Congrats on your first weekend. Will have to say no to running an 18v battery because that could fry the Leopard’s little brain. That would be an expensive replacement. Do recommend batteries from Comet or Russell and would stay away from the battery stores. Buy the 9Ah over the 7.2. With a good battery, shouldn’t have to constantly use the battery charger. Does your engine not start after being run a couple of times without the charger?