If the charger works on other carts we can rule it out. The melted post would mean you had a bad connection on that terminal. Double check all your cable connections and lug connections. Try checking each battery with a volt meter to see if one has reversed polarity. If you hook your volt meter to each battery make sure none are reading -6.3x. Do any cables get hot when you drive the cart? Does the charger receptacle get hot when your charging the cart?