As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOI - FLIGHT 2403 AFTER APU START, STANDBY BATTERY WOULD NOT GO BELOW 1.00. MAINTENANCE REMOVED AND REPLACED STANDBY BATTERY IAW Q400 MTC 6240001. C/W NORMAL APU START. RAN AIRCRAFT FOR APPROXIMATELY 5 MINUTES. ALL BATTERY INDICATIONS NORMAL. AIRCRAFT RETURNED TO SERVICE.