Bought one last year, and I keep it plugged into the 12V
outlet in the TV antenna receptacle. Last week I decided to turn off the AC to the Airstream to give the converter a rest, and my electric bill. It costs around $15-18 a month to keep it plugged in. Well, after a week, I popped my head into the door and was horrified to see the voltmeter reading 11.6 volts! I quickly disconnected the battery and brought it inside, where I got out my good digital meter out and read the battery at 12.72 volts. Battery is setting on the Battery Minder inside a building that is heated to 45, unless I am working inside. I will have to do some investigation as to the descrepency in voltmeter readings. The only "phantom load" I am aware of is the radio/cd player that has a clock.