[Nut-upsdev] Any UPS hardware hackers ?

[Frank van Wensveen]

And now for something completely different... :-) And yes, it's
off-topic to this particular forum as it's not about NUT development.
<ducking>

Is there anyone around here who knows his way inside the hardware of
an APC Smart-UPS? The APC support division will not reveal _any_
details or service information, and the only descriptive documentation
I've found on the Web is in Russian.

The problem: I have an APC Smart-UPS 500 which has slowly increased
its battery float charge voltage over the years until now the 24V
battery is being float charged with 28.5V. This destroys the battery
in short order. 

Presumably some component has drifted off its nominal value over the
years. Finding out which one is difficult, though. The inverter's
power MOSFET stage doubles as a charging voltage regulator. The
MOSFETs are pulse width modulated by a driver signal coming from the
CPU and at least two chips with custom type numbers. Debugging the
processor system and PWM hardware is difficult because of the custom
chips on which I have no info at all.

Any response would be greatly appreciated!


Kind regards,
    Frank van Wensveen

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