IT IS RECOMMENDED TO HAVE ANOTHER PERSON WITH YOU TO HELP WITH THIS STEP

Now that the parity battery is attached, it's time to remove the old battery that we'll be replacing.

Grab a flat head screwdriver in place it underneath the battery on the other side of the PCB. Now start carefully heating up the solder on one of the main batteries terminals. While melting the solder, use the screwdriver to carefully push the battery out from the board using the screwdriver as a lever.

Eventually, the battery should come loose and the pin should fall from the PCB easily, given you're providing enough pushing force with the screwdriver.

Follow the same method for removing the other pin from the PCB. This time however, you can pull the battery out while melting the solder rather than using the screwdriver to lever the battery out.

Just to be sure, use your Multimeter to test the main battery terminals after you've removed the old battery and check that there's still electricity running through the circuit. If you get a stable voltage reading from the main battery terminals (circled Red in step 5) after you've removed the old battery, then your save game is still safe.