From the manufacturer's website FAQ:
'To avoid another question, I will first explain what a battery isolator is:
A battery isolator is basically an electrical switch that connects the trailer's battery to the tow vehicle's alternator when the alternator is charging (engine running) and disconnects it when the alternator isn't charging (engine off). A battery isolator prevents you from draining the tow vehicle's battery when you are using the trailer DC (So you can start your engine in the morning).
You can achieve the same result by unplugging the trailer connector every time you shut off your engine and connecting it after you start the engine. But, if you forget to disconnect it, you may have a dead battery; and if you forget to reconnect it, you won't have tail lights or trailer brakes.'
Sounded like a good idea to me.
Hanging out in Oregon.