An electrified vehicle includes a traction battery that is operated according to a state of charge of the traction battery. A controller is programmed to operate the traction battery according to the state of charge of the traction battery and, in response to completion of a charge cycle of the traction battery, generates an adaptive relaxation time and an adaptive compensation voltage of the state of charge that changes with a temperature and a charge rate of the traction battery. The controller is further programmed to, in response to expiration of the adaptive relaxation time after completion of the charge cycle, update the state of charge to a value corresponding to a voltage defined by a difference between a measured voltage of the traction battery and the adaptive compensation voltage.