Does anyone know how to adjust the voltage at which an APC Smart-UPS floats
its batteries? Their factory default at room temperature seems to be about
2.33V/cell, which exceeds the manufacturer-recommended voltages for every
sealed-lead acid battery I've looked up (equivalent to 14.0V on a 12V string).

We've had to replace batteries these UPSes every 2-3 years, on average,
probably as a result of electrolyte loss from the high charging voltage.

On smaller APCs (Back-UPS line), it's easy enough to tweak a trim pot inside
and turn down the charging voltage. This decreases the runtime slightly, but
does halp the batteries last longer. But Smart-UPSes have no such adjustment
pot... their charging regime seems to be under the microprocessor's control.

Can this be controlled from an attached PC through the serial interface?
APC's tools seem to offer no such option, but I've heard rumors about an
undocumented calibration procedure.

Failing that, any suggestions on physically modifying one to drop the float
level a bit? I've thought about changing the thermistor circuit to fool the
UPS into seeing a higher internal temperature (charging is supposedly
temperature-correlated), but then it would probably run its fan constantly.