NiMh AA self discharge comparison

[BatteryCharger]

I was just doing this test for myself but I thought you guys would be interested in the results. I have several different brands of new NiMh AA batteries that I charged 30 days ago. First they got 5 cycles to break them in. Now I am using my BC700 to test their capacity @ 350ma. They have been sitting here on my desk at about 70 degrees for the last 30 days.

Test is not finished, I can only do 4 batteries a day, but so far...

Duracell 2450, 4 samples:
Starting voltage: 1.29
Starting capacity: 2.45Ah +/-
Capacity after 30 days: 1862mAh, 1823mAh, 1783mAh, 1843mAh.

Energizer 2300, 4 samples:
Starting voltage: 1.31
Starting capacity: 2.43 to 2.50Ah
Capacity after 30 days: 2158mAh, 2150mAh, 2162mAh, 2155mAh.

Energizer 2450, 4 samples:
Starting voltage: 1.28
Starting capacity 2.50Ah +/-
Capacity after 30 days: 1265mAh, 2120mAh, 1318mAh, 2160mAh.
I demand a rematch! These resulsts also correspond with mismatching date codes. New test in progress.

Duracell 2650, 4 samples:
Starting voltage: 1.15
Starting capacity: 2.60Ah +/-
Capacity after 30 days: 169mAh, 200mAh, 6(six)mAh, 50(fifty)mAh
*cough*
Ouch. I'm testing a larger sample of these.

Duraloops currently on the tester. I will update this as information comes in...

 

[adam83]

Wow! 25% gone in a month from new cells? I almost forgot how bad standard NiMh self discharged. Im very curious about the energizers too. The last ones I had lost 25% between breakfast and dinner time. :shakehead I'm looking forward to the results

 

[BatteryCharger]

A surprise from the Energizer 2300's...exactly what I wanted to do this test for. :thumbsup:

 

[fishinfool]

A surprise from the Energizer 2300's...exactly what I wanted to do this test for. :thumbsup:

I've been doing my own self-discharge test on about 14 different AA and AAA batts and the Energizer AA 2300's are actually doing pretty good. They are still at 100% (using zts mbt-1) after 14 weeks now. The Energizer AAA 850's on the other hand dropped to 80% after 6 weeks and is down to 60% after 10 weeks.

My Duracell AA 2450's are even worse and dropped to 80% after only 3 weeks and are down to 60% after 8 weeks. The Duracell AAA 1000's (china black top) are just as bad as the 2450's. The Duracell AA 2000's (china black top) lasted 10 weeks before dropping down to 80%.

 

[Battery Guy]

I've been doing my own self-discharge test on about 14 different AA and AAA batts and the Energizer AA 2300's are actually doing pretty good. They are still at 100% (using zts mbt-1) after 14 weeks now.

Your comment suggests that you measured no self-discharge of the AA 2300 cells over 14 weeks. Did I read that correctly? Can you confirm, because 100% at 14 weeks is a bit better than "pretty good"!

Cheers,
BG

 

[fishinfool]

Your comment suggests that you measured no self-discharge of the AA 2300 cells over 14 weeks. Did I read that correctly? Can you confirm, because 100% at 14 weeks is a bit better than "pretty good"!

Cheers,
BG

I just checked my speadsheet and I started the self-discharge test on the Energizer 2300's on April 14, 2010 so it's actually at 15 weeks now. I also, just now, checked them with my ZTS MBT-1 and they are still at 100% so I guess they are a bit better than pretty good. 😀 All the batts I do a self-discharge test on have been fully discharged first then run through a break-in cycle with the Maha C9000.

My other batts that are still at 100% after around 15 weeks are the eneloops and duraloops of course, powerex 2700's and the Rayovac Platinum 2100's. I just bought a bunch of eneloop tones and costco tones and will also start my own self-discharge test on them as soon as I'm done breaking them in.

 

[BatteryCharger]

Test is not over, but we already have a clear looser. Somehow I mistakenly got capacitors disguised as AA batteries. :ironic:

 

[Lynx_Arc]

The duracell 2650s must be cousins to the infamous energizer 2500s. I have some older energizer 2300s and have to charge them every 3-6 months but within 2-4 months they still have at least 50% charge left in them. I used them heavily during a 2007 ice storm here that left us without power for 4.5 days. If they hadn't come out with LSD nimh cells I would probably buy the 2300s again.

 

[fishinfool]

These energizer 2300's are doing pretty good so far but it's only been 15 weeks.
Well see how they hold up over a longer period of time.

 

[Battery Guy]

I also, just now, checked them with my ZTS MBT-1 and they are still at 100%

Are you measuring capacity or voltage? I could be wrong, but it sounds like you are measuring the voltage.

Cheers,
BG

 

[Egsise]

Capacity can't be tested without discharging the cells, so it's just a voltage test.

 

[Battery Guy]

Capacity can't be tested without discharging the cells, so it's just a voltage test.

Ok, that is what I thought.

Most self-discharge tests are performed by measuring capacity lost as a function of storage time. I just wanted to clarify that we are talking about voltage here, and not capacity.

Thanks, and Cheers!

BG

 

[45/70]

Capacity can't be tested without discharging the cells, so it's just a voltage test.

Actually, the ZTS tests the cell's voltage under load, so it's a bit more sophisticated than checking voltage alone. While the ZTS is considered one of the best of this type tester, none of these testers are really very accurate, especially with NiMH cells. They are better suited to testing the various primary cell chemistries.

Dave

 

[fishinfool]

Here's what I read on the ZTSinc.com site:

"ZTS Multi-Battery Testers provide a fully automatic pulse load test to determine state of charge (SOC) or state of power. The pulse load creates real power demand and measures battery performance under load, not just voltage or internal resistance."


Another thing I might do is when a battery gets down to say 40-60%, I will do a full discharge (using the C9000) on those specific batts and see how much capacity(mAh) is left.

 

[Battery Guy]

Here's what I read on the ZTSinc.com site:

"ZTS Multi-Battery Testers provide a fully automatic pulse load test to determine state of charge (SOC) or state of power. The pulse load creates real power demand and measures battery performance under load, not just voltage or internal resistance."


Another thing I might do is when a battery gets down to say 40-60%, I will do a full discharge (using the C9000) on those specific batts and see how much capacity(mAh) is left.

It might be possible to calibrate the ZTS: make a measurement on a fully charged cell, discharge the cell 10% and let it rest for an hour, remeasure with the ZTS, discharge another 10% and repeat. Try this on at least one cell and see how close the ZTS is.

I have to admit that I have my doubts that the ZTS will provide accurate SOC values for a NiMH cell, but I would love to be wrong about that. And I would also love to see the results of a calibration test.

Cheers,
BG

 

[fishinfool]

It might be possible to calibrate the ZTS: make a measurement on a fully charged cell, discharge the cell 10% and let it rest for an hour, remeasure with the ZTS, discharge another 10% and repeat. Try this on at least one cell and see how close the ZTS is.

I have to admit that I have my doubts that the ZTS will provide accurate SOC values for a NiMH cell, but I would love to be wrong about that. And I would also love to see the results of a calibration test.

Cheers,
BG

Ok, I can try that on one or more of my new eneloop tones that are at the end of a break-in cycle which should be done in about 4-5 hours. I will discharge a couple tones 20% instead of 10% since the zts bt-1 shows percentages in increments of 20% and do the rest of what you suggested above.

 

[Lynx_Arc]

The problem with using the same algorithm to test nimh batteries is the batteries themselves differ in their internal resistance and voltage output which both throw off tests. A battery with lower internal resistance and higher voltage would seem to have more capacity.

 

[Egsise]

Yeah because different brand and condition NiMH cells have different voltages under load, the test is just a voltage test.