A battery assembly for use in an aircraft. The battery assembly may include a battery and a circuit configured to monitor the battery in situ. The circuit may include at least one sensor positioned to sense at least one property of the battery and a processor in communication with the sensor. The battery assembly may also include a battery housing, wherein the battery and the circuit are positioned within the battery housing. A method for evaluating a battery in an electric device. The method may include collecting operational information from the battery. The operational information may be collected without removing the battery from the electric device. The method may also include comparing the operational information to a degradation routine describing a property of the battery and calculating a capacity of the battery.