A method and apparatus for controlling access to one or more memories in a rechargeable battery includes a switching circuit that connects the memory to a device data contact, and disconnects the memory from a charger data contact, when the rechargeable battery is connected only to a device powered by a battery. The switching circuit, however, connects the memory to the charger data contact and disconnects it from the device data contact. In some embodiments a second memory that contains a subset of the data in the first memory is connected to the device data contact when the first memory is connected to the charger data contact.