Press the soldering tip to the 3 connection points to detach the motherboard and the battery. See this guide for information and tips on soldering and desoldering.

You will need to reattach these connection points when reassembling your device with the soldering iron. This guide will walk you through how to do that. Be sure to attach the positive and negative wires to the correct connections.

Exercise caution when desoldering the battery, especially if you've had issues with the device's power which could point to it being faulty. Consider using an anti-static wrist strap when working with the battery and its cables. See this guide for information on swollen batteries, another thing to look out for.

The battery is now disconnected and ready to be replaced.