I have the standard charging kit that came with my car. Right now it is plugged into my Nema 14-50 plug. I didn't drive my MS today so it is sitting at 80% battery charge. Should I plug I tonight before I go to bed, even though it won't charge? The green light on the unit is on. Is this using electricity? Or enough electricity that it is a "vampire" and I should unplug unless I'm charging?