Don't know if there's more to it, bu the Dome light fuse might just be to prevent the interior lights flattening the battery if the transit crews leave the lights on. (Picked up a new car once where exactly that had happened) Does anyone know any more about this subject?
I would think that at the docks where the cars are loaded and unloaded that the fob is probably left in the slot so the cars can be started and move in rapid order, so the fuse also probably controls the SE-SS and the immobilizer, which would place a draw on the system. Not positive but will try it this weekend.
I'd pull the 100A main fuse under the hood to kill the 12V battery - that's the last hop on the positive line before the positive terminal on the battery. I would concur with Evan's suggestion though and put a solar charger on instead.
Evan did you every check the voltage loss from the Low E glass in the Prius? I tried to get my automatic welding helmut to work with Toyota Low E and it wouldn't switch but would in sunlight. I wonder about the output from the solar panel behind Low E if it is significantly reduced.
Evan, where did you get this? Where did you put it in your car, can it be seen? Was it hard to install?
