IF you want to remove the batteries, do so just like you would in a car or truck. Disconnect the negative terminal first, then disconnect the positive terminal and simply remove the battery.
You can also simply disconnect the battery and leave it right in place. Actually, the camper will probably be as cold as your garage anyway, unless you have a heated garage. You could also run an electric line to the camper and put a trickle charger on the battery. No need to bring it inside.
You CAN do this if you want, but no need to...really! If your camper is plugged in 24x7, the on-board system will keep the battery fully charged. Just check your water levels every now and then and you're good. Why take up bench space in your garage?
