As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING SCHEDULED HEAVY CHECK EPSU BATTERY 12WL EXT R FAILED EMER TEST. AIRCRAFT WAS NOT GROUNDED. REMOVED AND REPLACED EPSU BATTERY 12WL EXT R IAW AMM 33-51-38-000-002-A/33-51-38-400-002-A. OPS CHECK GOOD. AIRCRAFT WAS RETURNED TO SERVICE.