CR2032

From Sega Retro

CR2032 is a designation for a small 3-volt battery about the size of a nickel, very commonly used as the battery for supplying power to SRAM chips to prevent them from losing the stored information when the console is turned off.

It's a very popular battery and in case you ever need to replace an ailing CR2032 they're sold at most electronics stores.

Uses of the CR2032