A battery control method includes: receiving a reprogramming request from a diagnostic device located outside of a vehicle to reprogram software of one or more electronic control units (ECUs) of the vehicle; performing reprogramming of the one or more ECUs or recharging of an auxiliary battery according to a number of the ECUs to be reprogrammed and whether or not a state of charge (SOC) of the auxiliary battery exceeds a critical value varied depending on the number of the ECUs to be reprogrammed; and sending a signal informing of the reprogramming or a warning signal associated with the recharging to the diagnostic device.