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Subject: Re: to weak batteries - cant even charge... ;-(
From: Linus Nielsen Feltzing (linus_at_haxx.se)
Date: 2004-09-18


VanBaren, Gerald (AGRE) wrote:
> IMHO (and everybody has different opinions on this topic), you are
> being too cautious. You can see the charging current vs. charging
> adapter voltage in:
> http://rockbox.haxx.se/twiki/bin/view/Main/BatteryFAQ NiCd battery
> manufactures univerally (at least in my limited universe) list 1/10
> AH rating of the battery to be the safe continuous charge level. For
> 1800mAH batteries (supplied by Archos), that would be 180mA which is
> approximately what a 9v adapter (supplied by Archos) would provide.
> This probably is no coincidence.

First of all, the batteries supplied by Archos are 1500mAh, which would
give a charging rate of about C/8 with the standard adapter according to
the FAQ. Secondly, if you, like many others, use a regulated 12V supply
to charge, you will have a charging current of 350mA, which is roughly C/4.

> What this means to me is that I can charge at full tilt for long
> periods (much more than 5 minutes) before worrying about
> overcharging, especially if I have a 9v adapter and/or higher
> capacity batteries. With high capacity batteries, it is getting
> close to impossible to "overcharge" the batteries even with a higher
> voltage adapter.

I agree that we could charge for a few minutes regardless of battery
capacity or charger voltage. It is definitely possible to overcharge the
batteries, though, so we still need a clever charging algorithm.

> Note that undercharging batteries is harmful to them also, not to
> mention frustrating to the users :-(.

Absolutely. I think we should change the FAQ, to specifically not
recommend 9V regulated adapters since they charge too slow, especially
when you have high capacity batteries.

Linus
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