Inside of key fob

This is the inside of the key fob.

For those that haven't disassembled it, insert a thin flat-blade screwdriver into a small hole in the groove between the front and back halves very close to the panic button (at about 11 O'Clock if you hold the key fob buttons toward you, panic button at 12 O'Clock) and twist.

It uses the CR-2032 battery. The PCB is retained by the rubber button pad. Gentle pressure on the buttons on the other side will lift the button pad/PCB assembly from the front half.