Thanks for the reply, the battery going dead early would cause exactly
what it is doing, I been going down the path of the frequency wasn't
correct to make the MOSFETs switch on and off fast enough to create the
proper voltage coming out of the transformer.

A couple of things came to mind...

1. The 10:1 ratio in the transformer would create 106 volts if the
battery had suddenly dropped to 10.6 volts (normally this would be
120VAC from 12VDC), if the the battery voltage kept doing down so would
the output voltage.

2. When I equated this to the last time my car would not start because
the battery was trying to die it all made sense.

When I get the thing re-assembled I'll monitor what the battery voltage
is doing when the unit looses power.

More later...


loedown wrote:
The SLA battery you are talking about is most likely going to be the
culprit, although it stays at 12V after you unplug it, you have to check the
battery under load conditions. Very common for the battery to die and the
explanation that it starts at 106VAC and goes down hill from there fairly
rapidly points squarely at the battery, UPS draw reasonable current and the
battery can't keep up. Mind you, I don't have the unit in front of me.

Paul