Enloop AA Degraded?

I put two of my AA eneloops in my new C4-12 charger. Both charge to about 900mA from a specified 6& on the display. These would be 1900mA cells. Looks like a capacity loss. There have not been used much and were in a low current device for at least 2 years.

Does that charger have a discharge then charge cycle? If so, that would give you a better idea of the cell capacity.

--flatline

Well if everything is functioning correctly, batteries and charger. Your results would just indicate that the batteries were at about 50% capacity when you recharged them. Do you have something capable of doing a discharge test? That's what you need to test capacity much more accurately.



Frank

This new one doesn't appear to have analysis. I had a 328 charger which did but gave it to my son. I may get it back for some testing.

tripplec said:

I put two of my AA eneloops in my new C4-12 charger. Both charge to about 900mA from a specified 6& on the display. These would be 1900mA cells. Looks like a capacity loss. There have not been used much and were in a low current device for at least 2 years.

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Did you get the c4upgrade version?

Anway how much resistance are you getting on those cells?

This is a common mistake many people make.
What happens if you put the same batteries in the charger again? You'll only get 100mAh.
Does that mean the batteries are completely dead, since they should be 1900mAh. Nope.
You can not measure capacity by charging, especially if they aren't empty.
You can only measure capacity by discharging a fully charged battery.

Please have a look here to learn more about charging eneloops. Especially the 3rd question. https://eneloop101.com/charge/

I hope that helps.

I'll add that while some chargers do give "charge capacity", they tend to be very bad at it. Not only because "charge capacity" is not equal to the real "discharge capacity", but for some reason they just don't seem to measure it as accurately. At least, for some chargers.

They do seem to measure discharge capacity much better, though they might still be off a few percent.

If a AA Eneloop really only has 900mAh capacity in it, that cell would perform very poorly (for reasons like super-high IR). So, you'd know it, without needing to test it.

Yes, I realize most of this. Just asking and it is the newer build "C4-12" not the C4.

I'll put them in my light and run them there for a while.

Well I finally ran the white eneloops AA down in my flashlight where it got so dim during normal use.

Recharged them in this C4-12 and final mA showed almost 1800mAH in both of them. I had a dead Ladda 1000 AA which came to ~800mAH much further off the spec. It was run down in a computer mouse so its very low drain.

I ran down a pair of AAA the other day.

Charge them up and notice at the start impedance >800 MOhms on both finishing at ~ 270 MOhms. Also charge capacity at ~ 550mAH on both. I believe 900 is the rating but either way its quite low. I was used in a low drain current device.

tripplec said:

Well I finally ran the white eneloops AA down in my flashlight where it got so dim during normal use.

Recharged them in this C4-12 and final mA showed almost 1800mAH in both of them. I had a dead Ladda 1000 AA which came to ~800mAH much further off the spec. It was run down in a computer mouse so its very low drain.

Click to expand...

and this

tripplec said:

I ran down a pair of AAA the other day.

Charge them up and notice at the start impedance >800 MOhms on both finishing at ~ 270 MOhms. Also charge capacity at ~ 550mAH on both. I believe 900 is the rating but either way its quite low. I was used in a low drain current device.

Click to expand...

You should avoid discharging completely these NiMH batteries. I have done in the past such tests and all resulted in damaging the cells and the internal resistance got to the roof within a few months of doing these tests. As soon as you notice the smallest dim they should be recharged. If you want to measure capacity, invest in an analysing charger that does a discharge to 0.9V or has a function dedicated to measuring capacity via discharge; your approach will ruin your batteries.

On the charger I noticed it started charging the AAA at 1V or a hair above 1.1V
As with the AA previously indicated this charger did display capacity close enough to spec's. I do have an analzing charger but stopped using it as it overheats the batteries. I gave it to my son who needed to do discharge/recharge cycle on some of his eneloop cell which got weak. He uses them in flashlights. "Quark Pro"

tripplec said:

On the charger I noticed it started charging the AAA at 1V or a hair above 1.1V

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That's what I mean, you talk about Open Circuit Voltage (OCV) and you have this low value during charge, I talk about 0.9V under load discharging as a cut-off point. If you have OCV voltage at 1-1.1V the battery already has been over-discharged (1.2V OCV is considered empty). This ruins the batteries. What I do so not to complicate things e.g. for my mouse I use 800mAh AA NiMH and I make a habit to change batteries every 1 month regardless if they have been used up. Normally the battery lasts 2+ months in there with typical use so I have plenty to avoid draining the battery down. Unfortunately, I cannot use the "battery low" indicator of the mouse because it lights up when the voltage is below 1V (designed for alkaline batteries) and if I wait for that light the battery is already over-discharged. Similarly for any other device, i.e. flashlights. If you take care of your batteries, they will last you a long time, over-discharging is a great enemy of longevity.