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Subject: Re: AW: AW: AW: Bug: Battery Charging with low voltage

Re: AW: AW: AW: Bug: Battery Charging with low voltage

From: Linus Nielsen Feltzing <>
Date: Thu, 03 Feb 2005 20:42:29 +0100

Matthias Klumpp wrote:
> During the day I tried with Archos SW flashed and your SW loaded from HDD.
> The JB did not hang up, but after 4h 12min the "Battery Charging" Pop-Up
> came.

This is because of the voltage "dips" when the battery is low, combined
with a bad grounding. The button driver thinks that OFF is pushed,
because the port pin for the OFF key shows a 0.

> The (flashed) FW was then possibly stopping and returned to the browse
> screen.

Yeah, the OFF key problem again.

> That way it was continuing chargeing, so I found it in this state (I was
> never seeing exactly the time it went to the browser).

> What do you think ?

Well, the batteries are obviously not charged enough. Or they are worn
out. I guess your usage pattern, where you charge them with a very low
voltage for only 30 minutes at a time, isn't very good for the batteries.

> I'll charge now again with Archos FW and I'll repeat that test to verify the
> 4h once again.

If you only get 4h play time from your 2000mAh batteries, even with the
Archos charging, something must be wrong, either with your batteries or
your jukebox hardware.

> Pointing out the test conditions, so I don't have to comment that in every
> mail from now on.
> All tests are done with these conditions (always the same):
> - Fully charging batteries with Archos FW flashed until it shows "Charging
> completed".

I believe that the Archos algorithm isn't very sophisticated, so it
doesn't properly determine that the batteries are really full.

> I then found out, that 9V and Archos FW works 100%.
> So I thought it can't be a "principle" problem, but it must be a SW problem.
> If Archos is able to do so, Rockbox also could be able (ok - charging
> philosophie might be different).

Yes, the Archos algorithm seems a lot simpler.

> Just to point that out once again:
> My intention is NOT to get batteries FULLY charged in the car.
> I only would like to have at least a condition, that keeps my JB alive for
> long time while being connected to the charger.

I see.

> I'm using 2000mAh batteries.
> Do you think it's worth to repeat the test of your SW with some lower
> capacity batteries ?

Nope. That won't help, unless the 2000mAh batteries are bad.

> Wouldn't it be a possible way (or better workaround) to implement something
> like a "aggressive charging mode", user configurable in the settings:
> - start charging immediately after the charger is detected


> - we already have the bat. capacity in the settings
> - there could be a 2nd parameter where the user specifies the charging
> voltage (don't know if RB can get it from ADC)

I have some ideas about finding out the charging voltage, but the best
might be to have a setting for it.

> - same way you calculated, the FW could estimate the current and that way
> the total charging time (aproximatly)
> - you then set the timeout (when charging stops) to that value


> For sure this is not the best way to charge batteries and probably it is
> able to kill the batteries, therefore it's called "aggressive" ;-)))

Well, charging with a too low voltage for a long time is not what I call
aggressive. :-)

> As increasing the charger voltage will not solve my problem (as m.a.), any
> ideas what could be done ?

Not really, other than starting the charging immediately instead of
waiting for a stable battery voltage reading.

Received on 2005-02-03

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