Abstract: A method for determining the maximum capacity a battery to store charge for the benefit of state of charge and state of health determinations, otherwise known as the maximum capacity estimator, is described. In an embodiment, a memory storage unit is used to collect input data from a battery or battery pack over the life cycle of the battery. As the battery operates, discharge cycles are analyzed to determine the similarity between different cycles throughout the operational phase. The maximum capacity at a given time for storing charge is then determined by comparing the trend of capacity loss in similar cycles and then applying that trend to the reduction of the maximum capacity of the battery. This method allows state of health and state of charge measurements to be made and updated with respect to battery degradation without the need for scheduled maintenance checks-ups such as mandatory discharge cycles or impedance/resistance measurements.