Why Are So Many Of My AAA Eneloops Dieing?

[Ziemas]

I've recently been doing a break-in on all my AA and AAA batteries on my Maha C-9000, and I've found that a lot of my AAA Eneloops (9 in all) have a capacity of around 650mah, even after two break-in cycles.

These are the first batch that I bought, around two and a half years ago, if memory serves me correct. They have only been charged on the Maha (never over 1C) and I know of only three that have ever been run down totally.

What would be the cause of such degradation? Also, the newer cells that I have all are fine.

Thanks for the help.

Z.

 

[kaptain_zero]

It could simply be that your Maha charger isn't fully charging them, though it should when you do a break in. I find that when I do a refresh/analyze with my Maha, it's generally a little less capacity than when I charge the same cells in my Titanium charger and then measure them in the Maha 9000. If the cells still work ok, I wouldn't worry about it. I rarely drain my batteries to the bottom anyway... only when I can't avoid it. Gently refreshing a rechargeable and especially a LiIon is the way to go.

Regards

Christian

 

[Mr Happy]

I suspect those AAA cells have not really lost 150 mAh of capacity, more likely they are showing the effects of age by developing a higher internal resistance. This does happen to NiMH cells over time as the electrode materials suffer irreversible chemical changes. The C9000 uses a pulsed 1000 mA discharge current and this tends to pull the voltage of AAA cells down quite steeply making them reach the 0.9 V cut off voltage rather sooner than a continuous low current discharge would do.

You could get a measure of the internal resistance from the impedance check voltage shown by the C9000 at the beginning of a charge. When you insert a discharged cell and start a charging program, what voltage do you typically see for these cells?

For comparison with your Eneloops I have some Rayovac Hybrid AAA cells that have never recorded more than 650 mAh on the break-in cycle even when new. Eneloops are one of the few kinds of AAA cell that I have actually seen measure 800 mAh on the C9000 at all.

If one or two break-in cycles is not producing any improvement I wouldn't do any more. It will just wear the cells unnecessarily.

 

[tandem]

Just want to add that in addition to Eneloop/true Duraloop AAA's typically ringing in at 800maH rated capacity without much initial effort out of the package, I've also found Imedion AAA 800maH have been likewise very consistent. Last batch of 16 I broke in every single one reported > 800maH after one discharge/break in/discharge program.