CHARGER PROBLEM

Had XB-600 for a year now. It still runs good, weak up hills thow. I may cooked/gassed (smell of rotten eggs, Hydrogen sulfide discharge?) my batteries during my first few charges. Only holds a charge for five to ten miles. The stock charger is a piece of junk. Green light don't come on and does not auto shut off! Question; Where can I get a good quality 48v charger?