Dimensions Inverter Problems

I just read the PDF file on this inverter from SENSATA TECHNOLOGIES.

They want fifty dollars for the device

It has a FIFTEEN AMP rated 120vac transfer switch

It is modified sine wave

If it's turned on, it will run the battery down even with no load applied. That's not unusual.

It's also not at all uncommon to have the inverter wired to the battery bank without going through the disconnect relay. It can use quite a bit of current (depending on the size, of course), and may very well exceed the ratings of the disconnect relay's contacts. Even if it didn't, the additional voltage drop from the relay contacts and the extra wire length is better avoided.

It sounds like it indeed isn't working as it should, from your brief description. There's no harm in leaving it disconnected from the battery; in this case, that sounds like a very smart course of action. It may be repairable, but likely not economically. If it's not under warranty, I'd suggest researching a replacement unit. (If it is merely its transfer switch relay that is not operating on it, replacing that could be a straightforward and not too expensive repair.)