significantly lower than I've seen in the testing that I've been doing... Overcharging isn't good for the cell longevity, so I would expect that it would have a significantly adverse impact on the results...



> Power Me Up and Rosoku Chikara as I translate it , JIS ( just as IEC ) only permits rest time every 50 cycle after charge and discharge.



Thanks for confirming!



> Power me up IEC also has an official accelerating endurance test procedure as shown in 7.4.1.2 at the link above. Maybe you should give that a closer look



Thanks for the links to those files!

It's interesting that for all of the "accelerated" tests, there is a full 24 hour rest on the 49th cycle - seems a bit odd to me if you're wanting the test to run in a reasonably short period of time! 

The testing that I've been doing is closest to 7.4.1.2.3 with the following main differences:

* I'm not doing a 16 hour 0.1C charge for cycle 1.
* I'm not doing the 24 hour rest on the 49th cycle. 
* I'm also discharging down to 0.9V instead of 1.0V 
* I'm giving shorter rest periods.

Looks like the specified ambient temperature is 20 degrees C +/- 5 degrees. Cell surface temperatures are to be kept below 35 degrees C with forced air cooling if required to keep them below that limit.


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## Power Me Up (Oct 28, 2014)

Rosoku Chikara said:


> Far be from me to stop you from conducting more tests based on JIS C8708, but frankly I don't see what we are going to accomplish. I am readily willing to posit the fact that I will only get 200 cycles, or so, from my Eneloop Pros. I didn't purchase them for their cycles.



Mainly out of curiosity, I think it would be nice to confirm that the cells that we buy are actually able to reach the number of cycles that the manufacturers claim when tested with the same methodology.


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## Viking (Oct 29, 2014)

Power Me Up said:


> An interesting difference that I can see between that standard and the test that Rosoku talked about is that the IEC standard says to discharge on cycles 2-48 for only 2 hours and 20 minutes (or if the cell voltage falls below 1.0 Volts) so I would expect that the cells wouldn't be fully discharged on each cycle.



As far as I can tell ( using google translate ) JIS C8708 has the same procedure.
BTW I can recommend translate Japanese word for word , or in very short sentences ( using google translate ) , rather than in long sentences. A little troublesome , but more accurate.



> I would expect that if the cells aren't being fully discharged on each cycle, they would eventually end up being overcharged in later cycles - unless the charge acceptance was significantly lower than I've seen in the testing that I've been doing... Overcharging isn't good for the cell longevity, so I would expect that it would have a significantly adverse impact on the results...




They don't fully charge the cells either. They are charging them for only 3 hours and 10 minutes at a 0,25 C rate. And some of that charge will be wasted energy , not going in to the cell as charge ( thats one the the reasons you can't use charging current to measure capacity ).According to maha as much as 20-30 percent of the charging current could be wasted energy.




> *Quote from the c9000 written manual *( unfortunately I don't have a link )*:
> 
> *
> "Note the charging capacity is usually higher than the actual capacity of the battery owing to some energy lost as heat. Charging capacity cannot be used to judge the performance the battery. Instead, it can only be used to determine the progress of the charger. It is normal for this number to exceed the actual capacity by as much as 20-30%."





> It's interesting that for all of the "accelerated" tests, there is a full 24 hour rest on the 49th cycle - seems a bit odd to me if you're wanting the test to run in a reasonably short period of time!



Actually I didn't noticed that before. I agree that is a little of odd for an accelerating test


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## Mr Floppy (Oct 29, 2014)

Power Me Up said:


> Looks like the specified ambient temperature is 20 degrees C +/- 5 degrees. Cell surface temperatures are to be kept below 35 degrees C with forced air cooling if required to keep them below that limit.



That's a nice broad range, except the force air part, is totally doable without using an air conditioned lab. Perhaps not in Queensland ...


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## Power Me Up (Oct 29, 2014)

Viking said:


> They don't fully charge the cells either. They are charging them for only 3 hours and 10 minutes at a 0,25 C rate. And some of that charge will be wasted energy , not going in to the cell as charge ( thats one the the reasons you can't use charging current to measure capacity ).According to maha as much as 20-30 percent of the charging current could be wasted energy.



The standard specifies charging for 3 hours and 10 minutes and discharging for 2 hours and 20 minutes - that's 190 minutes charging and 140 minutes discharging. Unless the charging efficiency is less than about 74% the cells will be left with an increasing residual charge after each cycle and you would eventually (IMHO) get to the point where the residual charge plus the 190 minutes of charging would overcharge the cells.

Perhaps with regular (non LSD) NiMH cells the charging efficiency is low enough not to overcharge them, but I would expect that Eneloops and other LSD cells would end up being overcharged.

I'm running some tests at the moment which should shed some light on the charging efficiency of Eneloops at low charging rates.


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## Power Me Up (Oct 29, 2014)

Mr Floppy said:


> That's a nice broad range, except the force air part, is totally doable without using an air conditioned lab.



Forced air isn't really hard - just set up a PC case fan above the charger to blow air over the cells all the time...



> Perhaps not in Queensland ...



Definitely not... 25 degrees C just isn't going to happen in QLD over summer without air conditioning! :-( It's not even summer yet, and the temperature in non air conditioned parts of the house is currently at 27 degrees C - and that's at 4pm!


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## Viking (Oct 29, 2014)

Power Me Up said:


> I'm running some tests at the moment which should shed some light on the charging efficiency of Eneloops at low charging rates.



That will be interesting. Let us know about the results.

I have a hard time believing they intentionally will overcharge the cells to a point where it would be harmful ( meaning fewer cycles ).


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## Power Me Up (Oct 29, 2014)

Viking said:


> That will be interesting. Let us know about the results.
> 
> I have a hard time believing they intentionally will overcharge the cells to a point where it would be harmful ( meaning fewer cycles ).
> It is/was my belief these tests are done under the best circumstances possible.



I could be wrong of course...

I suspect that when the standards were originally written, LSD cells hadn't been developed yet, so the cells available at the time had lower charging efficiency and probably weren't being overcharged...

Would be interesting to know if the latest version of the standard has been modified to take into account higher charging efficiencies for LSD cells. Checking the Google translated version, it doesn't appear to have been though...


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## Viking (Oct 29, 2014)

Well thinking about it , they don't let the cells rest much either. That's also not particular healthy , so maybe I could be wrong in my last statement. Maybe they actually don't test under the very best ( most healthy ) circumstances.


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## Rosoku Chikara (Oct 29, 2014)

Power Me Up said:


> Standard laboratory temperature is supposed to be 25 degrees C. I'm not sure what temperature the JIS standard requires though...



JIS C8708:2013 says temperature should be 20 degrees C, +/- 5 degrees...




Viking said:


> ...Below are the two respective tests ( the JIS C8708 is a 2013 version ). I guess's Rosoku Chikaras english is a lot better than my japanese



You have found the same JIS C8708 standard online as I did... not sure why I thought is was the 2007 version. Anyway, it is the same thing as I have been looking at too. My Japanese may indeed be better than yours, but frankly, it is the electrical formulas which are giving me the most trouble... my browser is not rendering the superscript and subscript correctly, and if you look closely you will notice that this standard actually uses "/" in instead of an italicized "_I_" in a large number of places. So, it took me some time to figure out what was going on... (I didn't know the formulas well enough to immediately realize that it should be been read as the "_I_" for discharge current.)

Anyway, in the interests of full disclosure, I was born in Japan, raised in Japan, and have spent the vast majority of my professional career working for Japanese companies. However, I happen to be an American citizen, and I was educated entirely in English, both as a child in Japan, and later on in college in the USA. (My parents were missionaries, and I happened to be born over here.)

I speak Japanese with native fluency, and over the telephone everyone thinks I am Japanese. But, my reading and writing is both limited and slow. However, the advent of the computer age has been of great assistance to me. Not so much due to translation software, because you generally get rather hilarious results when using any kind of machine translation between two languages that differ as much as English and Japanese; but, I benefit greatly from text vocalization software, and from electronic Kanji dictionaries which allow me to rapidly find any Kanji in question. There are thousands and thousands of Kanji, and if you have never had to do so, it may be hard to imagine just how hard it was to even locate the Kanji you wanted in a old fashioned printed Kanji dictionary. 

(In short, there is no way to organize them by sound, because you cannot read them in the first place. Not to mention the fact that most Kanji can be pronounced at least four different ways. Even fairly well educated Japanese frequently cannot read Kanji presented to them. So, if you cannot read them, you certainly cannot find them or list them in alphabetic order, so they use a technique that attempts to organize them according to visual component parts, known as "radicals." Trust me, the new electronic Kanji dictionaries work far better, and are far faster than a hardcopy!)



Viking said:


> ...Maybe he can tell us if he sees any difference between the two tests.



Better than that, I have contacted someone I know at FDK and it turns out that he was involved in this testing procedure in the past. It has been some time ago, so he said he needed to look at the standard and refresh his memory, but in principle, he has agreed to teach us how to conduct the test in the same manner that they do.

He did point out two quick points... He thinks of these tests not as "full" cycle tests, but as "partial" charge, and "partial" discharge tests; with a genuine "full" cycle test every 50 tests. Secondly, he warned me that these tests will take around six months to complete, even for an Eneloop Pro.

While there appear to be some slight differences between the way that the JIS and the IEC stardards are organized, the content certainly appears to be identical. (I have not done a word by word comparison.)

If you guys are really serious about continuing with this "silly" enterprise, I suggest that *Power Me Up *document a proposed test procedure based on the IEC standard, and I will have my contact go over it with me and verify that we are indeed going to conduct the testing in the very same manner that FDK does. (I will also consider sending *Power Me Up* some FDK cells to test.)


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## Viking (Oct 29, 2014)

To my understanding the IEC temperature requirements are the same.



> *7.4.1 Endurance in cycles*
> 
> 
> Prior to the endurance in cycles test, the cell shall be discharged at a constant current
> ...


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## Viking (Oct 29, 2014)

Hi Rosoku Chikara

It was veryinteresting to hear about your origin. I would never had guessed you had American roots 




Rosoku Chikara said:


> Better than that, I have contacted someone I know at FDK and it turns out that he was involved in this testing procedure in the past. It has been some time ago, so he said he needed to look at the standard and refresh his memory, but in principle, he has agreed to teach us how to conduct the test in the same manner that they do.



excellent :thumbsup:


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## Power Me Up (Oct 29, 2014)

Rosoku Chikara said:


> Better than that, I have contacted someone I know at FDK and it turns out that he was involved in this testing procedure in the past. It has been some time ago, so he said he needed to look at the standard and refresh his memory, but in principle, he has agreed to teach us how to conduct the test in the same manner that they do.
> 
> He did point out two quick points... He thinks of these tests not as "full" cycle tests, but as "partial" charge, and "partial" discharge tests; with a genuine "full" cycle test every 50 tests.



Yes, I would agree with this!



> Secondly, he warned me that these tests will take around six months to complete, even for an Eneloop Pro.



That doesn't sound right. Even if the Eneloop Pro does last for 500 cycles, I don't think it would take that long.

The time to do 50 cycles would be: 5.5 hours * 48 cycles plus 32 hours for slow charging plus 1 hour for resting after the 50th charge + 4 hours for 49th discharge + 5 hours for 50th discharge - works out to 306 hours or 12.75 days. Multiply that by 10 lots of tests it works out to about 130 days - assuming that you don't start each test straight away. 130 days is only about 4 months... I suppose in very round figures, that's not that far off from 6 months though! 4th gen standard Eneloops would take about 18(!) months at that rate if they met their rating!



> While there appear to be some slight differences between the way that the JIS and the IEC stardards are organized, the content certainly appears to be identical. (I have not done a word by word comparison.)



I wonder which organisation plagiarised/got inspiration from the other? Having the standards being the same is a good thing IMHO!



> If you guys are really serious about continuing with this "silly" enterprise, I suggest that *Power Me Up *document a proposed test procedure based on the IEC standard, and I will have my contact go over it with me and verify that we are indeed going to conduct the testing in the very same manner that FDK does. (I will also consider sending *Power Me Up* some FDK cells to test.)



That sounds good, but don't go rushing to send them over to me just yet - I don't want you to send them over to me and then not be able to run the testing that you're expecting me to.

There's a bit of work required to get it working and we need to decide if it's going to be close enough to the standard and worth tying up a charger for such a long period... To run the IEC 7.4.1.1 test, I'd need to modify the charger firmware a little to allow for a fixed duration discharge and to also start with a slow charge.

The issues that I see at the moment are the following:


Firmware modifications required. 
Temperatures won't be kept within the testing standard. 
Due to only having a single charging channel, would only be able to test one cell per charger unless I make a compromise:
Allow a rest period after discharging while waiting for the other channel to finish charging (probably not good because the standard doesn't specify allowing a rest other than after the 50th charge and discharge. Would also mean that testing takes longer) 
Charge at 0.5C with (approx) 50% duty cycle. This might affect the charging efficiency and throw out the results. 
 
Charging isn't done with a purely constant current. Due to the use of a buck converter, the actual current will look like a saw tooth pattern. At low charging currents, the current will even drop to zero due to the buck converter operating in non continuous mode. It's possible that the varying current affects the charging efficiency and also therefore how much the cell heats up during charging - again possibly throwing out the results from the test. Would be interesting to do some tests to confirm this one way or the other... On the non LCD model the buck converter operates at 7.8 kHz, so I'm not even sure if that current variations would even be significant. 
Discharging also isn't done with a purely constant current. On the LCD charger, it's done with PWM control - this again may affect the way that the cell heats up during the discharge and affect the results. On the non LCD chargers, I've built a couple of constant current loads, but due to the op amps not being ideal, the current isn't completely constant, so I'm using a bit of PWM to control the current as well. 
During charging, I've got the charger pausing the charge for 0.25 seconds every 5 seconds so that it can read the unloaded voltage on the cell. This could also affect the results - although I wouldn't expect it to be by much. I'm using the pause to get more consistent voltage readings so that I can ensure that termination is accurate. Since all charges for the 7.4.1.1 test are only timed, I could disable the pauses for this test... 

There may of course be other issues that I haven't thought of yet...


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## Rosoku Chikara (Oct 30, 2014)

Power Me Up said:


> ...Temperatures won't be kept within the testing standard...<snip>



Might it not be possible to make a "small test box" that is well insulated and temperature controlled using something like thermoelectric cooling?


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## Rosoku Chikara (Oct 30, 2014)

Power Me Up said:


> ...That doesn't sound right. Even if the Eneloop Pro does last for 500 cycles, I don't think it would take that long...<snip>



I was also a bit taken aback by this statement. I had no idea how much time you must have been spending on some of your tests, so far. The subject had never interested me that much before, so I guess I had in my own mind "preconceived notion" that such "accelerated" testing might be undertaken over a period of days, or at most, weeks...

But, that preconceived notion, was apparently quite wrong. I took a very "brute force" approach to estimating the time required. I actually created an Excel spreadsheet with 500 lines (one for each of the 500 cycles). 

Next, I did my best to estimate the time required for each test on each line (or each cycle). Unless I am mistaken, the charging process takes 3 hrs. 10 mins. (190 mins.) for each cycle, except for every 50th cycle, when it takes 16 hrs. Next, I used the chart posted in my post#14 as guidance as to how long it will take for the cell to reach 1.0 volts. It looks to me like about 290 minutes for the first 50 cycles, then 285 for the next 50, and 280... etc. You don't see a significant reduction in time to reach 1.0 volts until about 350 cycles. 

From there I on, I tried to assume that the cells were just "barely" passing the test (minimum 2 hrs. 20 mins., or 140 mins.). Then, you have the 10 times (once every 50 cycles) where the cell is charged for 16 hrs. and rested for 4 hours, but these are really only minor additions to the overall time that is required.

While I can make no claims of accuracy, my Excel spreadsheet ended up with an estimated total time requirement of 231,233 minutes, or about 5.74 months. So, I realized that my contact at FDK was essentially correct. And, should you decide to undertake this project, you will be making a fairly long term commitment even for Eneloop Pros, much less standard Eneloops.

More Power to You!


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## Power Me Up (Oct 30, 2014)

Rosoku Chikara said:


> Might it not be possible to make a "small test box" that is well insulated and temperature controlled using something like thermoelectric cooling?



They're actually available as a commercial product - you're describing a "camping fridge" - they generally run off of 12V but there are versions that can also run directly off the mains - e.g.
http://www.ebay.com.au/itm/WAECO-TH...=AU_Car_Parts_Accessories&hash=item5d372aa4f5

That's not too bad an idea - would be cheaper than running full air conditioning for months at a time. Worst case scenario for the above unit would be about $50 in electricity to run it flat out for 6 months. In reality, it wouldn't need to run at full power most of the time, so I'd expect it to work out to only be a fraction of that - perhaps $5 to $15 - still more than the cost of the cells that are worn out due to the testing... Unfortunately, they're a bit expensive for something like this - I don't go camping, so it wouldn't be of huge value to me after the testing was complete...


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## Power Me Up (Oct 30, 2014)

Rosoku Chikara said:


> Next, I did my best to estimate the time required for each test on each line (or each cycle). Unless I am mistaken, the charging process takes 3 hrs. 10 mins. (190 mins.) for each cycle, except for every 50th cycle, when it takes 16 hrs. Next, I used the chart posted in my post#14 as guidance as to how long it will take for the cell to reach 1.0 volts. It looks to me like about 290 minutes for the first 50 cycles, then 285 for the next 50, and 280... etc. You don't see a significant reduction in time to reach 1.0 volts until about 350 cycles.



My reading of the IEC standard is that test 7.4.1.1 specifies that for cycles 1 to 48, the cells are discharged for exactly 2 hours and 20 minutes every time - unless they drop below 1.0V in less time. In other words, you can accurately predict that most cycles will take exactly 5.5 hours.


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## Rosoku Chikara (Oct 30, 2014)

Power Me Up said:


> My reading of the IEC standard is that test 7.4.1.1 specifies that for cycles 1 to 48, the cells are discharged for exactly 2 hours and 20 minutes every time - unless they drop below 1.0V in less time. In other words, you can accurately predict that most cycles will take exactly 5.5 hours.



Understood. However, I am not yet entirely certain that that is how Panasonic (and/or FDK) are conducting the test. (Clearly, this is a simple enough question that we can easily get answered when the time comes.)

Having said that, I am not really basing my understanding on any interpretation of either the JIS or IEC standard. The Japanese "maniac" who undertook the testing that I took the liberty of re-posting in my post#14, claims that he was conducting his test according the the JIS standard. If your interpretation were correct, then how could he generate the data required for the following graph?





Based on the above graph, he appears to have generated data which allowed him to say that during the first 300 or so cycles, an Eneloop Pro takes around 280 minutes to reach 1.0 volts.

But, once again, I do not feel that this is an important discussion at this time. Whenever you are "ready," I am convinced that we will be able to get any and all of our questions answered by FDK, such that we can be confident that we are conducting our tests in exactly the same manner that they are.


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## Rosoku Chikara (Oct 30, 2014)

Power Me Up said:


> ...you're describing a "camping fridge" ...Unfortunately, they're a bit expensive for something like this - I don't go camping, so it wouldn't be of huge value to me after the testing was complete...<snip>



In my opinion, a "camping fridge" is a toy. This is what I have recently been "coveting": http://www.engel-usa.com/products/fridge-freezers/engel-mr040-ac-dc-fridge-freezer

I see little benefit from an "camping fridge" because it can only act as a "cooler." Given a high quality ice chest, you can achieve very similar results with ice. (Perhaps the convenience is worth it to some people.) You simply cannot achieve significant efficiency from such solid state devices.

On the otherhand, the above Engel (of Australian design?) can literally (and efficiently) freeze ice in a desert. (Which is rather amazing, in my opinion, and potentially quite useful... ) It uses a unique motorized compressor of Japanese manufacture. Of course, it is a "bit" expensive. But, I must confess, I really want one... :-(

Anyway, what I was thinking was that, given your knowledge of electronics, you might be able to build a relatively low-cost environment controlled box using a heat sensor, a relay, some fans, and a small number of cheap thermoelectric cooling units (thermocouples?). I think one key to minimizing component costs would be to the use of "extraordinary" amounts of insulation. 

(Without the correct temperature, we have little hope of duplicating FDK's tests. You may as well conduct "real world" tests of your own design, and see how well Eneloops perform. Frankly, I doubt that in most "real world" cycle endurance testing that you will ever achieve 500 cycles from an Eneloop Pro. But, why does that matter... I am perfectly satisfied with 200 cycles, which I am fairly confident that my cells will eventually achieve.


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## Power Me Up (Oct 30, 2014)

Rosoku Chikara said:


> Understood. However, I am not yet entirely certain that that is how Panasonic (and/or FDK) are conducting the test. (Clearly, this is a simple enough question that we can easily get answered when the time comes.)



I'd certainly be interested in finding out what they're actually doing in their tests!



> Having said that, I am not really basing my understanding on any interpretation of either the JIS or IEC standard. The Japanese "maniac" who undertook the testing that I took the liberty of re-posting in my post#14, claims that he was conducting his test according the the JIS standard. If your interpretation were correct, then how could he generate the data required for the following graph?



According to my reading of the standard, every 50th cycle is a full charge and discharge, so that would be where he's getting his data from for that graph.

Looking back on the raw data that you posted in post #14, it appears that he was following the standard - D21 terminated at 2 hours and 20 minutes at 1.01V, so it terminated on time rather at the 1.00V termination point. The repeated 2h20m text shown indicates to me that he was discharging for a maximum of 2 hours and 20 minutes each time.


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## Power Me Up (Oct 30, 2014)

Rosoku Chikara said:


> In my opinion, a "camping fridge" is a toy. This is what I have recently been "coveting": http://www.engel-usa.com/products/fridge-freezers/engel-mr040-ac-dc-fridge-freezer
> 
> I see little benefit from an "camping fridge" because it can only act as a "cooler."



The one that I linked to can act as a heater as well, but you're probably right to call it a toy. I wouldn't be surprised if it was designed for light duty intermittent use only - it may well break down in less than 6 months of continuous use...



> Given a high quality ice chest, you can achieve very similar results with ice. (Perhaps the convenience is worth it to some people.) You simply cannot achieve significant efficiency from such solid state devices.



Efficiency was one of my first concerns when you suggested the idea. To run something for 6 months, I'd be looking for convenience ahead of efficiency.



> On the otherhand, the above Engel (of Australian design?) can literally (and efficiently) freeze ice in a desert. (Which is rather amazing, in my opinion, and potentially quite useful... ) It uses a unique motorized compressor of Japanese manufacture. Of course, it is a "bit" expensive. But, I must confess, I really want one... :-(



It does look pretty cool - I agree! 



> Anyway, what I was thinking was that, given your knowledge of electronics, you might be able to build a relatively low-cost environment controlled box using a heat sensor, a relay, some fans, and a small number of cheap thermoelectric cooling units (thermocouples?). I think one key to minimizing component costs would be to the use of "extraordinary" amounts of insulation.



I'm actually more of a software guy myself. I can use (and have) a soldering iron, but I wouldn't claim to be an expert in building things - I'd rather spend the money and buy something commercially available if possible.

Extraordinary amounts of insulation would only help up to a certain point - keep in mind that all of the power going into the charger will eventually end up as waste heat inside the box and would need to be removed by the cooling system.



> (Without the correct temperature, we have little hope of duplicating FDK's tests. You may as well conduct "real world" tests of your own design, and see how well Eneloops perform. Frankly, I doubt that in most "real world" cycle endurance testing that you will ever achieve 500 cycles from an Eneloop Pro. But, why does that matter... I am perfectly satisfied with 200 cycles, which I am fairly confident that my cells will eventually achieve.



I agree that running these sorts of tests is largely academic. For the most part, I'm interested in doing these sorts of tests just to satisfy my own curiosity. I think that there is some utility though in being able to say which cells are actually capable of performing well over a large number of charge cycles. Although your Eneloop Pros may (or may not!) last for 200 cycles, I suspect that by then, they probably won't be performing anywhere near as well as when they were new, so you might decide to retire them before they hit the 200 cycle mark...

I'm thinking about running some different types of tests in the future to answer other questions that I have. E.g. what things can you do to cause Eneloops to fail sooner. Knowing the answer to that question will help myself (and others) know what things to avoid so that our Eneloops can last to their full potential. Again, it's still mostly academic since Eneloops are so robust, I'd expect that most of them will last for decades even if they're not being treated the best...


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## Rosoku Chikara (Oct 30, 2014)

Power Me Up said:


> ...Although your Eneloop Pros may (or may not!) last for 200 cycles, I suspect that by then, they probably won't be performing anywhere near as well as when they were new, so you might decide to retire them before they hit the 200 cycle mark...<snip>



The question to which I might want to know the answer is: "How may cycles (full or nearly full) cycles can I potentially expect from my Eneloop Pros?"

My home is not maintained at a steady 20 degree C temperature. Right now, things are not too bad, but in the past (when I was living elsewhere) I had to deal with serious concerns with my computers overheating in my home.

Personally, I am more interested in having conduct testing that approximates "real life" use of Eneloop cells. When it comes to standard cells, I have little doubt that most users will never, ever, get very close to approaching the claimed 2100 cycles. But, in the case of Eneloop Pros, some people might eventually experience a problem.

While I am more than happy to assist you in establishing a test procedure that is identical to that use by FDK, I think it likely that I (and other like me) might benefit as much (or more) from some more realistic testing (not to any standard). The one reason that springs to my mind where you might want to actually duplicate FDK's testing proceedure is to verify whether or not your "laboratory" equipment is capable of achieving results that are similar to theirs...


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## Power Me Up (Oct 30, 2014)

Rosoku Chikara said:


> The question to which I might want to know the answer is: "How may cycles (full or nearly full) cycles can I potentially expect from my Eneloop Pros?"



That's the sort of thing that I'd like to be able to answer with this type of testing.

Unfortunately, there are so many variables when it comes to real world use, that it's impossible to come up with a standardised test that will give a definitive answer. The best that we can hope for is some test results that can give us a reasonable idea of what that would be under various circumstances.



> My home is not maintained at a steady 20 degree C temperature. Right now, things are not too bad, but in the past (when I was living elsewhere) I had to deal with serious concerns with my computers overheating in my home.



I've seen computers having problems in high temperatures here in QLD Australia, so you're not alone!



> Personally, I am more interested in having conduct testing that approximates "real life" use of Eneloop cells. When it comes to standard cells, I have little doubt that most users will never, ever, get very close to approaching the claimed 2100 cycles. But, in the case of Eneloop Pros, some people might eventually experience a problem.



I'd say that you're probably right there - people are more likely to wear out their Eneloop Pros than the regular Eneloops because of the reduced number of usable cycles. It'd still be possible to wear out the regular Eneloops, but I agree that most people will probably never use them enough to get to that point...



> While I am more than happy to assist you in establishing a test procedure that is identical to that use by FDK, I think it likely that I (and other like me) might benefit as much (or more) from some more realistic testing (not to any standard). The one reason that springs to my mind where you might want to actually duplicate FDK's testing proceedure is to verify whether or not your "laboratory" equipment is capable of achieving results that are similar to theirs...



Agreed. That's why I went with my own testing method to try to get through as many cycles as quickly as possible - just to be able to compare different brands of cells, etc. Since I'm not following any official standard, I can't really compare my results directly with the official ratings.

It would be interesting to run the standard test to see if I can get similar results to the manufacturer. Unfortunately, even following the standard to the letter may not be good enough to get the same results even if the equipment is perfect and follows the standard to the letter. I think that there is enough wiggle room in the standard that you could (intentionally) affect the results in a favourable way. I think that it's reasonably certain that heat isn't good for batteries - the standard allows for a temperature range of 15 to 25 degrees C. If one test was done at 15 degrees C and another was done at 25 degrees C, I'd expect there to be a fairly significant difference in the results. If you added forced cooling whilst running the air temperature at 15 degrees C, I'd expect the difference to be even greater!

In other news, I just took delivery of an 8 pack of Chinese made "Chocolat" AA Eneloops. (Cost me a whole $1.98 including delivery!) Checking the back of the pack, it says: Battery life based on testing method established by IEC61951-2 (7.5.1.3) (varies according to conditions of use)

Unfortunately, I can't find a 7.5.1.3 in the IEC standard previously linked and I can't see anything relevant in the Google translated version of the JIS standard...


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## Viking (Oct 31, 2014)

Power Me Up said:


> In other news, I just took delivery of an 8 pack of Chinese made "Chocolat" AA Eneloops. (Cost me a whole $1.98 including delivery!) Checking the back of the pack, it says: Battery life based on testing method established by IEC61951-2 (7.5.1.3) (varies according to conditions of use)
> 
> Unfortunately, I can't find a 7.5.1.3 in the IEC standard previously linked and I can't see anything relevant in the Google translated version of the JIS standard...



The latest edition of the IEC standard can apparently be purchased from IEC it self at this link:
http://webstore.iec.ch/Webstore/webstore.nsf/ArtNum_PK/45161!opendocument&preview=1

But I think this indian Standard version below is identical to IEC. 
Notice in the upper corner at every page it says: *"IS 16048 (Part 2) : 2013*
* IEC 61951-2 : 2011”*

And in the forewords it says "This Indian Standard (Part 2) which is identical with IEC 61951-2 : 2011"

This apparent later IEC version from 2011 has 7.5.1.3 included at page 12. 
7.5.1.3 is some minimum cycle life requirements.

https://law.resource.org/pub/in/bis/S05/is.16048.2.2013.pdf


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## Power Me Up (Oct 31, 2014)

Viking said:


> The IEC standard can apparently be purchased from IEC it self at this link:
> http://webstore.iec.ch/Webstore/webstore.nsf/ArtNum_PK/45161!opendocument&preview=1
> 
> But I think this indian Standard version below is identical to IEC.
> ...



Well spotted Viking! 

Looks like that's the same test as the 7.4.1.1 in the other document.

I just pulled out an unopened pack of Tropical AA Eneloops (3rd Gen Japanese made) and checked the back of the packaging - it says:

Battery life based on testing methods established by IEC61951-2 (7.4.1.1) (Varies according to conditions of use)

So... It looks like the Chinese Eneloops are rated with the same method as the 3rd Gen Japanese Eneloops - just the test number has been changed with the updated version of the standard...


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## Rosoku Chikara (Oct 31, 2014)

Power Me Up said:


> ...every 50th cycle is a full charge and discharge, so that would be where he's getting his data from for that graph...<snip>



Yes, that would explain the data, so I stand corrected. Your interpretation is no doubt correct. I guess my contact at FDK was either exaggerating some, or thinking in terms of testing the standard capacity cells.

No hurry, but when you are ready, let me know when (and how) you wish me to proceed. I believe I will be able to get all our questions answered.


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## Power Me Up (Oct 31, 2014)

Rosoku Chikara said:


> No hurry, but when you are ready, let me know when (and how) you wish me to proceed. I believe I will be able to get all our questions answered.



If your contact is willing to divulge some details, I'd like to know what the actual temperature was kept at for their testing? Also, did they use forced air to help keep the cells cool? As I mentioned earlier, it wouldn't surprise me if running at the minimum temperature and with constant air cooling would help the cells to last longer, so I'd be curious if they actually did that.

I'm currently thinking that it might be worth running a test on a couple of cells even without keeping the temperature constant - just as a comparison to the testing that I've been doing previously just to see if the cells do tend to last longer with a different testing method.

I'll need to do some more testing first to see how charging efficiency is affected by doing the charging in slightly different ways as I previously mentioned...


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## bcwang (Oct 31, 2014)

Power Me Up,

You had good answers to all my points so I'm not going to bother quoting them. I'm still wondering about the huge inconsistency in the XX cells, even if the slightly higher capacity is the reason they don't outlast the turnigy cells in number of cycles. I have some questions that may jog more conversation.

- You are terminating the discharge at 0.9v but is this as measured under load or during a pause? If during a pause, the cells may be over discharged.

- This version of the charger isn't able to do constant discharge current I thought, isn't it only able to drain through a resistor? Or am I mistaken and you can control the current very well? If the current is just based on cell voltage, if the XX cells hold higher voltage under discharge than the Tunirgy, they are also discharging at a higher rate and thus under harder conditions.

- To answer one of your questions, the voltage profile of eneloops seems to be higher than some other nimh cells in the regard that they are at a higher voltage. In the MH-C9000 charger for instance, some brands of cell can terminate on -delta V, while Eneloops always end on peak V limit of 1.47v. Maybe most Nimh behave like eneloop and it's the few outliers that are lower voltage. But it is known that the C9000 never terminates on -delta V for eneloop.

- The graphs you generated of the voltage and temp during charging, are those voltages measured under charge load or during pauses between charge pulses? The reason I ask is the C9000 measures during a pause and ends charge termination at 1.47v. Your charts show voltages up around 1.52v. If they were measured the same way, the inflection point termination is definitely ending much further beyond where the C9000 ends it's charge. I'm not saying it's over charging since the c9000 is undercharging eneloops and has to depend on a top-off 100ma 2 hour charge to fill up the rest of the cell. But I wonder if handling the top off gently like that leads to prolonged cell life. 

-The cell temperature in that graph, where is the measurement point? If it's a thermistor only contacted by conduction through a charge terminal, the actual cell temp may be much hotter. I'm just trying to get a gauge of how much earlier your inflection point algorithm is ending the charge compared to when the cell temps start to really rise.

-Does the charger/discharger contribute any heat that may be influencing cell temperature?

- With this analyzer you have - I think a potentially valuable test would be to compare life cycles if you only drain to 1v rather than 0.9v under load and see if it improves cell life greatly. You could also have variations which may showcase how nimh life can be greatly improved (or not) by avoiding full charge and full discharge:
0.9v discharge cutoff - full charge
1.0v discharge cutoff - full charge
0.9v discharge cutoff - 90% charge (maybe with peak voltage termination to hopefully hit before any of the other termination methods)
1.0v discharge cutoff - 90% charge

-An unrelated topic but for your firmware - Maybe a mode that can end charge earlier (maybe by customizable peak voltage) with hopes that it can increase cycle life. Kind of like li-ion where partial charge and discharge net far better life. I'm not sure with Nimh chemistry if the full charge chemical process helps keep the chemicals more balanced for longer life. But if there is no benefit to a full charge and only risk with extra heat and wear, a charge less than full may be a great contributor to battery life and I can believe many people don't need the full capacity of the battery and would prefer longer cycle life. Test evidence that this helps batteries last would really seal the deal for the need for this kind of feature in a charger.

I'm actually a backer of the lcd version of the charger so I'm really looking forward to using it!


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## Bright+ (Oct 31, 2014)

Power Me Up said:


> It seems that increased internal resistance is the cause of these failures and in this case it has happened before much capacity has been lost.
> 
> The cells are still usable with good capacity for low current devices.


Yeah, that's my experience too. Once this problem develops, they'll usually get rejected by the charger. If normal chargers will no longer charge them, I consider them done.


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## Power Me Up (Nov 1, 2014)

bcwang said:


> I'm still wondering about the huge inconsistency in the XX cells, even if the slightly higher capacity is the reason they don't outlast the turnigy cells in number of cycles. I have some questions that may jog more conversation.



Yes, I'm still wondering about the inconsistency as well - I think it's worth running more tests for! 



> - You are terminating the discharge at 0.9v but is this as measured under load or during a pause? If during a pause, the cells may be over discharged.



Termination is at 0.9V under load.



> - This version of the charger isn't able to do constant discharge current I thought, isn't it only able to drain through a resistor? Or am I mistaken and you can control the current very well? If the current is just based on cell voltage, if the XX cells hold higher voltage under discharge than the Tunirgy, they are also discharging at a higher rate and thus under harder conditions.



The non LCD charger can't control the current into an external load, but can use PWM to control the current into the internal load. Unfortunately, the internal load can't maintain a high current as the cell voltage decreases, so what I've done is to build a constant current load (actually 2 of them) for use with the non LCD charger. Unfortunately, the fact that op amps in the real world don't work exactly the same as an ideal op amp should, the current isn't perfectly constant, so I'm using PWM through the internal load to regulate the discharge current. I'm able to maintain the current with fairly good consistency this way.

The LCD charger is able to use PWM on both the internal and external loads, so I'm just using power resistors on that charger.

I have had some problems with contact resistance on the connections for the external loads, so there have been times where the actual current has been lower than desired.



> - To answer one of your questions, the voltage profile of eneloops seems to be higher than some other nimh cells in the regard that they are at a higher voltage. In the MH-C9000 charger for instance, some brands of cell can terminate on -delta V, while Eneloops always end on peak V limit of 1.47v. Maybe most Nimh behave like eneloop and it's the few outliers that are lower voltage. But it is known that the C9000 never terminates on -delta V for eneloop.



I agree that Eneloops charge to higher voltages than at least some other NiMH rechargeables. I don't see that as a reason to think that inflection termination wouldn't work correctly though.



> - The graphs you generated of the voltage and temp during charging, are those voltages measured under charge load or during pauses between charge pulses? The reason I ask is the C9000 measures during a pause and ends charge termination at 1.47v. Your charts show voltages up around 1.52v. If they were measured the same way, the inflection point termination is definitely ending much further beyond where the C9000 ends it's charge. I'm not saying it's over charging since the c9000 is undercharging eneloops and has to depend on a top-off 100ma 2 hour charge to fill up the rest of the cell. But I wonder if handling the top off gently like that leads to prolonged cell life.



If I recall correctly, someone else did some cycle testing on regular Eneloops in a C9000 and they didn't actually get that many cycles out of them before the C9000 rejected them. I'll have to see if I can find that post - I think that it was here on CPF. Might even be worth repeating the test myself. I suspect that even though the main charge on the C9000 undercharges Eneloops, the top off charge ends up overcharging them a little - it has been speculated that any overcharge - even at low rates is bad for low self discharge cells...



> -The cell temperature in that graph, where is the measurement point? If it's a thermistor only contacted by conduction through a charge terminal, the actual cell temp may be much hotter. I'm just trying to get a gauge of how much earlier your inflection point algorithm is ending the charge compared to when the cell temps start to really rise.



Yes, the temperature sensor is mounted on the PCB near the negative terminal of each cell, so the heat is transferred by conduction from the cell holder. I agree that the cell temperature is most likely somewhat higher than the sensor is able to read.



> -Does the charger/discharger contribute any heat that may be influencing cell temperature?



That's a very good question! Unfortunately, yes, it does. I don't think that any charger (commercial or otherwise) will be able to charge cells without transferring some heat from the charging circuitry to the cell being charged - short of a specialised test setup at least...

It is a good point that I should have thought of when I was making my list of possible differences between the test that I can run and how Sanyo/Panasonic/FDK run their tests. If I was running this sort of test commercially and wanted to get the maximum number of charge cycles out of the test, I'd be doing my best to isolate the cells from any external heat source such as the charging circuitry. I suspect that they're probably doing that - would be interesting if Rosoku could confirm!

For the testing that I have been doing, the heat transfer from the charging circuitry could be one of things causing the most affect on the results! At least if I was to run testing according to the IEC standard, there would be a lot less heat being generated at 0.25C rates...



> - With this analyzer you have - I think a potentially valuable test would be to compare life cycles if you only drain to 1v rather than 0.9v under load and see if it improves cell life greatly. You could also have variations which may showcase how nimh life can be greatly improved (or not) by avoiding full charge and full discharge:
> 0.9v discharge cutoff - full charge
> 1.0v discharge cutoff - full charge
> 0.9v discharge cutoff - 90% charge (maybe with peak voltage termination to hopefully hit before any of the other termination methods)
> 1.0v discharge cutoff - 90% charge



Yes, I think that makes a lot of sense - I've actually already been thinking along those lines myself. The first test I'm planning to do along these lines is to terminate both charging and discharging early and see how much of a difference that makes. Later on, I'll run separate tests where only either the charge or discharge is incomplete. My current thoughts are to terminate charging at something like 1.40V to 1.44V and to terminate the discharge at 1.1V - it'll be interesting to see how much of a difference this makes on the total number of cycles that can be achieved.

I've got high expectations that doing this will make a significant difference. From what I've heard, Toyota was limiting both the discharge and charge levels on the NiMH cells in the Prius to increase cell longevity. I would expect that they would only do this if they knew that is was going to significantly increase the cell life of their packs, otherwise, they'd just use smaller packs and use their full capacity. Using smaller packs would not only reduce production costs, but it would also reduce total weight which would improve fuel efficiency even further, etc. It might be though that their reason for doing that is purely to make it less likely that individual cells in the packs aren't being reverse charged and overcharged since that would kill the packs relatively quickly and that the benefit for individual cells isn't particularly great at best.



> -An unrelated topic but for your firmware - Maybe a mode that can end charge earlier (maybe by customizable peak voltage) with hopes that it can increase cycle life. Kind of like li-ion where partial charge and discharge net far better life. I'm not sure with Nimh chemistry if the full charge chemical process helps keep the chemicals more balanced for longer life. But if there is no benefit to a full charge and only risk with extra heat and wear, a charge less than full may be a great contributor to battery life and I can believe many people don't need the full capacity of the battery and would prefer longer cycle life. Test evidence that this helps batteries last would really seal the deal for the need for this kind of feature in a charger.



Yes, you can actually already do that with the current firmware if you want to.



> I'm actually a backer of the lcd version of the charger so I'm really looking forward to using it!



Thanks for being a backer! Hopefully it won't be too much longer before Paul is able to send a charger your way!


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## Rosoku Chikara (Nov 7, 2014)

Power Me Up said:


> ...I'd like to know what the actual temperature was kept at for their testing? Also, did they use forced air to help keep the cells cool? As I mentioned earlier, it wouldn't surprise me if running at the minimum temperature and with constant air cooling would help the cells to last longer, so I'd be curious if they actually did that...<snip>



I was told that their tests were conducted under laboratory conditions with an aim point of 20 degrees C, and certainly well within the +/- 5 degree standard. He said however, that he believes the actual temperature was much closer to +/- 1 or 2 degrees (or between 18 - 22 degrees C).

Temperature was controlled by environmental air conditioning only. No fans or "constant air cooling" was used.


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## Power Me Up (Nov 7, 2014)

Rosoku Chikara said:


> I was told that their tests were conducted under laboratory conditions with an aim point of 20 degrees C, and certainly well within the +/- 5 degree standard. He said however, that he believes the actual temperature was much closer to +/- 1 or 2 degrees (or between 18 - 22 degrees C).
> 
> Temperature was controlled by environmental air conditioning only. No fans or "constant air cooling" was used.



That's good to know - thanks!

Did they keep the cells separate from any potential heat sources - e.g. charging circuitry?


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## Viking (Nov 7, 2014)

Rosoku Chikara said:


> Temperature was controlled by environmental air conditioning only. No fans or "constant air cooling" was used.



Interesting.
Only one more thing I would have liked to know is if they allow cell temperature to rise above 35 degrees during the test. As far as I understand , forced ventilation is just an option to keep cell temperature under 35 degrees celsius if necessary.


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