Insert the flat edge of a spudger underneath one short edge of the battery.

Push the spudger underneath the battery, separating it from the adhesive holding it to the keyboard.

Make sure you push underneath the battery and not into it. Don't bend or deform the battery.

Remove the battery.

To install a replacement battery:

Remove any leftover adhesive from the battery well.

Apply double sided tape or pre-cut adhesive to secure the new battery.