well i was working on my truck outside and some guy stops by asking for help with his ninja.. so i said i'd look at it and see what i could do or find out. well i think the battery needs to charged.. tried to turn it over and it was doing OK.. not great but ok.. and i tried the lights and it just died. can i use a normal battery charger for a car on this battery? it has 6 and 12 volt capablility.. any other ideas what it might be?