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Subject: RE: to weak batteries - cant even charge... ;-(
From: VanBaren, Gerald (AGRE) (Gerald.VanBaren_at_smiths-aerospace.com)
Date: 2004-09-15


> -----Original Message-----
> From: rockbox-bounces_at_cool.haxx.se
> [mailto:rockbox-bounces_at_cool.haxx.se]On Behalf Of karl
> 'the_angry_angel'
> southern
> Sent: Wednesday, September 15, 2004 5:17 AM
> To: Rockbox development
> Subject: Re: to weak batteries - cant even charge... ;-(
>
>
> >
> >
> >I think it would be a good idea to fix this before V2.3 is shipped.
> >
> >The fix seems to be to start charging immediately, then
> after a minute or
> >so, measure the battery voltage and see if charging should
> continue or not.
> >
> Maybe I'm being ignorant of some feature (and if I am, ignore
> this), but
> I dont think that this is the best solution. If the batteries become
> 'overcharged' the electrolyte inside them will evaporate
> overtime. Over
> weeks/months, if the batteries are fully charged when this process
> starts, wont this shorten the battery lifespan? Or am I being
> too cautious?
>
> --
> Karl 'the_angry_angel' Southern
> http://theangryangel.is-a-geek.com/

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.

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.

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

Reference:
  "Rechargeable Batteries Applications Handbook"
  by the Technical Marketing Staff of Gates Energy Products
  Publisher: Newnes; (November 26, 1997)
  ISBN: 0750670061
  http://www.amazon.com/exec/obidos/tg/detail/-/0750670061?v=glance

gvb

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