Another fun fact I discovered the hard way is that many APC UPSes refuse to go back into bypass when they are supplied by a small generator with a dirty wavefor

Another fun fact I discovered the hard way is that many APC UPSes refuse to go back into bypass when they are supplied by a small generator with a dirty waveform. We had quite a few APC units in the 1990s and 2000s, and I had the impression the older ones were easier on batteries. We were on a three year replacement cycle until Y2K, and after that we found it necessary to check the batteries every six months or so in the newer units.