Line Interactive APC UPS's don't do well with about 160 volts and 83 Hz
input. Apparently, you can only interact so much ....
Interacting with the line requires battery power. They can't charge and
supply power at the same time, unlike traditional online UPSes. Once
their batteries (LI type) go, they can't do anything.
Honest to God, APC replaced it because they said it should have tripped off
line with the line being that out of whack ...
APC is very good about replacing equipment that might be their fault.
Even after warranty. I've never seen another company with as smart,
techncial staff available quickly. Too bad no one has any real
experience with their big gear to see if its supported as well.