1. An apparatus for charging a battery, the apparatus comprising: a. an interface for electrical coupling to the battery; b. circuitry for concurrently measuring battery voltage and current; c. a database for accumulating battery parameter data from a plurality of batteries; and d. a processor for recursively updating data characterizing a model representing the battery based both on jointly measured battery voltage and current and accumulated parameter data received from the database; and e. a current supply for supplying current for charging the battery as governed by the processor.