A rechargeable battery having a built-in controller is disclosed that extends the service run time of the battery. The controller may extend the service run time of a rechargeable battery, for example, by ending the discharge cycle at the optimal discharge depth in order to maximize the number and efficiency of charge cycles. The controller may also control the charge cycle of each electrochemical cell of a rechargeable battery. The rechargeable battery may be a single-cell battery, a universal single-cell battery, a multiple-cell battery or a multiple-cell hybrid battery. Each individual cell preferably has a built-in controller that controls the discharge and charge cycles of that cell. In addition, the rechargeable battery may also include a remote charging system.