As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING POWER FAILURE L1,L2,R2 AND LEFT OVERWING EXIT EMERGENCY LIGHTS ARE NOT ILLUMINATING. / PREFORMED OPS TEST OF EPSU BATTERIES. FOUND EPSU FORWARD AND AFT BATTERIES FAILED. REMOVED AND REPLACED BOTH BATTERIES IAW AMM 33-51-38. OPS CHECK GOOD."