If you leave a caravan or motorhome leisure battery in a discharged condition, it is unlikely to recover. Some chargers are claimed to revive a neglected battery, but in most cases the damage is permanent. When a flat battery is left for several weeks, sulphate forms on its lead plates. When that happens it can no longer function as it should. This deposit prevents a battery from performing its intended functions. The photograph shows sulphate on the plates of a leisure battery that had to be replaced with a new one.