As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE REMOVING BATTERY FOR MAINTENANCE, FOUND NEGATIVE TERMINAL ON CONNECTOR ARCED AND BURNED. THE NEGATIVE POST IN BATTERY RECEPTACLE WAS ALSO DAMAGED AND POSSIBLY CAUSED BY WORN CONNECTOR (SOCKET ENLARGED) NOT PROVIDING GOOD CONTACT. CONNECTOR SHOULD BE CHECKED WITH GO/NO-GO GAUGE ANYTIME BATTERY MAINTENANCE IS PERFORMED. CONNECTOR AND RECEPTACLE REPLACED.