Well I'll be damned,just when you thought you almost saw it all. Nice idea Dave!!,temporarily I mean.
They are perfect for seasonal vehicles and those that you don't drive too often.
There are even automatic switches that will shut off if the battery drains to a certain point so that you don't end up with a dead battery.
I.E. if you happen to leave your lights on. Once the battery gets down to a certain voltage it will automatically shut off power. You come back and find you have now power, hit the brakes, start your car and drive away.
Automatic Battery Disconnect Switch