Desoldering tools are great for cleaning up mistakes. They're really easy to use!

Apply a copious amount of solder to the battery pad, as explained in the previous step. [photo with copious solder, iron, and desoldering tool in play]

Depress the plunger in the desoldering tool until it clicks.

Heat up the joint until the solder flows.

Press the tip of the desoldering tool into the pool of solder. Simultaneously press the return button on the tool.

Whoop! Away goes the solder! Press the plunger down again to release the solder it collected. [photo with iron and desoldering tool in play, solder gone]