At 01:50 PM 9/29/2003 -0400, Tim Hart wrote:
>The other day I read that charging NiMH in 60 minutes might harm the
>batteries.  My 1800 ma/h AA batteries do in fact get quite hot during the
>charging.  I leave the lid off just for cooling.

Something's very wrong. They shouldn't get warmer than about 120F, some
even lower. The cells I'm working with now, charge (end of high rate
charge) in 60 minutes, and don't get above 104F, in an 80F ambient.
Sounds like maybe you have them in a Nicad charger.


>   The article recommended 4 hour charging when you had the time and 60 or
> 90 minute chargers when you didn't :)

No. NIMH ideally charges in 60 minutes.  Outside that, in either direction,
end of charge gets harder and harder to see.
30 minutes is pushing it, but workable.

>Anyway the other day I saw a charger from Energizer that claimed to work
>in 30 minutes!  That sounds like a ploy to destroy batteries and force the
>consumer to buy more NiMH batteries or maybe even give up and go back to
>disposables!  A 2000 ma AA would be getting around 4 amps to charge in 30
>minutes....that seems quite excessive!

There's a lot of variation between NIMH cells, of the same capacity.
Don't make the mistake of thinking NIMH = NIMH, except in very broad terms.

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