Please read THIS THREAD
in its entirety. All you will need to do is to disengage the IOD fuse. IF, however, the SMI brake is the culprit draining your battery, you may have to run 12v power from the RV to the SMI unit. (Very easy to do) Disengaging the IOD fuse keeps the Wranglers parasitic specific power draw from draining the '07, '08 Wrangler battery.