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Subject: Re: What model and mask version for the badly charging units?
From: TP Diffenbach (rockbox_at_diffenbach.org)
Date: 2003-07-28


Quoting Stephen Ball <rockbox_at_invisionfilemanager.com>:

> OK I'll run it down tonight and try in the morning
>
> Do you want it completely from discharged and only near fully discharged?
>
> I just tried charging it, removed the charger, it said 100%, reboot and
> it now says 49%. Yet the Archos firmware (F1+Boot) says 100% and on the
> rockbox charge screen it says 96%
>
> :|

The battery percentages on the FM are rather unreliable. This shouldn't suprise us, as the battery percentage code was written for the Recorders.

Check the voltage. If the charge isn't plugged in and the voltage is 4.05 Volts, you're fully charged or as close to it as you'll get. If the charger is plugged in, you're fully charged if the battery shows 4.25, AND the external voltage is below some value that is at most about 1.5 Volts (it's definitely below 2). If when plugged, the battery read 4.25 but the external isn't low, you're not fully charged. I think we can exploit this information to, as the Archos software does, inform the user when the battery is fully charged.

Actually, I'm charging now, and the charging is taking longer than I expected, but then I've never really watched it closely before. I'm accumulating maybe 0.07 ( 7 one-hundreths) Volts every 10 (ten) minutes. I may be doing more poorly than I should because I'm watching the battery debug screen, which must be using some power.

The battery level without the charger is about .6 (.57 to .67) Volts less than with the charger, so while battery is displaying (about) 4.02 Volts, I'm guess than the "real" voltage without the charger would be about 3.2 Volts. So I'm about .85 Volts from a full charge. Assuming the charge is linear (and I don't think it is), I'm about .85/.7 = 1.2, 1.2 * 10 = 120 = 2 hours from a full charge. I began charging the /badly/ exhausted (2.9 Volts) battery 80 minutes ago.

If anyone has a better idea than I do how quickly charging /should/ occur, please let me know.

(As I finish this email, my battery level is showing only about 4.06 Volts while plugged, and 3.5 unplugged.)

--Tom

-- 
Archos FM has a Rockbox!



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