Eneloop Self Discharge study

[Canuke]

They self-discharge slower to be correct. And yes they should last for more cycles, fewer charge cycles is one of the tradeoff's of the higher mAH batteries.

Especially when one factors in the additional charge cycles *necessitated by self-discharge* that the Eneloops won't need.

 

[roadie]

Silverfox Well Done !! :goodjob: :goodjob: :goodjob:

Thank you for yr in-depth study of the eneloop, really open my eyes ....

i will be using the eneloop for my upcoming magmod .....

as its hard to source for high discharge nimh which is "cheap" like eneloop as compare to R/C sub C batteries in Singapore ....

 

[Phaserburn]

Especially when one factors in the additional charge cycles *necessitated by self-discharge* that the Eneloops won't need.

Very good point. I as many cycles are put on a cell because of self-discharge as actual use.

 

[MrAl]

Hello,

I see 1000 cycles on most of the NiMH cells i see on the web.
The wording is 1000 cycles to 80 percent capacity.
If this is really true, these are great batteries!
I have by doubts though, but i wont say anything until i've seen for myself.

BTW, in my quest for the best batteries, best flashlight, best LEDs, i forgot to
take the time to say thanks to Tom for all his hard work with the testing of
the various cells...i know it's not easy because i've done some of it myself and
it is very time consuming and you have to make sure you get everything right or
the results will not be valid, so thanks very much Tom for taking the time to
do this, which benefits all of us who care about our lights and cells.

 

[SilverFox]

Hello Al,

Cycle life is defined as the number of cycles it takes to get to 80% of initial capacity utilizing a standard charge of 0.1 C for 16 hours followed by a 5 hour discharge. All of this is done at standard laboratory temperature conditions.

The Battery Handbook states that NiMh chemistry is good for roughly 500 cycles under these conditions.

Now, if you only do a partial discharge most of the time, your cycle life can exceed 1000 cycles. Duracell did some studies where they charged cells to 85% of full capacity and cycled the middle 60% of the cells capacity. They got excellent cycle life, in the laboratory.

Tom

 

[bp044]

I agree with MrAl's quest to have the best batteries.flashlights and led's.He does not mention a desire the have the best charger. Iwomder if he and others would help me out with a list of their " best "or favorite chargers.Particularly for use with Eneloop's

 

[3rdDerivative]

My results after 6 weeks self-discharge:

Sanyo 2700mha -latest from TD (superlattice alloy EVO) --- 2313
Eneloop AA --- 1782

So 2700 still winning overall at 6 weeks. Hmm. Are these latest 2700mah Sanyo's really that good?

Note: 6 weeks of self-discharge, tested on Maha C9000 at 400ma discharge rate. Storage 72F or lower.

 

[paulr]

A note on capacity: I just acquired a 4-pack of AAA eneloops (thanks to Coppertrail), mfgr date apparently 8/2006. I put one into a 1aaa flashlight (L0P CE) and ran it to exhaustion, then plopped it into my BC900 (initial voltage displayed: 0.86 V) and fully charged it at 200 mA (C/4 nominal). Total charge taken was 850 mAH which I suspect means the actual capacity of this cell is somewhere south of 750 mAH.

I put a second AAA eneloop in the light and used it for a while, I'd have thought maybe to 50% or so. I then put it in the BC900 and the measured voltage was 1.24V which in my experience with HR-3U AA cells has meant the cell is about ready for a recharge. After a couple hours the cell was at 1.55V and somewhat warm. I thought the BC900 should shut down if the voltage got anywhere near that high. I suspect the BC900 missed termination. Anyway I pulled the cell out and I hope it's not damaged. It's in the light right now and seems to be working ok.

 

[Mike abcd]

A note on capacity: I just acquired a 4-pack of AAA eneloops (thanks to Coppertrail), mfgr date apparently 8/2006. I put one into a 1aaa flashlight (L0P CE) and ran it to exhaustion, then plopped it into my BC900 (initial voltage displayed: 0.86 V) and fully charged it at 200 mA (C/4 nominal). Total charge taken was 850 mAH which I suspect means the actual capacity of this cell is somewhere south of 750 mAH.

I put a second AAA eneloop in the light and used it for a while, I'd have thought maybe to 50% or so. I then put it in the BC900 and the measured voltage was 1.24V which in my experience with HR-3U AA cells has meant the cell is about ready for a recharge. After a couple hours the cell was at 1.55V and somewhat warm. I thought the BC900 should shut down if the voltage got anywhere near that high. I suspect the BC900 missed termination. Anyway I pulled the cell out and I hope it's not damaged. It's in the light right now and seems to be working ok.

I've seen AAA cells hit 1.60 V regualrly charging on the BC-900 without missing termination. I doubt your Eneloop missed charge termination although it was probably close to fully charged.

Mike

 

[paulr]

Hmm, interesting, I'm more used to AA's and I didn't realize AAA's acted differently. Thanks.

 

[Mike abcd]

Hmm, interesting, I'm more used to AA's and I didn't realize AAA's acted differently. Thanks.

I don't think they really behave differently given the same C charge rate. It's just easier to charge AAA cells at a higher C rate than AAs on the BC-900 and I regualrly do. The C rate largely determines terminal voltage.

A lot of the cell heating on the BC-900 and other chargers is due to heat from the charger circuitry. The higher the total charge current, the hotter the charger circuitry, the hotter the cells get. I rarely charge 4 AA cells over 700 mA (~.3 C) on the BC-900 because of this but regularly charge AAA cells at .7 C and higher which causes the higher terminal voltage.

Mike

 

[bob_ninja]

3rdDerivative,
Comparison of brand new cells doesn't represent the actual user experience as with usage they get damaged, some more and others less. In particular, if you tested Sanyo 2.7Ah vs Eneloop 2Ah AFTER some real world usage (mixed applications) then you would probably find that higher capacity cells sustained more damage and have a faster SD rate compared to Eneloops. Many reported here drastically accelerated SD rate on Energizers, 2.5Ah after less than 100 cycles. No such reports for Eneloops so far (still early though).

 

[Perfectionist]

To get the best performance from these Eneloop batteries ..... do I need to get the Eneloop charger too ??

 

[paulr]

Regular charger is fine.

 

[3rdDerivative]

3rdDerivative,
...In particular, if you tested Sanyo 2.7Ah vs Eneloop 2Ah AFTER some real world usage (mixed applications) then you would probably find that higher capacity cells sustained more damage and have a faster SD rate compared to Eneloops. Many reported here drastically accelerated SD rate on Energizers, 2.5Ah after less than 100 cycles. No such reports for Eneloops so far (still early though).

My thoughts also. Right now these are pristine cells as are the Eneloops.

 

[3rdDerivative]

Oh, should have added this to my post.

I have a digital wireless outdoor thermometer. Last year I noticed on really cold days I would sometime lose the signal. Thought about using AAA lithium, but need does not justify price. So tried the AAA Eneloops starting around November or late October. Just pulled these out and ran a discharge cycle. Still 650mah+ and no lost signals with -1F low so far.

Very impressed.

 

[SilverFox]

Hello Mike,

I've seen AAA cells hit 1.60 V regualrly charging on the BC-900 without missing termination. I doubt your Eneloop missed charge termination although it was probably close to fully charged.

Mike

[/quote]

Interesting...

I don't see high termination voltages with AAA cells until charging at around 2 C. I have seen high voltages when cells develop higher impedance. It would seem you have some high impedance cells...

That might also explain why your cells heat up so much while charging.

Tom

 

[SilverFox]

Hello Paulr,

If you still know what cell that was that reached 1.55 volts, mark it. It will be interesting to see how it "ages."

Tom

 

[Sub_Umbra]

Wow, thanks Tom.

 

[Raptor#]

Thanks Tom!

I sure would like to see a heads-up comparision between the Eneloops and Rayovac Hybrids. Hopefully, they will be close to the same, since I loaded up with Hybrids for $3.87 per package of 4-AAs and I used up all 10 of my $5.00 off coupons.

Yupp. There are a few other long-lasting NiMh's now, wich followed shortly after the eneloops... "Ready2Use" from Varta, "maxE" from Ansmann.. and at www.swissbatteries.com they claim 2500mAh at 1,2-1,4V.