Sorry, maybe I didn't explain it well. If a battery gets really flat it cannot always be charged up again. You can try to charge dead car batteries but they may not keep the charge as well once they've been allowed to go flat. If you buy a new battery make sure you get someone to run the car for you for half hour or so, at least once a month if you're away or get a trickle charger, otherwise it'll happen again.
If someone runs it for tell them to keep your ICE off if you've got a mega install or it'll never charge up.