Acorn Master 128 - Battery maintenance

The Battery warning label on a BBC Master 128

The Master series originally came with a three AA battery pack although was designed to be able to charge a battery if required. These days, you can still fit a three battery solution or you can fit a single Lithium battery again with suitable diode (BAT42 or 1N4001)/resistor (120 ohm) combination to prevent back charging and limit current in the event of diode failure.

RetroClinic Lithium battery for Acorn Master series

The Lithium batteries theoretically should live for around 10 years but it is recommended to replace them once every 3 or 4 years and the full kits are available from RetroClinic.