As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN- DAYLIGHT CONDITIONS, OAT +80F, ON COMING CAPTAIN STATED HALF OF THE EMERGENCY LIGHTS FAILED TO ILLUMINATE ON PREFLIGHT. UTILIZED THE APU GENERATOR TO RECHARGE THE (EMERGENCY POWER SUPPLY) BATTERIES WITH NO FURTHER ISSUES. THIS SDR IS BEING SUBMITTED PER 14 CFR 121/703 (17).