Gripper put mine in six months ago and I've never had to take the battery out to charge at all
Oi! go to work!
This is the ones we fit to our vans:http://www.ebay.co.uk/itm/T-MAX-12-VOLT-SPLIT-CHARGE-DUEL-BATTERY-SYSTEM-WITH-LED-DISPLAY-FOR-LAND-ROVER-/221126393969?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item337c290071