As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLEANING AND INSPECTING OF BATTERY CHARGER FOUND SIGNS OF ARCING ON BATTERY CHARGER AND ON TERMINAL. REMOVED AND INSTALLED MAIN BATTERY CHARGER IAW B737-900 AMM 24-31-21-400-802-001. INSTALLED TERMINAL LUG ON POSITIVE SIDE WIRE IAW B737-900 SWPM 20-30-11. PERFORMED MAIN BATTERY CHARGER OPS CHECK IAW B737-900 AMM 31-21-710-801, OPS CHECK GOOD.