Eneloop AAA self-discharge study

[etc]

Charger was Vanson "smart" charger.

4-12-07:

Fresh off the charger, 1.46V

7-14-07 (3 months 2 days later): 1.32V

I wonder how much Maha Powerex 2700 mAh would discharge, as it's my favorite cell.

 

[Burgess]

Thank you for the Eneloop info.


Yep, i wonder the same thing.


Why not test a couple of 'em,
and report back here in 3 months.



(gonna' be eatin' lotsa' popcorn whilst i wait)

-

 

[barkingmad]

Charger was Vanson "smart" charger.

4-12-07:

Fresh off the charger, 1.46V

7-14-07 (3 months 2 days later): 1.32V

I wonder how much Maha Powerex 2700 mAh would discharge, as it's my favorite cell.

Not sure just testing the voltage is really accurate enough - would be better to do a propter discharge at about 0.1/0.2C?

 

[Curious_character]

Sorry, the terminal voltage of a NiMH cell tells you nothing about the amount of charge remaining -- unless it's around 1.1 volt or below at no load in which case you know it's nearly fully discharged.

The only way to tell the state of charge is to discharge it at a known current and measure the time it takes.

Open circuit terminal voltage can be used to approximate the state of charge of Li-ion and lead acid batteries, but not alkaline, NiCd, or NiMH.

c_c

 

[cave dave]

Yup. Open terminal voltage is not a good indicator of remaining charge.

Here is a discharge test on 4 AA Eneloops straight from the package with a manufacture date of 0609 (sept 2006)

Discharge at 500mA
Avg capacity: 1470mAh

As I understand it Eneloops only have a 85% charge put into them at manufacture. Then it lost almost 14% from being in storage for 10 months.

 

[barkingmad]

Yup. Open terminal voltage is not a good indicator of remaining charge.

Here is a discharge test on 4 AA Eneloops straight from the package with a manufacture date of 0609 (sept 2006)

Discharge at 500mA
Avg capacity: 1470mAh

As I understand it Eneloops only have a 85% charge put into them at manufacture. Then it lost almost 14% from being in storage for 10 months.

I heard it was actully 75% from manufacure which would mean only 4% loss which is probably more accurate.

Think I saw Sanyo saying 10% loss in the first 6 months and 5% for the following 6 months - i.e. 15% in total in a year - but that is also from a full charge!

 

[PlayboyJoeShmoe]

I don't have a smart enough charger to do capacity testing.

So I check voltage a lot. It doesn't absolutely mean the battery is ok if it shows 1.3 or more.... but generally speaking it's close enough.

I get a great deal of info when I use two AA in my Garmin GPSr.

So far Hybrid and Eneloop NimH run it just fine at a starting V of 1.3x

Some Rayovac 1800 with 1.3x ran it ok but showed less time remaining than the Hybrids and Eneloops.

When 2500 NimH are good, they will run the GPSr for nearly 12 hours. But it's getting HARD to get two 2500s paired up!

 

[paulr]

Open circuit voltage does seem to be somewhat correlated with charge state, though it's not anything like an accurate measurement.

 

[lyyyghtmaster]

Re NiMH:
I personally use the open circuit voltage of LSD cells to tell me whether I've remembered to recharge them or not.
I wonder if OCV could be more closely correlated with charge state if all the cells being compared are similar, i.e. same age, usage, charging, etc. Then you could probably draw up a curve that would tell you, approximately of course, how much charge a given cell would likely have based on its OC voltage. But you'd have to recalibrate as the cells age, etc. And partial recharging before measuring voltage, or measuring too soon after discharge, would skew the results.

Re Alkaline:
I'm not an expert on alkaline by any means, but I have always heard that OCV is an acceptably good indicator of remaining capacity for this chemistry if you wait awhile after any discharge. I employ it quite effectively to screen used cells for remaining capacity for wireless microphones.

 

[PlayboyJoeShmoe]

I fully intend not to sweat it for a good while as I have enough LSD (mix of Hybrid and Eneloop) to run my GPSr for two 5 day work weeks and will probably get another weeks worth pretty soon.

As for lights, my main ones that get used have either a 123 Primary, an AA or two Alk or NimH or 2C Alks.

 

[europium]

I bought a MH-C9000 charger/analyzer from TD, along with some 4-packs of AAA Enelooop NiMH batteries. The manufacture date on the rear of the packages was 2006-04, or April of 2006.

I did not test open voltage (since I don't have a voltmeter), but using the ZTS MBT-1 (new version) I got mostly 60% and sometimes 80% and once 40% tested capacity with the 4 AAA cells in repeated MBT-1 testing.

I then ran a discharge at 300mA on the C9000, and got between 514mAh and 544mAh in about 2 hours on each cell, hence between 60% and 70% of actual expected capacity after 15 months.

But of course I don't know what was the initial charge when the batteries were packaged.

Eu

 

[barkingmad]

I bought a MH-C9000 charger/analyzer from TD, along with some 4-packs of AAA Enelooop NiMH batteries. The manufacture date on the rear of the packages was 2006-04, or April of 2006.

I did not test open voltage (since I don't have a voltmeter), but using the ZTS MBT-1 (new version) I got mostly 60% and sometimes 80% and once 40% tested capacity with the 4 AAA cells in repeated MBT-1 testing.

I then ran a discharge at 300mA on the C9000, and got between 514mAh and 544mAh in about 2 hours on each cell, hence between 60% and 70% of actual expected capacity after 15 months.

But of course I don't know what was the initial charge when the batteries were packaged.

Eu

Pretty sure Sanyo only say they are 70-75% charged when shipped anyway. Only real way to test would be to charge them fully / discharge a few times - then charge them full and store for a year then compare.

Sanyo state 10% in the first 6 months and 5% more for the next 6 months - i.e. 15% over a year and probably around 25% over 2 years.

 

[PlayboyJoeShmoe]

A pair of Hybrid (Rayovac LSD) AAs that were in a light that didn't get much use for at least a month and never got charged since being in the light ran my GPSr for about 9 hours and 20 minutes today and STILL had some to give.

Maybe Eneloops are even better, but don't sneeze at Hybrids!