Joe,
I left the battery in the Overlander while plugged in for many winters.
However I found that the water soon disappeared out of the battery which
lead to its eventual demise. So lately I have been removing it and storing
it down in the basement for the winter. As you probably know we go through
more auto batteries in Wyoming than the folks in warmer climates. But that
is the price we pay to live next to great camping like Yellowstone Park.
Good luck, GAS