What was found
EMERGENCY POWER TEST FAIL ON PREFLIGHT CHECK. PREMATURE REMOVAL/INSTALLATION, OFF MPN: 31433-001, POS: 2, SRL: 10200007, TAG NR: F40369 ON MPN: 31433-001, CPN: 2412387, SRL: 10103712, TAG NR: 384D35, REASON CODE: PREMATURE REMOVAL/INSTALLATION, OFF MPN: 31433-001, POS: 1, SRL: 10104164, TAG NR: 3E0477, ON MPN: 31433-001, CPN: 2412387, SRL: 10101944, TAG NR: 7217E2. MCO U REPLACED BOTH MAIN ACFT BATTERIES. CHECKS NORMAL. 2 EMERGENCY POWER TESTS COMPLETED, AND BATTERY CHARGER CHECKED NORMAL. REF: MM 24-34-02-4.