I know there are battery "thingies" that plug into the lighter, which supposedly preserve the settings, but since the lighter is not "hot" whrn the car is not running, I don't see this working. How to do?
Google search returned this: how do i save the cars memory when replacing the 12v battery? | PriusChat I heard rumors that a 9v battery and some alligator clips on wires clipped to the front jump terminal works as well. :shrug: I'd be worried what happens when the 9v battery is connected to the 12v system though. Maybe risk of overheating, bursting?
Hook a low amp trickle charger to the the battery cables. Or pos to cable and neg to exposed metal. Be VERY careful to get it right way 'round. Then disconnect the battery, you should be fine, memories retained.