# Your advise on Eneloop first charge



## tino_ale (Sep 27, 2007)

Hi all,

I've got brand new Eneloop to charge, haven't used them at all (so they must be about 80% charged already).

I have a Maha C9000 in the air and I would like to know your advise about first charge :

I would like 1. to charge the batts and 2. to know their capacity

My idea is to :
1/ charge at 1.5Amps (0.75C) the remaining capacity
2/ discharge at 1.5amps (and get the actual capacity number)
3/ recharge completely at 1.5amps in order to use them

OR I could simply :
1/ discharge at 1.5 amps without prior charge
2/ recharge at 1.5amps and look at the capacity the batts have accepted

OR I could (I would prefer to avoid that one, too long):
1/ discharge
2/ charge
3/ discharge (and get the capacity number)
4/ charge

How do you think about that? Are my charge/discharge numbers good? 0.75C is just between 0.5-1.0C wich is the recommenced charging rate for Ni-MH, so I guess it's good?

I don't have time to make slow charge like 16 hours...

Thanks for reading


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## Power Me Up (Sep 27, 2007)

The maximum discharge rate on the C9000 is 1 amp, so keep that in mind.

As far as cell performance goes, it doesn't seem to matter too much what you do with Eneloops when it comes to the first charge - they don't seem to need a forming charge like most other NiMH cells.

If you're really in a rush to use them and not tie up your C9000 for too long, just charge them up and use them. If you're curious about their initial out of the packet capacity, you could do the initial discharge before charging them, otherwise put them straight on to charge. I charge mine at 1 amp, but 1.5 amps should be fine as well. After the first charge, you can do a discharge test to find their baseline capacity, but again, you should only do that if you're curious as to their actual capacity - this could be useful for comparison later on down the track to see if their capacity has degraded with use, but otherwise isn't really that important...


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## NiOOH (Sep 27, 2007)

What I do is discharge them to check remaining capacity. Eneloops have a date code, so I am just interested to know what is their remaining capacity. I do this at 0.2C or 400 mA. 
Then I run "Refresh and Analyze" cycle at 1 Amp charging and 400 mA discharging to get their "as new capacity". After that I consider them ready to eneter service.
As it has been said, the Eneloops appear to be fully formed and do not benefit from this initial cycling. I only do it to get some basic information about them.


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## tino_ale (Sep 27, 2007)

Ok I got it. Thanks!

Because I'm curious about their initial performance, I will :

1. Charge them full @ 1.5amps
2. Discharge at 1Amp
3. recharge them full for use

I know discharging at 1amps will not give the highest capacity but I want to know what is their performance at this (still very reasonnable) 0.5C.

Thank again, looks like these Eneloop are no-brainers :thumbsup:


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## Turak (Sep 27, 2007)

Go take a look at this thread....

https://www.candlepowerforums.com/threads/175350


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## tino_ale (Sep 29, 2007)

I've received my Maha-C9000 and run R&A 1A/1A on these new Eneloop.

I'm slightly dissappointed by heat builtup for the Eneloops discharging at 1A, it's only 0.5C but they get warmer than I expected. Still very acceptable though...

Other than that, I was surprised that the C9000 read only 1.15-1.18V after only 1000mAh under a 1A load, considering that the batts gave about 1900mAh in total, I find that number quite low.

Could the fact that it is their first discharge explain the relatively low voltage under load?

In fact, during first charge, the charger could only put about 100-130mAh before terminating charge.

The 1900mAh total capacity is not bad at all IMO, considering the fact that it's their first discharge, and at 1A.


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## Turak (Sep 29, 2007)

Keep in mind.....

When comparing the capacity of the batteries, ALWAYS use the .2C rate (for Eneloops 400mA). Otherwise your numbers are inaccurate for comparison to anyone using a different rate.

If you were reading the voltage off the MH-C9000 display ....... well....let's just say that it can be somewhat deceiving.

---------------------------------------------------------------------------------
Section Regarding discharge method/rates removed until further testing can verify....
---------------------------------------------------------------------------------

Another thing.....while the batteries can be charged/discharged using a variety of rates, the rates that produce the least amount of heat, generaly speaking, are going to give the battery its longest possible life.

While many battery manufacturers set the fail-safe charger cutoff points at anything from 145'F to 160'F....I am finding that anything above about 120'F starts cutting into the overall amount of cycles you will get out of the battery. This pretty much means that nailing that initial end of charge termination signal is CRITICAL for the overall longevity of the battery, because over charging is definitely bad in the long run.

My point is that while you may be able to charge the Eneloops and any other battery at .5C and 1C.....the 1C rate is going to generate more overall heat than charging them at the .5C rate and therefore cut into the number of overall cycles you will ultimately get out of the battery.

It seems that many have taken the opinion that you 'need' the higher rates so the charger sees the end of charge voltage variations and is able to properly terminate the charge. While this was definitely true with the earlier MH-C9000's, it is not nearly as bad with the 'improved' MH-C9000's. I still think that they need to work on the properly terminating the charge using lower rates just a bit more though and especially with the lower capacity cells (Ni-Cd's).

Some will insist that you need to charge them at .5C to 1C rate. This is not totally true. If you are using the early MH-C9000's, then probably yes more so, because of its sometimes marginal ability to terminate properly at the lower rates. But, if you are using the later MH-C9000's or other chargers that do not have the problems terminating properly at the lower rates, then using the lower rates WILL give you more cycles out of the battery in the long run. Granted this assumes you have the time.

Look at the Sanyo charger (MQN05U) that comes with the Eneloops, charges them at 300mA and does not seem to have any problems terminating the charge properly. As a matter of fact, look at MOST of the chargers out on the market and they tend to stay at the 1A or lower rates. Granted part of it is the cost. But early on the push was longevity, now its more for speed.

Many manufacturers as of late, seem to be bending to the public demand of wanting the faster charging, sacraficing overall performance as a result. You notice that the manufacturers sure don't go out of their way to explain that using the faster charging is going to give you less cycles. I think this is one of the reasons that many try the so called 'quick' chargers, get less than optimal performance from a set of rechargables, and switch back to alkaline.

Probably the absolute WORST charger on the market right now is the Energizer 15 minute charger. Cooks the batteries at a blistering 7.5A. Tested some Energizer 2500's on it.......got between 75-100 cycles before it totally ruined the 8 test batteries. I would be amazed if you can even get 200 cycles out of any battery using that charger. But hey, the battery manufacturers probably kinda like that, means you have to buy more batteries.

AN UNINFORMED USER IS A BATTERIES BIGGEST ENEMY, HEAT IS SECOND! (hehe)


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## Power Me Up (Sep 30, 2007)

Turak said:


> The MH-C9000 is REALLY applying a 2A load no matter what setting you set it on. It just uses a duty cycle method that averages it out.
> 
> For example....when you set it on the 1A discharge rate. It REALLY is discharging it at 2A using a 50% duty cycle, which in theory would give you a 1A discharge rate.


Actually, I'm pretty sure that the C9000 puts a 1A load on cells when doing a discharge since that is the maximum discharge rate that can be selected.



> My point is that while you may be able to charge the Eneloops and any other battery at .5C and 1C.....the 1C rate is going to generate more overall heat than charging them at the .5C rate and therefore cut into the number of overall cycles you will ultimately get out of the battery.


 Keep in mind though that if you're charging at 1C, the termination may occur sooner, so the cell may spend less time being heated and so actually reach a lower maximum temperature.

I'm not sure that is actually the case though - it'd be something that would be interesting to test.

That said, I generally use the default 1A charge rate on my C9000s without any problems - 0.5C on my Eneloops, but less than 0.5C on my Sanyo 2700s.




> Probably the absolute WORST charger on the market right now is the Energizer 15 minute charger. Cooks the batteries at a blistering 7.5A. Tested some Energizer 2500's on it.......got between 75-100 cycles before it totally ruined the 8 test batteries. I would be amazed if you can even get 200 cycles out of any battery using that charger. But hey, the battery manufacturers probably kinda like that, means you have to buy more batteries.


Actually, the Energizer 2500s have a very bad reputation for failing quickly - If you got 75 cycles out of them, you probably did a lot better with them than a lot of other people.

I don't have a 15 minute charger myself - I don't really see the point. The beauty of Eneloops is that if you've got enough of them, there's no need to be in a rush to charge them since you can charge them well in advance of when you need them. The exception to this of course would be for people who use a LOT of cells every day - still probably better to get several slower chargers IMHO, but each to their own of course!


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## Burgess (Sep 30, 2007)

to *Turak* and *Power Me Up* --


Great info you've posted. 


Thank you for sharing. :twothumbs



Just bought a Maha C-9000 charge/analyzer myself,
and appreciate the specifics.



BTW, what is the NEWEST "date-mfg code" that anyone has *ever seen* on Sanyo Eneloops ?


Myself, i've never seen *anything* other than 2006.



Isn't this strange ?



_


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## tino_ale (Oct 1, 2007)

The code "07-06LJ" is stamped on mine, bought Sept.07 in Japan (if that matters).


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## SilverFox (Oct 2, 2007)

Hello Turak,

A point of clairifacation...

The reason it is recommended to charge NiMh cells at a rate in the 0.5 - 1.0C range is to insure a consistent end of charge termination signal. This results in minimal temperature rise in the cell and long cycle life.

You can charge at lower rates, but as the cell ages, the termination signal seems to drop off and in some cases it disappears. A charger with a low charging rate can miss the end of charge termination and continue to charge until the secondary timer shuts the charger off. This may not kill the cell through high temperature, but will kill it through separator dry out.

The exception to low charging rates is the 0.1C rate. The cell seems to be able to endure overcharging at this rate with minimal damage. However, if you go above this rate, you run into problems.

The chargers that come bundled with packs of batteries seem to be left over NiCd chargers with a slight modification in termination value or timer settings. These chargers are cheap to include, but they do not provide optimum results.

The 15 minute chargers were designed around 2200 - 2300 mAh cells. I have 150 cycles on some 2000 mAh cells and they are still at about 91% of their initial capacity. I don't share your belief that it is one of the worst chargers around, but I don't recommend it for higher capacity cells. My 2500 mAh cells ended up with only about 60% of their initial capacity after 150 cycles.

Tom


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## Turak (Oct 2, 2007)

Hi Silverfox,

Let me say that I agree with everything you say in this post, although I have some different opinions on the reasons behind some of the points you made. As long as we are 'clarifying' some things, let me offer some other possibilities.




SilverFox said:


> The reason it is recommended to charge NiMh cells at a rate in the 0.5 - 1.0C range is to insure a consistent end of charge termination signal. This results in minimal temperature rise in the cell and long cycle life.


 
The reason it is recommended to charge NiMh cells at a rate in the 0.5 - 1.0C range is because it is *easier* to consistently sense the end of charge termination signal which allows the manufacturers to build the cheapest possible charger, _although usually at a sacrifice in the overall usable life of the cell_. 



SilverFox said:


> You can charge at lower rates, but as the cell ages, the termination signal seems to drop off and in some cases it disappears. A charger with a low charging rate can miss the end of charge termination and continue to charge until the secondary timer shuts the charger off. This may not kill the cell through high temperature, but will kill it through separator dry out.
> 
> The exception to low charging rates is the 0.1C rate. The cell seems to be able to endure overcharging at this rate with minimal damage. However, if you go above this rate, you run into problems.


 
This is only a problem if you build a charger and try to get by using the easiest, cheapest methods (i.e. -deltaV and timer) to end the charge. Invest a little more in to the design and use additional methods to sense the end of charge and you can charge a cell at almost any lower rate you want...within practical limits.

Even the .1C rate or a trickle charge for that matter, will eventually damage/dry out the separator, or even worse cause dhendrite/larger crystal formation over extended periods of time.



SilverFox said:


> The chargers that come bundled with packs of batteries seem to be left over NiCd chargers with a slight modification in termination value or timer settings. These chargers are cheap to include, but they do not provide optimum results.


 
Leftovers, not at all....they are perfectly new chargers, built with the concept of making it as cheap as they possibly could while still producing a product that is marketable to the consumer, while causing a minimum of complaints.

Interesting thing to note.....I have been testing the MQN05 charger that Sanyo bundles with their Eneloops. This one charges at 300mA rate for AA's. I have tried 2000, 2300, and 2500mA NiMH, along with some 600, and 1000mA NiCd's. So far, the thing has not missed a single end of termination yet.

So....why is it that Sanyo has no problem charging batteries at the 300mA rate?




SilverFox said:


> The 15 minute chargers were designed around 2200 - 2300 mAh cells. I have 150 cycles on some 2000 mAh cells and they are still at about 91% of their initial capacity. I don't share your belief that it is one of the worst chargers around, but I don't recommend it for higher capacity cells. My 2500 mAh cells ended up with only about 60% of their initial capacity after 150 cycles.


 
The rub there is that it WAS ESPECIALLY DESIGNED with the higher capacity cells in mind. All that capacity took too long at the slower rates, they started getting consumer complaints....we want faster...we want faster.  So they gave you faster....._didn't bother telling you that you could kiss your 500 or 1000 cycles goodbye_....did they?

My experience has shown that almost any 2000mA battery will out perform almost any of the 2500mA and above batteries when it comes to 'abusing' them. YES ABUSING. Charging a 2500mA cell at a 7500mA (cmon that's 3C on an AA cell) rate is exactly that.

Does it work......yes. Is it good for the battery....definitely not.

You may get away with it using some newer cells that are in very good shape...but at the very least you are ultimately going to cause the internal resistence of that battery to skyrocket and then start producing heat at a faster rate. Thereby cutting into the amount of charge the battery can take and the overall cycle life.

There are a few charts out there that shows that the internal temperature of the cell rises more when using a 1C rate, than when using a .5C rate, which in turn means that more heat or the same heat in a more concentrated area is being produced......which takes you back to all kinds of 'bad' things happening internally which again...cuts into the overall life of the battery.

As was stated above.......the beauty of the LSD batteries is that you should always be able to have enough on hand that you do not 'need' to torture your batteries by electrocuting them at the higher rates....hehe.

A couple areas that I think the higher charge rates really seem to have some merit... 1. reviving older batteries, especially NiCd's and 2. batteries that have constantly been trickle charged and discharged all their lives.

I think that some of my tending towards slower is better stems from the absolutely horrible experiences I have had in the last year/two with the 2500mA and above batteries.


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## Handlobraesing (Dec 18, 2007)

Half of my first set(4 out of 8) of eneloops that I imported before being available to the US are failing. This set has a few dozen cycles on it, then most recently, they were topped off and stored in my camera bag for six months or so. The other half is currently misplaced.

When I put them in my camera that I don't use often, it said "replace battery". When I measured the voltage across the terminals, they were all measuring around healthy ~1.35v, but when I short across the terminals(into a DMM w/ ~0.1ohm IR), I was only getting about 2A, rather than 10A I should be getting.

I put them in the eneloop (that white one) charger and it rejects the batteries. Duracell 30 minute charger rejects each and every one of the four too. I think the internal resistance increased in storage. 

I forced some charge @0.36A using a dumb charger for a few minutes, then I'm discharging at 100mA to nothing and I got as much as 1.7-1.8Ah out of them.


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## SilverFox (Dec 18, 2007)

Hello Handlobraesing,

Interesting...

The Eneloop cells do increase resistance during storage, but that increase is usually reduced when you use the cells. Let us know how your discharge test works out.

Tom


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## letezac (Dec 18, 2007)

Turak said:


> Keep in mind.....
> 
> Probably the absolute WORST charger on the market right now is the Energizer 15 minute charger. Cooks the batteries at a blistering 7.5A. Tested some Energizer 2500's on it.......got between 75-100 cycles before it totally ruined the 8 test batteries. I would be amazed if you can even get 200 cycles out of any battery using that charger. But hey, the battery manufacturers probably kinda like that, means you have to buy more batteries.
> 
> AN UNINFORMED USER IS A BATTERIES BIGGEST ENEMY, HEAT IS SECOND! (hehe)



Rayovac IC3 claim:
I-C3 An Extraordinary Advance in Rechargeables
A rechargeable battery with built-in charging control will provide several significant advantages over other battery technologies: 

Fastest recharging time ever - 15 minutes or less
Longest-lasting rechargeable battery in many devices and lasts up to four times longer than alkaline
Lower-cost chargers - reduced need for expensive smart charging circuitry because the control is in the cell
Batteries can be recharged up to 1,000 times
Safe design - system monitors the charge in each individual battery, eliminating internal cell pressure build-up for safety, speed and reliability.
I have a set and they works absulutely fine.
J.L.
Mx


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## radellaf (Dec 18, 2007)

Which would imply that it's only _past_ full charge that the 3C rate is hurting the Energizers.

I'd be surprised if even perfect EoC detection would prevent 3-4C rates from shortening battery life, but ANY overcharge at that rate is sure going to toast things.

I wonder if the IC3 really was "perfect" sensing. Seems like it would be. Shame the system AFAIK is discontinued. OTOH, the _system_ design was far from perfect. It used flaky resistive-strip sensors to determine whether to fast charge, and with 2 lights for 4 cells, no way to tell that one of your cells was working right, but the other hadn't been sensed and was slow-charging. Also, with the sensor in series with the cell rather than a 3rd contact, charging in non IC3 chargers could cause overcharge via repeated-re-recharging cycles.

I think the charger would -dv/dt detect any cell at high rates, but i believe one CPFer was kicked off or left after posting instructions to cause it to fast-charge other cells and thus touched off a torrent of loud (albeit justified) concern. Now we 15-min charge anything and, eh, maybe the cell doesn't last as long. Hmm, now I wonder what the voltage-plots of the IC3 in 15 min mode with a regular cell would have been like...


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## TorchBoy (Dec 18, 2007)

*Re: Your advice on Eneloop first charge*



Burgess said:


> BTW, what is the NEWEST "date-mfg code" that anyone has *ever seen* on Sanyo Eneloops ?
> 
> Myself, i've never seen *anything* other than 2006.
> 
> Isn't this strange ?


Yes it is rather strange. My Eneloop AAs have had May 2006 and November 2006 dates, and the AAAs April and October 2006 - apparently 11 or 12 months old when I got them. What gives?



SilverFox said:


> The 15 minute chargers ... I don't recommend it for higher capacity cells. My 2500 mAh cells ended up with only about 60% of their initial capacity after 150 cycles.


Don't the high capacity cells last about that long anyway?

Handlobraesing, keep us posted.


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## Handlobraesing (Dec 19, 2007)

TorchBoy said:


> Yes it is rather strange. My Eneloop AAs have had May 2006 and November 2006 dates, and the AAAs April and October 2006 - apparently 11 or 12 months old when I got them. What gives?
> 
> 
> Don't the high capacity cells last about that long anyway?
> ...



alright, so they've been acting very strange. After some 6 months of sitting around open circuit voltage was around 1.4v. All seems dandy, right? Short circuit current 2A , which is 1/5 of what a fully charged NiMH AA usually gives. These cells caused my camera to go into low battery alert mode and it charger would reject it.

Doing a discharge test, it would quickly fall below 0.9v and cut off at 500mA discharge, but they held around 1770mAh at 100mA discharge, holding around 1.02v most of the time. Talk about SERIOUS voltage depression. 

Capacity? *1770mAh to 1860mAh *@ C/20 rate. So yes, they did hold up to the claim of ~90% of charge remaining after 6 months.... Although I put them in the dumb charger, it was only for 5 minutes before the discharge test to see I can get the eneloop charger to accept the cells, so the affect on remaining capacity was negligible. 

Well, I don't know what the deal is with these cells. I think the internal resistance grew MASSIVELY. Using the methods described on Duracell engineering datasheet, I checked them. Take the OCV, then divide by flash short circuit current. 

Even after 100mA * some 20 hours of discharge, these cells are holding OCV of 1.29v. 
So, I crowbar'd across the battery using 1mV/A shunt (much much lower resistance than DMM, so contributing to less error) and I got 3.3A. So the internal resistance of cell is close to 400mohm!

After a full discharge, cells usually won't provide short circuit current for a long time, but these cells continue to provide ~2A into DMM for some time. 

Both the eneloop charger and Duracell 30 minute charger continue to reject these batteries and flash an error code.

I'll charge them again one more time on a 360mA Energizer dumb charger, but if that fails to recover it, I suppose these batteries are bound for trash or SilverFox lab eh?



After 30 minutes of forced charging at 0.36A on the dumb charger, the 300mA eneloop smart charger is no longer rejecting the cells, however the Duracell 30 minute charger continues to reject the cells. Now after an hour or two on the eneloop smart charger, the short circuit current (not into 0.1 ohm DMM, into 0.001 ohm shunt) increased to about 15A. From healthy NiMH cells, I expect 30-50A, so it's still got a case of high internal resistance, but it's recovering. 

The Duracell 30 minute charger is no longer rejecting the cells, but it does concern me that while eneloops hold their coulombic capacity in mAh, the internal resistance shoots up beyond practical use.


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## Burgess (Dec 19, 2007)

Yes, perhaps SilverFox can perform an Autopsy on these cells,
and discover the cause of death. :candle:



Very interesting, indeed.

_


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## Handlobraesing (Dec 20, 2007)

After 3 cycles at 1000mA charge/discharge (I know it's rather high, but it's to reduce the time it takes for testing) the cell resistance have dropped to usable 90 to 145mohm, which yields 10-15A crowbar short circuit current, still 1/2 to 1/3 of what I could get form known good eneloop cells that's sat around for weeks after charging. 

This is an indicator cells will perform poorly under high load conditions. Oh well, eneloop seemed good in theory, but after some cycles, they developed weird symptoms.

Thou shalt not challenge Li-SO2 and CR123A for mission critical applications.


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## TorchBoy (Dec 20, 2007)

*Re: Your advice on Eneloop first charge*



Handlobraesing said:


> ... which yields 10-15A crowbar short circuit current, still 1/2 to 1/3 of what I could get form known good eneloop cells that's sat around for weeks after charging.


I had heard that the short circuit current was about 17A. You're saying it's 30A?


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## gravityz (Dec 20, 2007)

i have a conrad digital charger which has the same features as the maha

charging current can be set independently.

i have noticed that when i charge an eneloop AA battery it gets warm when it is nearly full

i use a 500ma setting which should be prettty low.

so during charging no problems but when it is almost full it gets warm like it is still trying to push 500ma into a full battery
is this normal


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## Handlobraesing (Dec 20, 2007)

*Re: Your advice on Eneloop first charge*



TorchBoy said:


> I had heard that the short circuit current was about 17A. You're saying it's 30A?



As I said, you'll have to use a very low resistance shunt and measure the voltage across the shunt.

If you use a DMM to measure it, the lead resistance is significant enough to totally throw off the result, relative to battery's internal resistance.


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## SilverFox (Dec 20, 2007)

*Re: Your advice on Eneloop first charge*

Hello Gravityz,

It is normal for NiMh cells to heat up at the end of the charge, but you don't want them to get too hot. The difficulty comes from defining what is "too hot." You can do a search and find some other threads where this has been discussed.

The ending cell temperature is dependent on what method the charger uses to terminate the charge and what values it uses. The battery manufacturers recommend charging at a rate that completes the charge in 1 - 2 hours when the charger uses a termination based on -dV or temperature rise. You may find that your cells will remain cooler if you raise your charge rate to 1000 mA.

"Normal" charging is charging at 0.1C for 16 hours. Faster charging requires proper termination. The strongest termination signals occur when charging at 0.5 - 1.0C. Cells still generate heat during charging at these rates, but they should just feel warm at the end of the charge. If you can't comfortably hold the cells in your hand at the end of the charge, you are damaging your cells.

Tom


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## SilverFox (Dec 20, 2007)

*Re: Your advice on Eneloop first charge*

Hello Handlobraesing,

Very interesting...

You may be doing some damage to the cell by using such a low resistance shunt. I have seen a 0.01 ohm shunt is used for this measurement, but nothing lower. I do not use flash amp testing, nor do I recommend it, so I don't have a lot of experience with it. I have run the Eneloop cells through several cycles of 5 amp discharges and have been impressed with their performance.

At any rate, it is also interesting that the cell is trying to recover.

If you are looking for something to do with those cells, I would be happy to take them off of your hands and "play" with them myself.  

Tom


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## Handlobraesing (Dec 21, 2007)

*Re: Your advice on Eneloop first charge*



SilverFox said:


> Hello Handlobraesing,
> 
> Very interesting...
> 
> You may be doing some damage to the cell by using such a low resistance shunt.




It was the method recommended by Energizer engineering datasheet. The shunt is 1.0 x 10^-3 ohms, but I'm sure the foot long 18 AWG lead and contact resistance brings this up close to 5-10 x 10^-3 ohms. I'd say the stress on battery from doing this is equivalent to starting a motor. 

Fluke 87 only needs a mS or so to catch peak voltage, so I only let the flash current very very briefly


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## SilverFox (Dec 21, 2007)

*Re: Your advice on Eneloop first charge*

Hello Handlobraesing,

Interesting, I thought Duracell usually measured impedance using 1kHz AC.

Are your cells continuing to recover?

Tom


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## Handlobraesing (Dec 21, 2007)

*Re: Your advice on Eneloop first charge*



SilverFox said:


> Hello Handlobraesing,
> 
> Interesting, I thought Duracell usually measured impedance using 1kHz AC.
> 
> ...



Energizer is what I meant to say. My bad. Energizer describes both methods.

Anyways, final readings before they're sent in. They were fully charged and haven't been discharged except the very brief flash amp tests. 

(1)1.387v, 4.67A
(2)1.392v, 5.28A
(3)1.423v, 12.2A
(4)1.400v, 9.48A


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## SilverFox (Dec 21, 2007)

*Re: Your advice on Eneloop first charge*

Hello Handlobraesing,

Thanks, I will see what I can do with them...

By the way, if you are referring to this data sheet, the actual value they are using is 0.01 ohms.

Tom


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## Ray_of_Light (Dec 21, 2007)

There are very little info available on the Eneloops, to date. From what I have been able to find out:

1. Eneloops uses nickel oxide at the positive electrode, but the composition of the alloy (and the type of electrolyte) discourage the formation of nickel oxyde with an oxidation status of 3. Nickel metal has oxidation values of 2 and 3, the latter being one of the major player of fast self-discharge of standard Ni-MH cells. Denial of oxydation value 3 decreases the capacity of the cell, from 2500 to a maximum of 1800 mAh, and increases the internal impedance of the cell.
2. Eneloops uses potassium hydroxyde as electrolyte, but at lower concentration (was 30% in standard Ni-MH). Lower concentrations discourage self-discharge, but increases the internal impedance of the cell.
3. Eneloops uses a similar rare-earth alloy at the negative electrode, (which mimickes the behaviour of palladium) in keeping hydrogen mulecules inside its physical sponge-type structure. The new alloy is less prone to release hydrogen by itself. 
This "ability to retain" increases over time. This behaviour greatly reduces self-discharge, but increases internal impedance of the cell.

There is to note that these three parameters have, for long time, been threated randomly from Ni-MH cell manufacturers. They have now been brought "under control" with the Eneloops and their clones.

I would not compare standard Ni-MH and Eneloops. The higher energy of extraction of the alloy at the negative electrode, and its tendency to increase, is very similar to the "passivation effect" present in the lithium thyonil-chloride batteries.
The Eneloops battery is not loosing energy over time, but only the capacity to deliver it quickly. The values are calculated so that with an average current draw of 500 mA it is barely noticeable.

As you may already have noted, three cycles restores the original internal impedance, which theoretically is about the double of the standard Ni-MH cells.
I wouldn't bother with fast charge-discharge cycles of Eneloops or other clones. They are designed to replace alkalines, not high-current NiCd or NiMH, even if they share the same chemistry.

Hope this helps

Anthony


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## Albinoni (Dec 22, 2007)

While on the subject of Eneloops can you overcharge and damage them say for eg if I charge mine overnight will they get hot, damage, explode etc. Or does the charger regulate them and turns off once their charged by cutting of the circuitry.


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## SilverFox (Dec 22, 2007)

Hello Albinoni,

The charger is supposed to shut off when the cell is fully charged and avoid overcharging the cell. Please note that not all chargers are equal in this task.

Low self discharge cells can be overcharged, and when overcharged will suffer damage just like other NiMh cells. Venting and "rapid disassembly" (  ) are possible, but you have to work at it. For example, if you parallel a single cell with a 12 volt lead acid battery and are able to maintain the connection as the cell heats up and vents, you may end up with rapid disassembly of the cell.

Tom


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## Handlobraesing (Dec 23, 2007)

SilverFox said:


> Hello Albinoni,
> 
> The charger is supposed to shut off when the cell is fully charged and avoid overcharging the cell. Please note that not all chargers are equal in this task.
> 
> ...



Do blunt force to top and bottom that causes the bottom to dent a little damage 'em? The ones I sent you have been used in a 4AA flashlight and suffered small dents on the bottom from the light being dropped.


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## SilverFox (Dec 23, 2007)

Hello Handlobraesing,

Yes, blunt force can damage a cell. 

If you are going to drop a light, you might consider dropping it so it lands on its side. That way the force is spread over a larger area... 

With that said, I have dropped plenty of lights and had the cells continue to work in them without problems.

Tom


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## Handlobraesing (Dec 23, 2007)

SilverFox said:


> Hello Handlobraesing,
> 
> Yes, blunt force can damage a cell.
> 
> ...



Usually, when that sort of failure happens, the cell discharge itself quickly and you'll see a decline in capacity. I've not had one cell that would hold 1.35v, but would creep up many folds in internal resistance until these eneloops. Oh well, when VidPro take 'em apart after your test, answer might be found


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## Handlobraesing (Jan 3, 2008)

SF, any observation on those eneloops?


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## SilverFox (Jan 3, 2008)

Hello Handlobraesing,

Now that I have revived them, I suppose you want them back...  

My observations so far...

Cells 1, 2, and 4 have been used, or abused, a lot. They are coming in at lower capacity, but are still good.

Cell 3 is behaving almost like a new cell.

When I first received the cells, cell 2 showed HIGH on the C-9000 when I tried to charge it. I tried a discharge and cells 1, 2, and 4 showed almost no capacity, even though their voltage was up over 1.4 volts.

I hooked them to my CBA and ran a 1 amp discharge on them. They came in at around 1200 mAh, but the voltage was in the 0.5 - 0.9 volt range. A severe case of voltage depression.

I am not sure what you did to these cells, but they were pretty much done.

I ran a Break-In cycle and several charge/discharge cycles on them and now, with a 0.5 amp discharge rate here is where we stand.

1 - 1658 mAh
2 - 1674 mAh
3 - 1841 mAh
4 - 1693 mAh

Since 1600 mAh is 80% of 2000 mAh, these cells are still worth keeping.

Right now I have charged them half full and am letting them sit for a few days to see how they behave.

Compared to the "crap" you sent me, these are now doing pretty good.

Tom


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## Handlobraesing (Jan 3, 2008)

SilverFox said:


> Hello Handlobraesing,
> 
> Now that I have revived them, I suppose you want them back...
> 
> ...



Seems like the cells were behaving the same way as they were when I got them out after months of storage upon arrival. They were behaving the same as your post "revival" after a few cycles too. 

After a few days, I suspect they'll be back to the same conditions again. I'm not sure what causes a cell to fail like this. They were not used in extremely high drain applications and it was only discharged into the ground a few times from the light being left on. 

The charger used was mostly Duracell 30 minute smart-charger.


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## LuxLuthor (Jan 3, 2008)

I don't get warm feelings from what I have read with the fast chargers. All my NiMH do so well with 0.5 to 1 C charging rates.


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## Burgess (Jan 4, 2008)

Yep !


Far as I am concerned, charging my AA NiMH's at 1000 mA is Fast enough !

:thumbsup:
_


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## Albinoni (Mar 19, 2008)

NiOOH said:


> What I do is discharge them to check remaining capacity. Eneloops have a date code, so I am just interested to know what is their remaining capacity. I do this at 0.2C or 400 mA.
> Then I run "Refresh and Analyze" cycle at 1 Amp charging and 400 mA discharging to get their "as new capacity". After that I consider them ready to eneter service.
> As it has been said, the Eneloops appear to be fully formed and do not benefit from this initial cycling. I only do it to get some basic information about them.



When you say 0.2C what do you mean by this ?


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## TorchBoy (Mar 19, 2008)

*Re: Your ADVICE on Eneloop first charge*

"C" is a current equivalent to the capacity in one hour. For an eneloop with a capacity of 2000 mAh, 1C is 2000 mA, and 0.2C will be 400 mA.


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## Albinoni (Mar 19, 2008)

*Re: Your ADVICE on Eneloop first charge*



TorchBoy said:


> "C" is a current equivalent to the capacity in one hour. For an eneloop with a capacity of 2000 mAh, 1C is 2000 mA, and 0.2C will be 400 mA.



Ok how dumb of me I thought C meant degrees celcius:shakehead
Now this starting to get very confusing for me, sorry as I'm new to this.
So C = Current if I'm correct. So if I buy a NiMH batery that is 1800 mAh Milliamps this would mean its 1C would be 1800 mAh, so we could say its default current is 1800 mAh. So above when you got 0.2c=400mA this means you multiplied 2000 by 0.2 (2000mA * 0.2) = 400

Now re this under what circumstances would this formual come handy, eg when I want to charge my Eneloop in my Maha C9000 or Discharge them.

My Maha C9000 is a totally new toy for me and a complete different ball game to my simple Sanyo Eneloop NiMH charger where you just simply plugged it in and away you go. The C9000 is a fully programmamble charger allowing the user to set different settings for this and that, charge rate etc.

For eg at the moment I'm using fully auto mode, just insert the batts and leave them and let the chager sort itself out. But I eventually want to learn is to work out whats the best discharge rate for my Eneloops and the best Charge rate, eg charge at 1.5 mAh/2.0 and discharge at whats best for the batts. So far I'm happy with the Auto leave and set mode but since I've got this charger I would like to learn to use it to its full potential.

Thank you


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## SilverFox (Mar 19, 2008)

*Re: Your ADVICE on Eneloop first charge*

Hello Albinoni,

Grab your calculator and let's see if we can get rid of some of this confusion...

When you turn your flashlight on, it draws current from the battery. Current is measured in Amps (A). Sometimes, the current draw is very low. Rather than writing that the current draw is 0.010 Amps, we do some scaling and multiply it by 1000 and call the result milliAmp (mA). In this case the value would be 10 mA.

A milliAmp is 1/1000 of an Amp. Take your calculator and press 1 and divide it by 1000. You should come up with 0.001.

Now let's look at your battery. It has a labeled capacity that is usually given in mAh. To convert that to Amps, we have to take that number and divide it by 1000. If your battery is labeled 2000 mAh, and we divide it by 1000, we come up with 2 Amp hours.

Ideally, this means that you should be able to run something that draws 2 Amps for a period of 1 hour. Unfortunately, life is not ideal, so we actually end up with a little less than 1 hour of runtime.

So, when you talk about current, you use Amps or milliAmps. When you talk about capacity, we have current over a period of time. This gives us milliAmp hours, or Amp hours.

Now let's move on to charging.

C refers to the batteries capacity in mA or A. 1C for a 2000 mAh battery is 2000 mA. 1/2C, or 0.5C for that same battery would be 2000/2 = 1000 mA. 2C would be 4000 mA. The C rate is used both for charging and discharging.

If your light draws 500 mA, and your battery has a capacity of 2000 mAh, then you would expect a runtime of around 4 hours.

In the same way, if you set your charger to charge at 1000 mA, and charge a 2000 mAh cell with it, you would expect it to take around 2 hours to charge. To figure the charge rate as a C rate we put the charge rate on top and divide it by the battery capacity. In this case 1000/2000 = 0.5C.

When charging, you get the strongest -dV charge termination signal when you charge at rates in the 0.5 - 1.0C range. In order to get a feel for this, I will give you some problems to work on.

If your batteries capacity is 2000 mAh, what would be a 0.5C rate?
With the same battery, what is the 0.1C rate?
OK, how about a 0.2C rate for the same battery?

Now, lets take a look at your new charger. There are standards that the battery manufacturers use to determine the capacity of a battery. The standard charge is charging at 0.1C for 16 hours. The standard discharge is used to measure capacity and the discharge is completed in 5 hours. 1/5 = 0.2, so the discharge rate is 0.2C. Your charger has a Break-In function that does this for you. When you select Break-In, you are then asked to enter in the capacity of the battery you want to charge, and the charger will figure the charge and discharge rates for you and charge the battery at 0.1C for around 16 hours, let it rest for an hour, then discharge it at 0.2C for about 5 hours, then it rests again for an hour and ends up charging again at 0.1C for about 16 hours.

In normal use, you charge at 0.5C. Once or twice a year, it helps your batteries if you take the time to run a Break-In cycle on them.

To finish up the subject of charging, I am going to give you some more problems to work out. You may have batteries of varying capacities, so let's look at those.

If your battery has a capacity of 2600 mAh, what is the 0.5C charging rate?
If you had a 2400 mAh battery, what would the 0.5C rate be?
How about a AAA 800 mAh battery?
Or a AAA 600 mAh battery?

Moving on to discharging, there is no "best" discharging rate. I usually try to figure out what the device I am going to be using the battery in draws, then I do a discharge at around the same current. This will give me an idea of what I can expect for runtime.

That is about it for discharging.

Your charger also has the ability to cycle your cells. Sometimes your batteries will become "sluggish" and loose their "vibrancy" when they have been stored for a long time (to me, a long time is over a month...). A few charge/discharge cycles may help bring them back to near peak performance. 

The cycle mode asks you for both the charge and discharge rates you want to use. The purpose of the cycle mode is to exercise your batteries, so you can charge at 0.5C and also discharge at 0.5C, or the maximum allowed by the charger, and 3 is a good number of cycles to use.

Have fun.

Tom


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## 45/70 (Mar 19, 2008)

Handlobraesing said:


> They were not used in extremely high drain applications and it was only discharged into the ground a few times from the light being left on.


Yeah, I know this post is 2-3 months ago, but wouldn't this damage the cells and possibly cause the problem discussed? I've been more wrong than right lately, so maybe not, but I thought draining a NiMH "into the ground" caused some degree of permanent damage to the cell?

Dave


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