As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EICAS MESSAGES: MAIN BATTERY AND BATTERY CHARGER MAIN ELEC STANDBY DISPLAYED. ACCOMPLISHED TROUBLESHOOTING IAW MAINT MESSAGE. SWAPPED MAIN BAT CHARGER WITH APU BATTERY CHARGER, NO HELP. REPLACED MAIN BATTERY, ELEC STANDBY MESSAGE REMAINED. RESET IAW 24-09 TASK 820. SYS OK.