The battery pack voltage is probably to low to activate the battery charger. Start with testing the battery pack voltage. Then check to make sure the plates aren't exposed. If the plates are exposed add distilled water until the plates are just barely covered. If they're 8 volt batteries use a 12 volt battery charger set on low amps and charge each battery individually until you get the pack voltage high enough to turn the golf cart battery charger on. You can charge each battery separately without unhooking any battery cables.