I have an Artnin scooter with a 48v down tube,replacing the 36v it came with. I was thinking of making another floorboard, raising it 3 inches w/reinforcement and put a 48v or 52v in between. Can I combine the POS/NEG wires then connect to controller? Only one battery will be used at a time. Being a disabled vet and this is my ONLY transportation battery packs are about half price and I need the two batteries