I replaced my battery in my 13.5 hp Murry riding mower. I got two starts on it and the battery died. I had the battery tested and it was good. I was told the starting solenoid would not be the problem. The battery is not getting recharged. The key is in the off position, my lights are not draining the battery. I was looking to see if the alternator is bad, but I don't think this engine has one according to the manual? Any other suggestions?