Do NOT do what Mudsufer just said unless it's not a primary radio and you only want to use it for the sim. It can't be just any 9V converter either, it has to be a certain amount of amps too otherwise it will kill your radio. My suggestion is not to do this at all.

The simulator uses very little battery life because it turns off the RF function when you plug in the buddy cord. I go about 10 days of use on my JR before I need a charge.