What was found
EMERGENCY BATTERY CHARGES BUT WILL NOT KEEP CHARGE. EMERGENCY LIGHT WILL NOT ILLUMINATE 2 HRS AFTER ACFT SHUTDOWN. GAINED ACCESS TO THE #1 & 4 BATTERY PACKS & SWAPPED THEM FOR TROUBLESHOOTING. ALLOWED BATTERIES TO CHARGE & WAITED 2 HRS AFTER POWERING DOWN. AFTER 2 HRS, POWERED ON EMERGENCY LIGHT & FOUND THEY TURNED ON. TURNED OFF EMERGENCY LIGHT SWITCH & EMERGENCY LIGHTS STAYED ON, FOUND NR 3 G-SWITCH TRIPPED. RESET SWITCH & SWAPPED BACK BATTERIES. LET THE PLANE COLD SOAK FOR 2 HRS & PERFORMED OPS CHECKS & FOUND WITH BATTERY DISCONNECTED SHOULD HAVE EMERGENCY LIGHTS COME ON IN ON & ARM POSITION. ONLY GETTING LIGHTS TO COME ON IN ON POSITION. SUSPECT NR 4 BATTERY FAULTY. WORK PERFORMED IAW MM 33-50-07. REVIEWED MAINTENANCE & FOUND NR 1 NEEDED TO BE REPLACED. REMOVED NR 1 BATTERY DUE TO INTERNAL FAILURE, & INSTALLED REPAIRED BATTERY IAW AMM 33-50-07. PERFORMED OPS CHECK IAW AMM 33- 50-00, FOUND TEST SATISFACTORY. ORIGINAL SUBMISSION DATE: 1/9/2024.