As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHX - EEL - DURING OVERNIGHT MAINTENANCE THE EMERGENCY LIGHT SYSTEM TEST "OK" LIGHT WOULD NOT ILLUMINATE AND RECEIVED MESSAGES "COMM EMER R" AND "BATTERY EMER R". MAINTENANCE REMOVED AND REPLACED THE RT OVERWING EMERGENCY POWER SUPPLY BATTERY. OPERATIONAL CHECKS WERE GOOD.