Once upon a time, a long, long time ago, you needed to put an actual key into a car's door lock to get in. Today, the doors of most modern cars are unlocked by pressing a button on the key.

Of course, all hope is not lost because this usually just means the battery in your key fob has died and needs to be replaced. And there's no need for a trip to the dealership to do it as it’s ...

the first step was to disassemble the already broken key fob and separate out the PCB from the case and battery holder. With those removed, a coin cell was soldered to some wires connected to the PCB.