said by bemis:
Something to think about it... most affordable UPS' will not work when connected to a small generator. The UPS will declare the power to be bad and refuse to charge and in some (all actually I think?) cases that means the devices plugged in go dark when the UPS battery dies.
I've heard that it has to do with variability in the frequency and that larger generators do not have the problem, that may be true, I don't know... I do know that my UPS will not charge from my 4500W generator...
My UPS will also not charge from the 1500W inverter that I use on a large 12V marine battery... in that case I'm told it's because my inverter is a square wave output, not sine wave... I prefer the battery and inverter in power loss situation because it makes no noise, generates no fumes and I can set it up without going outside.
I would find someone with a O-Scope and a good Peak/RMS reading Digital multimeter.
Take a good look at exactly what kind of waveform you are getting off the inverter, and no matter what type or size of generator you are using, you need to calibrate it on a routine basis.
I have the "better" Honda 3.5kw generator, and the APC Smart UPS, but, you still have to put a meter that reads line frequency on it and make sure that thing is set dead at 60Hz.
It's going to vary a bit between no-load, moderate-load, and full-load, but depending what the sensitivity adjustment is set to on the UPS, something as little as +/- 1Hz off from 60Hz will drive UPS's crazy.
Check the manual for your specific model, but the frequency adjustment should be on, or around, the carburetor.
Read the instructions for the UPS to see how to turn down the sensitivity, it may be via an external button, or you may need to hook up to the serial port and change it via software.
If it's a line-interactive UPS, the software settings should also let you set the high an low trip points, where the UPS stops trying to compensate for a bad line voltage and switches to battery.
Some times the factory settings are set a bit tight(114-126v), but you can widen the range to probably 106-134v without any problems.--
ROCK 'TIL SUNSET