Abstract: A battery having a built-in controller that controls one or more functions of the battery is disclosed. The battery may, for example, control a charge or a discharge cycle of a battery, disconnect an electrochemical cell from the terminals of the battery in an emergency condition, provide electronic identification of all characteristics or conditions, or provide a low remaining charge warning. The 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.