What was found
IN CRUISE NOTICED CABIN EMER LIGHTS ON WITH SWITCH IN ARM POSITION. LATER, CABIN EMER LIGHTS BEGAN TURNING ON AND OFF RAPIDLY. PERFORMED TROUBLESHOOTING OF THE EMERGENCY LIGHTS BY CHARGING BATTERIES FOR 60 MINUTES TO TOP CHARGE. BATTERIES STAYED ILLUMINATED. ISOLATED EACH BATTERY POWER SUPPLY BY REMOVING EACH ONE AT A TIME. FOUND THE AFT POWER SUPPLY TO BE FAULTY. NOTIFIED MCC OF FINDINGS. REMOVED AFT BATTERY & INSTALLED TESTED BATTERY IAW AMM 33-52-01. OPS CHECK GOOD.