Here's how:

• Unlock the Padlock E and pull the shackle to the open position.
• Turn the Torx cap clockwise 90° with the Torx Screwdriver & pull the battery cover out.
• Replace the CR2 Battery, close the battery cover, and turn the Torx cap counter-clockwise 90°.
• Push the shackle to close position and ensure that the battery markings are aligned.

The following video provides a visual reference to how this is done!