AN UNPLANNED IGNITION OF HYDROGEN GAS OCCURRED ON 7/5/01 IN MAIN WEST BATTERY BARN WHEN FRESHLY CHARGED BATTERY WAS PLUGGED INTO #30 RAMCAR AND SWITCH TURNED. AN OPERATOR HEARD A SIZZLE THEN A LOUD BANG. A FAULTY PLUG ON BATTERY IS SUSPECTED OF DRAWING AN ARC THAT IGNITED GAS UNDER LIDS.