Why shouldn't rechargeable batteries be used in the Game Boy?

Compared with disposable batteries, rechargable batteries can fail more quickly and their positive poles are shaped rather differently. This can lead to contact problems in the battery compartment, resulting in the loss of game data and causing games to crash or screens to malfunction.

Moreover, the voltage of an rechargable battery is usually only about 1.2 V. The requirement, however, is 1.5 V, so the voltage might be insufficient to run the Game Boy, or the game could be cut short.

If rechargeable batteries are nevertheless used in the Game Boy, note that they must be removed from the Game Boy before they are charged.