Perko Compact 1-2-All Battery Switch The Perko 8511 Battery Selector Switch is a compact and durable battery switch that has a bright red polycarbonate housing with a large easy-to-turn black knob. The Perko Compact Battery Selector Switch has a number of functions its allows for a quick and easy way to shut down the entire electrical system in an emergency this device also permits battery selection of two or more batteries for specific purposes, including starting engines, running accessories