AC Delco D1876D Inertia Switch

An Inertia Switch is an important safety device on any electric vehicle. In the event of a collision, internal combustion engines usually stop, either by strain stalling the engine or a breach in the fuel supply. Most cars are actually protected by an inertia switch that disables the fuel pump. In an electric car, this can be even more important. If the driver is incompacitated with weight on the accelerator and no load on the wheels the motor can spin uncontrollably until it reaches past maximum RPM and dissassembles itself explosively. The intertia switch is a simple device that in the event of a jar or collision moves a magnetic ball out of its place and so opens the switch. By connecting this between a contactor and its ground, the contactor will automatically open on any collision, disconnecting your high voltage battery pack. If it is a minor collision, you can simply press the red rubber stopper on top to reseat the ball and again enable your system.