As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING HEAVY MAINTENANCE, EPSU BATTERY 13WL FAILED TEST, REF LHT NR 5000852972-0010. REMOVED EPSU WITH LOW VOLTAGE IAW AMM 33-51-38-000-001-A REV 76. INSTALLED NEW EPSU IAW AMM 33-51-38-400-001-A REV 76. OPS TEST OK IAW AMM 33-51-38-740-050-B REV 76.