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Subject: Re: New charging algorithm

Re: New charging algorithm

From: Jerry Van Baren <gerald.vanbaren_at_smiths-aerospace.com>
Date: 2005-03-11

claus wrote:
> Hello all,
>
> I just installed and flashed CVS-050311 on my
> Jukebox Recorder 10 v1. I upgraded from v2.3.
>
> I wonder if there is already a part of the new
> charging algorithm since I observe ...
>
> when being plugged in using a regulated 9V charger (yes I know this is
> too weak:) batterie indicator shows 100 and trickle charging
> then I unplug it an the indcator drops to 95.
> I replug it and it shows 100 again.
>
> Is this normal?
>
> BTW: I really appreciate that the initial <?> has gone in the battery
> indicator. And rockbox seems a lot more responsive since 2.3 perhaps
> only an impression but any way I *really* like rockbox.
>
> Thanx and regards,
> Claus

Yes and no, the 100%/95% is sort of a side effect of the recharge
change. There is a rule, held over from the original code, is that
anytime the charger is being run in "trickle" mode, the display shows
100% because trickle charge implies the batteries are full.

One of my changes is to start and run the charger at "trickle" charge if
the battery is equal to or above 95% level (the level was picked
semi-arbitrarily). The side effect of this is that, since your
batteries are nearly full, the charge starts at the "trickle" level and
thus the display shows 100%. The previous algorithm waited till the
battery was discharged to the 85% level before doing _any_ charging,
therefore your display (and battery) previously would tick down to 85%,
at which time a full charge cycle would commence.

The problem we face is that trickle (and top-off) charge is a close-loop
control that drives the battery at a specific voltage level (5.45v/5.64v
IIRC). Since we figure out the battery's charge by reading the battery
voltage, we have no useful observable indication of the battery's charge
when we are in these modes (theoretically we could look at the charge
"on" time duty cycle to estimate how much current is going into the
battery in these modes, but that varies significantly based on the
charger input voltage).

Trivia:

Battery Starting charge level
------- ---------------------
  0%-85% full charge
85%-95% top-off charge
95%-100% trickle charge

A 9v charger supply is acceptable, it just won't recharge your batteries
as fast.

gvb
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Received on Fri Mar 11 18:46:16 2005


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