What was found
AFTER START WITH EMER LIGHT SWITCH IN ARM EMER LIGHTS NOT ARM CAS MESSAGE DISPLAYED. AFTER POH RESET PROCEDURE EMER LIGHTS STAY ON WHEN IN ARM POSITION. A FULL POWER RESET OF THE AIRPLANE DID NOT CORRECT THE ISSUE. "CORRECTIVE ACTION" REMOVED DEFECTIVE AFT EMERGENCY BATTERY PN 640-13560-00 SN 000803 AND INSTALLED CUSTOMER SUPPLIED MODIFIED EMERGENCY BATTERY PN 640-13560-00 SN 000826. COMPLIED WITH OPS CHECK, NO DEFECT NOTED. ALL WORK ACCOMPLISHED PER EMB PHENOM 300 AMM 33-52-00.