SURT10000XLT - CHARGER PROBLEM - FIXABLE?

[BillP]

Like many APC efficient designs of 10kVA and up; TWO DC Busses are used to feed the inverter, one for the +ve half and one for the -ve half. Each has an open circuit voltage of about 200 volts. The SURT10000XLT is no different.
We have a SURT10000XLT unit in the shop for evaluation to determine if this unit will become electronic junk or for some reasonable amount can be repaired. I don't see too many folks who have worked on this unit with postings. That probably just means that most said NAY NAY, I'm too tall for that product and made it junk right away.
I've had two units of this exact size fail badly in the last 6 months so I'm sure that I am not alone with problems on this unit.
Our unit conditions are: (1) unit must have battery connected to start up - 4 strings of 96 volts each (2) utility on and power switch on - turns fans on (3) Pressing 1 [test] button runs on battery for a bit and then goes to normal with top green sinewave LED on and a couple of battery LED'S illuminated (4)After the unit destroyed our NEW batteries, we have some used ones for this testing that are not fully charged, so the few battery LED's on seams normal.
We know that the unit is not normal however because one side of the charger is putting out nothing because the DC reading is the same as the open circuit voltage of the batteries, while the other side is putting out 235 volts - meaning that those batteries will soon explode or overheat at least. The charge voltage should be between 216 and 218 volts.
With what appears to be only ONE mother board for everything, the charger looks like it's on there too. The question is then - does anyone know besides the designer where the charger is, what to test next, are parts sold by APC, and whether it's just a $5000 junk box?