Whenever your Yamaha keyboard begins to show a low battery message, or is not saving the internal memory data as it should, it is probably time to replace the internal battery. Even though your keyboard is AC powered, the internal battery is responsible for keeping settings and configurations saved while the power is off. If you haven't ever replaced the lithium coin battery in your Yamaha keyboard before, don't worry. With the right instruction, you can exchange it for a new one in less than an hour.
Unplug the keyboard's power cable from the wall outlet and turn the instrument face down. This will expose the housing screws that need to be taken out to access the battery compartment.
Use the Phillips screwdriver to remove all of the housing screws, then carefully remove the lower casing. Be careful, for many Yamaha keyboards have wires that connect the two panels together. Carefully set it aside so that you are able to reach the battery.
Locate the round, coin-shaped lithium battery and pull it from its compartment. The battery compartment will be located on the circuit board.
Insert the new battery with the positive (+) side facing up, then replace the casing and housing screws. Once the keyboard is powered on again, the new internal battery will be functional.
Lithium coin batteries in keyboards should be replaced every five years.