What was found
ELT BATTERY DUE REPLACEMENT. INSPECTED ELT PER FAR 91.207 (D). NO DEFECTS NOTED. REPLACED BATTERY WITH NEW ARTEX P/N 00-60-62. ASSEMBLED COVER ON ELT (BATTERY PLUG IS FOOL PROOF, CAN ONLY CONNECT ONE WAY. COLOR CODED WIRES MATCHED). BATTERY EXPLODED WITHIN 30 MINUTES, BEFORE FUNCTION CHECK WITH NEW BATTERY. ELT WAS NOT INSTALLED IN AIRCRAFT AT TIME OF EXPLOSION. NO VISIBLE BARE WIRE EXPOSED. BATTERY MANUFACTURER WAS CONTACTED. ELT INSTALLED NEW IN 1986.