Originally Posted By: ducktapeguy
Unless you get the more expensive UPS systems, most of the ones for home computers are modified sine.


Really? That's surprising, though it makes sense from a cost POV. It must be a much better modified sine than I get with my other inverters. There's no noise, buzzing, or overheating at all, which is why I like them for my low-draw, sensitive gear.

Originally Posted By: ducktapeguy
You can't plug them into another modified sine wave UPS, because it sees an irregular waverform and automatically switches to battery, which is what it's supposed to do.


I'm not entirely convinced of that, though I confess my research is incomplete. For example, I have two older ones (a Belkin and an APC) and have plugged them into a modified sine inverter in an attempt to clean up the power on the non-UPS outlets. That side works, though not all the noise is gone.

Both UPS units have dead batteries, so I'll need to swap them out to see if a modified sine will charge the internal battery. It doesn't matter much since it's easier pull straight DC from an external battery and solar panels. The only issue is a reset if I lose a connection (IIRC it's the APC that locks up).