As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
REFERENCE LP702388 #1 EPSU BATTERY (13WL) AFT L FAILED TEST FAILED EPSU SYS TEST. AC WAS NOT GROUNDED AS A RESULT OF THIS SDR REPORTABLE EVENT, IT WAS A RON SCHEDULED HEAVY CHECK. REMOVED AND REPLACED EPSU BATTERY (13WL) IAW AMM 33-51-38-000/400-002-A. OPS CHECK GOOD. AC OK FOR SERVICE.