What was found
AFTER TAKE-OFF WE GOT CAS MESSAGE BATTERY OTEMP L. ACCOMPLISHED EMERGENCY/ABNORMAL PROCEDURES CHECKLIST. LANDING GEAR WOULD NOT EXTEND. ACCOMPLISHED EMERGENCY/ABNORMAL CHECKLIST. PULLED LANDING GEAR BLOWDOWN HANDLE. REMOVED AND REPLACED LT MAIN BATTERY WITH AN OVERHAULED UNIT. OPERATIONS CHECK IS GOOD. BATTERY OTEMP L CAS MESSAGE WAS NOT ACTIVE BEFORE OR AFTER THE BATTERY REPLACEMENT. BATTERY OFF L (R) CAS MESSAGE WILL DISPLAY ON CAS WITH BOTH ENGINES RUNNING AND BATTERY SWITCH OFF. WORK DONE IAW CESSNA 680 AMM, REV 29, CH 24-31-00. OVERHAUL PERFORMED BY BOEING DISTRIBUTION INC., CRS RD42488M, WO 2000385919.