A charging apparatus for charging a battery comprising a current source for providing current to the battery, a controller connected to the battery and to the current source for controlling charging of the battery, and a memory connected to the controller for storing information about the battery. The memory may also store information about the charging apparatus. Preferably, the memory is a nonvolatile memory, such as E.sup.2PROM. Also disclosed are a battery having a memory for storing information, a power tool having a memory for storing information about the tool, and a reading apparatus for reading the information stored in the memory of the charger, battery and/or power tool.