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Subject: Re: Battery voltage and ext. power voltage in debug battery info page
From: Heikki Hannikainen (
Date: 2002-08-14


On Wed, 14 Aug 2002, Uwe Freese wrote:

> The debug output tells me while charging for ex.
> Battery: 5,77 v
> External: 5,25 v
> It irritates me that the external power voltage is lower than the
> batteries' voltage and charging is still possible. Is that because of
> a "stepup" voltage regulator or something? Is this the part the
> "charge" pin of the sh1 switches on and off for charging the
> batteries?

  Hum - for me the external voltage shows always a 1-3v more than
the battery voltage (the stock charger I have supplies almost 9volts when
idle, according to the 'ext' voltage). The scaling factor used for
converting the value returned from the external voltage A/D converter to
volts might be wrong though - it should be checked with a multimeter! We
only use the ext voltage for determining if a charger is connected.

  The ext voltage is measured before the charging regulator, check the
interface board schematics at ... the
regulator is actually a MC34063A, 1.5 A step-up/step-down/inverting
switching regulator, which can step-up the voltage if needed. I haven't
calculated what the circuit used actually does.

  - Hessu

Page was last modified "Jan 10 2012" The Rockbox Crew