What kind of battery does the remote / receiver take?

The receiver of the Accessory Power Wireless Remote System takes a CR2 type battery (pictured below). It is removed by sliding off the back cover of the receiver with a finger, then removing the battery.



The remote of the Accessory Power Wireless Remote System takes a A23 type battery (pictured below). It is removed by taking off the back cover of the remote, it is held on by two small screws.