As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TEST ITEM 31 OF JIC 4-2020 FAILED BATTERY CAPACITY TEST. MESSAGE DISPLAYED AS FOLLOWS EPSU BAT CAP FWD L, EMER R EMER L, AFT L. TEST COMPLETION AT "CIDS" SHOWS BATTERY FAULT AT "EMERG PWR SUPPLY UNIT". 10WL LOCATED ABOVE CEILING DOOR FWD LT. REPLACED POWER SUPPLY IAW AMM 33-51-38 & BATTERY, TESTED OK.