Backup battery discharged -> GTA01 and GTA02 dead

Werner Almesberger werner at
Sun Jul 20 04:56:06 CEST 2008

Ben Wilson wrote:
> but some battery packs have electronics inside and you can?t just charge  
> them like you would a normal battery.

Ours have two types of internal electronics: a protection circuit that
can deny access to the battery, and a Coulomb counter that keeps track
of the battery status, but does not interfere with its use.

GTA01 batteries only have the protection circuit, GTA02 batteries have
both types of circuit.

The protection circuit cuts the battery off if it is discharged to too
low a voltage. When sufficient energy is applied at the battery
terminals, the protection circuit opens the access to the battery
again, and allows it to charge.

At this level, whatever the Coulomb counter thinks the battery is
doing is of no relevance. The Coulomb counter only comes into play
when we want to know the exact charge status and similar parameters,
but no such knowledge is needed for the charger logic of the PMU to
charge a battery.

- Werner

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