Eneloop Self Discharge study

[Gazoo]

Well I have an update too. I had 4 eneloop AA's that have been sitting around and I needed them also. These were manufactured in Aug 2006. I don't know the exact date I tested them but it was about a month ago. Testing was done with the Maha Wizard charger firmware revision 0G0C01.

The capacity of the batteries follow:

Battery 1: 1380
Battery 2: 1386
Battery 3: 1344
Battery 4: 1398

All batteries were discharged at 500ma and were a fresh set out of the package when I tested them. Not too shabby considering they had been sitting in the package for all that time.

 

[windstrings]

Has anyone considered these yet? 2300mah "Tenergy Pre-charged RTU NiMH AA 2300mah Rechargeable Batteries"

85% residual capacity after 1 year of storage and 70% residual capacity after 2 years of storage

The reviews aren't so hot on them.... has anyone found anything better than the eneloops or the Eneloop/Imedion's yet?

 

[windstrings]

Another question...... has anyone determined how bad it hurts shelf life when leaving these batteries in a hot car inside a device on a regular basis?

 

[UnknownVT]

Another question...... has anyone determined how bad it hurts shelf life when leaving these batteries in a hot car inside a device on a regular basis?

Eneloops Left In Car For 1 Year - Results

 

[Radiophile]

This thread is referenced by the California Integrated Waste Management Board as Technical Information about Rechargeable Batteries by a staff person who is an avid user of rechargeable batteries:

http://www.ciwmb.ca.gov/WPW/Power/RechBattInfo.htm

:thumbsup:

 

[windstrings]

I bought some Imedion's, just take note they are slightly bigger in diameter than regular AA's.

They fit very tight in a light I have that works fine with eneloops or duracell lsds.

The difference is almost not noticeable....

 

[samgab]

Excellent study there Silverfox, thanks. I know it was first posted a long time ago now, but I wanted to bookmark it. Cheers! I wonder how the eneloops tested in your study here would compare side-by-side with the newer improved version eneloops? I wonder if they discharge similarly at 2A, 3A, 4A, etc; and if there is any improvement there, or if the improvement is just in the self-discharge rates and the number of claimed cycles per cell lifespan... Some of the new AA devices have pretty high current when the voltage starts to dwindle. I also found Anders' graph interesting, comparing the eneloops to the Imedion cells at higher discharge rates. The eneloops really shine there.

 

[pobox1475]

When I first saw the new and improved AA''s I thought MUST HAVE. Then luckily quickly realized that additional 500 recharges over the original 1000 is not reason for me to spend moola. With an ample supply on hand and not using daily mine should last years anyway. Do wonder if there are any other advantages beyond the additional 50% charging cycles?

 

[Wrend]

http://www.eneloop.info/home/the-new-improved-eneloop.html

 

[mattchase]

Rise from the dead, old thread...

I just got caught up on this thread and saw Windstrings question about leaving batteries in the car (is 2 years too long to wait for a reply?). I haven't done any more "quasi-scientific" tests but I have continued doing many real world tests. Since that time I've continued to use those same Eneloops in a couple of flashlights that stay in my car at all times, and every time I have needed to use one of those lights they have worked perfectly. I know I've charged them a few times after using one of the lights, but literally only a few times, in 4 years of being left in my car. I haven't had any of them leak or explode, and I've only had 1 battery fail completely so far from the original group of 18 that I bought in 2007! Though I also had 6 of those original 18 stolen a few years ago (along with a sweet modified Mag ) so I can't say if those 6 still work or not (I'm sure they do...assuming the thief figured out how to charge them). But of the ones I have remaining, excluding the one that failed, the rest are still in service.

I'm sure by now many others have done these same real world tests and Eneloops have been out long enough that everyone knows how great they (and other LSD) batteries are. Just thought I would share that they still work well after about 4 years of being left in my car - still in the Texas heat, still no covered parking.

 

[Kestrel]

I've got four unopened NIP Eneloop AAA's mfg 5 years ago. As I'm a rather patient person, I think I can wait for another five years before sending them to SilverFox for 10-year testing, LOL. Plus I have a pair of NIP AA 'Shnoopaloops' (remember that closeout? ) from 2008, so it would be cool to test those after they hit their 5-year mark.

 

[MagPap]

Hi there:

I'm new in CPF :wave: , and I would like to make a question regarding eneloops. I have search it in the board but not found an specific response, so I post it here.

I have read one of advantages of LiOn batteries over NiMh are their low rate of discharge. How it compares to eneloops? Which are better in this field?

 

[SilverFox]

Hello MagPap,

Welcome to CPF.

I believe Li-Ion cells still have the advantage, but the low self discharge rate of the Eneloop and other cells has closed this gap a lot.

Tom

 

[Wrend]

I'm not sure if that's the case or not. I haven't seen much in the way of actual independent numbers regarding Li-ion type self discharge rates. Some of the advertised rates of LiFePO4 cells/packs from vendors I've seen are listed as having several times the average self discharge rate that Eneloops have and they advertise it as having good low self discharge performance, for example.

According to Wikipedia, average self discharge rate of Li-ion cells is about 5% to 10% per month or about 8% at 21 degrees Celsius per month. The current "1500" cycle Eneloops are supposed to hold about 75% of a full charge after 3 years. This at least indicates that Eneloops have roughly 10 times better self discharge performance on average after 3 years.

Either way, it's so low with Eneloops that for all but very niche applications (not really any I can even think of off hand) it isn't an issue.

 

[samgab]

I'm currently reading the book "Batteries in a Portable World: A Handbook on Rechargeeable Batteries for Non-Engineers" which contains a lot of useful info.
It seems Li-Ion self-discharges at sometimes as low as 2-3% per month, depending on the specific chemistry (eg: LiFePo4 is quite a bit higher).
Standard NiMh cells are as high as 30% per month rate of self-discharge.
eneloops are as low as 0.5%-2% per month or less (the new ones lose 10% in the first 6 Months, then another 5% in the following 6 Months, then another 5% in the following 12 Months, and another 5% in the next 12 Months and so on - http://www.eneloop.info/home/performance-details/self-discharge.html ).

So eneloops and li-ions are nearly on par in terms of rate of self discharge.
See also http://en.wikipedia.org/wiki/Loss_of_charge although it would be better if they quoted more sources for the figures they quote.

 

[Wrend]

So eneloops and li-ions are nearly on par in terms of rate of self discharge.

I don't follow. According to the info you posted, it looks like in a worst case scenario for Eneloops they'd be on par with Li-ion cells, but typically and on average they'd be several times better.

 

[samgab]

I don't follow. According to the info you posted, it looks like in a worst case scenario for Eneloops they'd be on par with Li-ion cells, but typically and on average they'd be several times better.

Without getting into the nitty gritty... No, they aren't the same, eneloops are a little bit better, from what I've read. But there are so many variables; how old, how many cycles, what device are they in, what temperature are they stored at, what state of charge were they to begin with, vampire discharge from the electronic protection device often attached to the li-ion if any... and the self-discharge curves aren't linear, they start out steeper and level out somewhat... It can't be stated as a simple "2%" and that's it. So in the bigger picture, yeah, they're NEARLY on par... Not exactly the same.
But it's all a matter of context. I realise you like to be precise, having read your posts about how you finely balance your eneloops, so no, from your point of view, they aren't nearly on par. For most people's purposes, I'd say they are pretty close for self-discharge rates...
But eneloops are the best (lowest) rate of self-discharge I've seen yet for a secondary cell of any chemistry. Especially the yet-to-be-released 1800 cycle version.

 

[Wrend]

Thanks for the clarification.

Yes, I agree that what's important to most people is that when they go to use a battery powered device that it still works even though it's been a while since they last used it or charged the cells in it.

Now if I could just get a cell phone that runs on AAs. (The Li-ion cell in my phone definitely isn't up to the specs talked about here any more).

 

[MagPap]

Wow. Thanks for the useful info!!! lovecpf

In resume, since there is not a great difference between Lions and eneloops in LSD rate (altough the latter are somewhat better), I asume is safe to say that LSD rate won´t be the first factor to choose between the two (in a flashlight that can use both, of course..)

 

[led2011]

This is very interesting and awesome. Thanks for all your hard work.
Would you offer me some similar graph about Eneloop 18650 Li-ion rechargeable battery, if you have been interested in it.