Just how long can I expect the batteries on my son's new power chair to last? We just went to WalMart, he was at 100% fully charged (let it charge overnight) and after being there just about 20 minutes he was already down to 55%. We finished up and came home and he was at 30%. We parked kind of far out, but not that far out. I am still getting used to this full sized van and am a little nervous p…