The power-management IC used on Raspberry Pi 5 integrates a real-time clock, and charging circuitry for a button cell which can power the clock while main power is disconnected. This Panasonic ML-2020 Lithium Manganese Dioxide battery, with a two-pin plug is suitable for connection to the battery connector on the Raspberry Pi 5 board. A double-sided adhesive pad can be used to attach the battery to the inside of a case or another convenient location.