If your inverter is in fact the same as ours, be advised that, on the inverter 3-position power switch, "power saver" means that the unit will be off... until it senses a load on the 120V side, then automatically turn on. Personally, I never use this position. If I need 120V circuits activated, I turn the toggle to the Power Saver OFF position. That will ensure the inverter turns ON and starts producing 120V. When I want it to. (Don't much like "automatic" stuff.)
When we first got our Agile, the alarm would frequently come on. We couldn't figure out what it was, but it seemed to have something to do with the High Point microwave -- my guess was that apparently the small 120V draw from the digital clock on the thing would just be enough to turn on the inverter, but then something would say "that's not enough of a load" and the inverter would go off... then on, then off, until the inverter switch was turned to Power Saver OFF. In the meantime, the alarm would be going off. Most annoying. I really don't know for sure, but I think the alarm was related to low battery power... but apparently that Power Saver business is somewhat sensitive!
While we were at the RT factory for charging system repairs I mentioned this. I don't know what they did, but somehow cured that particular issue -- we've never heard the alarm since, but I still will NOT use the "Power Saver" function; the switch is either in the center (OFF) position or in Power Saver OFF position (which means inverter ON). I know... almost as confusing as the %$#@ door step switch!
If I need 120V in the AM for my coffee, I turn the switch to the Power Saver OFF position, wait about 5 seconds, get one "BEEP" from the inverter, and the digital clock on the microwave lights up, indicating the presence of 120V. As soon as my coffee's done, I turn the inverter OFF (center position on the 3-way switch).
Incidentally, if your Agile is equipped with the compressor refrigerator, that thing is always looking for 120V -- if it senses its presence (inverter ON or plugged in to shore power), it will automatically switch to 120V operation.
Not sure if this is related or not, but maybe helps understand that %@%$! "Power Saver" function.
PS- FWIW, our Agile has two switches, one on the inverter and one on the control panel above the sliding door. The switch on the unit itself seems to have priority -- if it's turned on there, the wall switch is incapable of turning it off (hmmmm... and will seem like it's disconnected and/or not working...). In order for the inverter to really be off, BOTH switches must be in the center position.
I wonder if that's part of the problem -- if that inverter is left on (EITHER switch not in the center OFF position) while the RV is parked, it will drain the coach batteries very quickly... which will trigger a low voltage alarm... (don't ask).
And one more thing: I bet that "cord that looks like a phone cord" --RJ11, I think-- goes to the switch above the sliding door. That switch must be reading "ON" somehow, which is keeping the inverter activated and draining your batteries.
Whew! Sorry to ramble! Hope this helps...