A battery pack in one aspect of the present disclosure includes a rechargeable battery, a rewritable nonvolatile memory, a write request receiver, and a write controller. The rewritable nonvolatile memory includes storage areas including a write-inhibit area. The write request receiver receives a write request and data from a charger. The write request includes a first address assigned to a first storage area of the storage areas. The data includes a first data element. The write controller executes a write process for the received data. The write process includes avoiding writing the first data element to the first storage area in response to determining that the first storage area is the write-inhibit area.