I have a golden 3 wheel scooter dose charger

If the charger is working correctly, it should turn itself off automatically (may go into float chrarge depending on type of charger). There should be an LED or an amp meter on the charger to tell you when the charge is complete. When the batteries are charged, you should be able to leave the charger switched on and it should cause no harm UNLESS the charger is faulty, in which case it will continue charging and damage the batteries. You should be able to tell if this is happening as the batteries will become very warm. If the batteries are losing their charge after you have switched the charger off, it is most likely that your batteries need replacing. Failing that, you may have a short somewhere which unfortunately, could be difficult to find.