What was found
GENERATORS FAILED SHORTLY AFTER TAKEOFF. STARTED LOSING ELECTRICAL POWER BY EVIDENCE OF THE AIR CONDITIONING FANS TURNING OFF, GETTING FLAGS ON THE EFIS SCREENS, AND EVENTUALLY LOSING ALL AVIONICS POWER. HAD TO MANUALLY PUMP GEAR DOWN FOR LANDING. AFTER AN UNEVENTFUL LANDING, ALL OF THE SYSTEMS STARTED POWERING BACK ON. PERFORMED MULTIPLE INSPECTIONS OF THE ELECTRICAL SYSTEMS. NO ISSUES WERE FOUND, EXCEPT THAT THE MAIN BATTERY DID NOT PASS THE CAPACITY CHECK. BATTERY WAS REPLACED WITH A NEW UNIT AND RAN ACFT TO TRY TO DUPLICATE THE ISSUE. MAINTENANCE WAS NOT ABLE TO DUPLICATE THE ISSUE.