Is your issue only happening when hooked to two 6v batteries in the house....??

Like KAG said, these units have an automatic shutoff when they sense low power...

Not only does the unit use 12v power, it also needs a [u]minimum[/] 1amp of continuous supply...

I would suggest either get a 12v lawnmower or similar small battery or make a 120v to 12v converter with a minimum 1amp (1000ma) output...

Don't forget the 3amp fuse...

Rickie