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 TWO MONTHS / 8 HOURS IN SERVICE. FLIGHT INSTRUMENTATION DISPLAYED "0%" BATTERY CHARGE STATUS AFTER NOT HAVING USED THE INSTRUMENT ON BACKUP POWER. BATTERY WOULD NOT CHARGE ABOVE 0%. NO "BATTERY FAULT" INDICATION PRESENT.