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Subject: RE: Battery charging with a power supply unit

RE: Battery charging with a power supply unit

From: Jammit Timmaj <>
Date: Tue, 22 Sep 2009 02:40:10 +0000

> From:
> To:
> Subject: RE: Battery charging with a power supply unit
> Date: Mon, 21 Sep 2009 00:12:52 +0100
> > Helo listers,
> >
> > i want to charge the battery of my Ipod video with a power suply unit,
> > but it doesn't work. The battery level for example is at 50 %, I Try to
> > charge and after ten hours it is still 50 %. I only could charge the
> > battery with the USB cable with my PC. What have I to do to Charge the
> > battery with the power supply unit? Any tips?
> >
> > best regards,
> >
> > Thorsten
> Hi,
> What version of Rockbox are you using? I'm using a build from 30-06-2009
> (R21158) and it works fine. I have tried both with the PowerMonkey portable
> battery charger and with the AC mains plug that ships with the PowerMonkey
> connected to the iPod connector. Whilst charging the battery level shown on
> the display does not change, but as soon as the power supply is disconnected
> the level is updated to correctly reflect the new charged level.
> I think older builds (going back a few months or more) had issues with AC
> charging. I'd suggest you try a new build, or a daily one. You can back up
> your current configuration to revert to it if you're not happy with the
> update.
> Best,
> H.
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Cool! I can finally answer a question with technical knowledge that I actually know about.

For the USB standard, the device won't pull any current until both the
data+ and the data- are also connected to a voltage source of 2.5 volts
through a resistor. The easiest way of doing this is to make two
voltage dividers with 30K resistors. Apply 5v and ground to each divider, then connect a wire from each divider tap to the data+ and data-. The dividers split the 5v into 2.5v, and the two 30k resistors in series act like a 15k resistor to the data pins.

This lady has one way of doing this. Her website is She uses an external battery of 3v (close enough to 2.5v) connected to the data lines through a 100K resistor. She uses 100K for safety, but it'll work safely with anything above 1K. 100K is probably getting close to too large.

Almost all iPods (except the really new ones) have an input for Firewire. Except for the first iPod, this input is only used for charging. All that input needs is anything from 9 volts to 20 volts. This website has all the pinouts you'd need If you need a way to connect up stuff to your iPod, you'll need a connector. You could try this place

If you need a schematic (a picture is worth a thousand words), let me know and I'll try to post a picture. I hope I've helped.
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Received on 2009-09-22

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