How bad for modern NiMH AAs to go into polarity reversal?

My experience with modern high capacity AAs sporting as much mAh (2700mAh) as a lower capacity sub-C cell is that they're not as resilient as older NiMH and NiCds

My oldest NiMH are Energizer 1200mAh.. I think they're circa 2000 and even though they've been mostly abandoned, leaked a little and discharged to 0.00v, after a few cycles, they're still giving 1,000 to 1,100 mAh even at 1A load.

Same with industrial NiCds I have that must be over 10 years old, but still have low internal resistance and 2.3Ah capacity

In comparison the high volumetric density NiMH cells lose capacity after not that many cycles even if they're taken care of well... and it seems like a few mishaps (discharging to polarity reversal)

So, just how damaging is accidentally leaving a light on and causing a cell to go into polarity reversal?

Would you say it's like accidentally rubbing against some brush along the side of road adding to wear and tear type scratches or is it more along the line of backing into a pole?

The obvious solution is to not use "delicate" high capacity cells. Eneloops cells for example are not only low self discharge, but extremely robust compared to other NiMH brands.

Ragiska said:

The obvious solution is to not use "delicate" high capacity cells. Eneloops cells for example are not only low self discharge, but extremely robust compared to other NiMH brands.

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Duracell still ships 1700 and 1800mAh NiMH cells in their value chargers. Try to find them by themselves though. You don't see them on shelves. You'll only find 2500mAhs.

The Duracell precharged (some lots are eneloop, but not all) looks promising but they're rather costly.

So, just how damaging is accidentally leaving a light on and causing a cell to go into polarity reversal?

Would you say it's like accidentally rubbing against some brush along the side of road adding to wear and tear type scratches or is it more along the line of backing into a pole?

backing into a pole it depends on how much it was hit by this reversal, and how the device itself reacts when the battery is low.

when the cells are out of "balance" the reverse charge hits for a lot longer time, AND this means that cells that are Self_discharging at offset rates, can cause the problem to be worse, as the reverse happens longer.
THEN after the one cell gets "backed into a pole" it becomes further offset balanced, because that cell becomes worse again.

some devices dont cause a reverse as badly, take a 2 cell unit that stops operating at about 1V, it cant do much damage.
i think the worst probably comes from stuff like 10-12 in series, and they are poorly balanced.
a way to solve some of that is to slow charge top off the batts while in the unit, that way balance is maintained, if they can all at least start neer the same capacity, exaustion of a single cell in the series is less likly to occur. when they have SAT around getting out of balance via self-discharge, then the balance is going to be way off.

the LSDs seem to stay closer to the same capacity (at least when newer) and therfore balanced, even over time. same thing was true for the older 1300-2000ma type AA cells, they didnt have a lot of total capacity, but they were about AT the same capacity (balanced) when discharged.

When they were balanced via the self discharge and total capacity, they seemed to last longer and do better. When they are out of balance, it just goes downhill fast, because the damage furthers the out of balance and self-discharge.

so when you say "modern" using the lower capacity, similar capacity even over time, LSD cells, the balance is maintained "better" and the damage itself is less, because of the balance itself. Even if they would both suffer greatly from the reverse charge, the lower capacity LSD would not GET as much reverse charge, so it doesnt go downhill logrythmaticaly as fast.