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Subject: Re: Bug: Battery Charging with low voltage

Re: Bug: Battery Charging with low voltage

From: Jerry Van Baren <gerald.vanbaren_at_smiths-aerospace.com>
Date: 2005-01-31

Matthias Klumpp wrote:
> Hi all,
>
> I'm observing by own experience and due to the fact that this topic is
> posted very often, that the battery charging of Rockbox is unfortunately one
> of the weak features.
>
> I was once mentioning a problem (unfortunately uncommented until now :-?),
> that the batteries were discharged with USB connection:
> http://www.rockbox.org/mail/archive/rockbox-archive-2004-11/0067.shtml
>
> Since some time, I'm facing another problem, were my JBRV1 is running out of
> battery power.
>
> Here's a short description about what is happening:
> - JBR V1 with Rockbox 2.3 flashed
> - 2000mAh NiMH batteries
> - deep discharge: on (see also tests below)
> - trickle charge: off
> - battery capacity: 2000
> - car adapter mode: on
>
> I'm operating the JB only in the car, with a car adapter connected always.
> That adapter supplies with 9V max. 1A (original Archos adapter supplies with
> 11.5V).
> After more or less 3-4h of continuos playing, the JB is shutting down with a
> ATA Error because of low power.
> The problem is always (and reproducable) occuring in that condition.
> If the JB is switched on/off after e.g, 1h of driving, the problem is not
> occuring.
> Before using the JBR, I was owning a JB Studio with Rockbox 2.2 and that
> worked perfectly with the same adapter.

[snip]

> Best regards
>
> Matthias

Question: Is your power plug switched with the car ignition (most are)?
  If so, you are NOT powering your RockBox constantly as you imply by
stating that it is connected always. This likely is a big part of the
problem. I'll continue under this assumption...

See the battery FAQ #2
http://www.rockbox.org/docs/battery-faq.html

My advice is do NOT turn deep discharge on because that causes RockBox
to run on batteries until the batteries are nearly exhausted and then it
recharges. The problem is that your batteries, on average, will be only
half full :-/ at the best of times. If your power source is switched
with the ignition, this will really mess up the RockBox charging
algorithm because the algorithm has various delays, etc. to try to
coddle the batteries. IMHO, deep discharge is not a good thing
generally and is really bad in your case.

My further advice is to turn trickle charge ON. This attempts to keep
the batteries fully charged, which is what you want to do (again, IMHO).
  Again, if your power is switched by the ignition, RockBox's battery
coddling algorithm is not very quick to start charging nor at all
aggressive in its charging.

Archo's battery charging algorithm is probably:
1) Start charging immediately
2) Charge full tilt until you see a peak or a many hour time limit expires.
This is much more aggressive than RockBox.

gvb
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Received on Mon Jan 31 22:44:36 2005


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