As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PERFORMANCE OF T/C 78233001 EMERGENCY BATTERY PACK CAPACITY FUNCTIONAL CHECK- AFT L/H BANK OF INTERIOR LIGHTS AND 3 MOST AFT L/H EXTERIOR LIGHTS FAILED TO STAY ON THE REQUIRED 15 MINUTES. GROUNDED - YES. REMOVED AND REPLACED M1673, EMERGENCY LIGHT POWER SUPPLY, OPERATIONAL TEST NORMAL. REF B737-800 AMM 33-51-06-960-806.