Pokémon Crystal Version/Battery Life

Copies of the Generation II games typically lose the ability to save in a shorter timeframe than copies of the Generation I games due to the battery maintaining both the saved game and real-time clock data, causing it to drain quicker.

The battery is replaceable with another one of the same kind (a CR2025), or a, which is slightly thicker and lasts longer. Since it powers the save file, interrupting the power by removing the battery will cause any current save file to be lost. Third party devices such as the GameShark may offer ways to backup and restore the save file.

A symptom of a battery running dry is the game's inability to keep track of the time correctly (the error message TIME NOT SET may also appear on the title screen).