The battery is wired to a multi connector which also has wires to the speaker and charging socket. It's not possible to separate the battery wires from this connector without a special tool and an unnecessary amount of bother.

So we'll snip the battery wires to remove the battery and join our new battery onto those later.

Be sure to cut the wires one at a time so you don't cause a short-circuit.

It's best to cut them close to the battery so you have a decent amount of wire still attached to the main Minirig body.