fridge

None of the outlets are powered with the car off unless you get a Mod from Costal Dave. You would then drain the Lead Acid battery is short order as it is quite small like a motorcycle or lawn tractor battery and does not have a lot of amp hours in it. You could leave the car on all night so the ICE would run periodically to keep things charged. Then you would be running off the main traction battery and the ICE. The lead acid battery is just to power up the system (computers) to get the car in a ready state. Get a combo electric and propane frig so you could keep it cold when the car is on using power from the car and propane when you are stopped (need I say out of the car? ). I had a Colman one that I liked my kids stole it and as far as I know it still works.

 

I bought a neat Vector 20L thermoelectric cooler/fridge that was on clearance at target for $30. It draws 3A and has a rechargable lead acid battery of its own (12AH) so it can keep itself going (up to) 4H. You can buy an accessory plug with battery clips to put directly on your battery, it will give power all the time, regardless of power state of the vehicle, but the cooler would drain your prius battery if you leave it run for more than a few hours, especially with other things draining power (lights, etc.) The cooler has a "battery protection" where it stops drawing current if voltage gets to 10.7A, I don't know if that's enough to start the car or not. From what I've read, 10.7A is pretty low and this is more to prevent damage to the battery than leave you with juice to start the car.

On the plus side, the cooler's battery can jump start the prius, if need be!