As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GARMIN G5 FLIGHT INSTRUMENT BACKUP BATTERY FAILED AFTER APPROXIMATELY FOUR MONTHS / 16 HOURS IN SERVICE. FLIGHT INSTRUMENTATION DISPLAYED "1%" BATTERY CHARGE STATUS AFTER NOT HAVING USED THE INSTRUMENT ON BACKUP POWER. BATTERY WOULD NOT CHARGE ABOVE 1%. "BATTERY FAULT" INDICATION WOULD INTERMITTENTLY APPEAR.