As I wrote in Build Your Own Electric Vehicle, 2nd Edition, a switch controller is the oldest type of controller for an electric car. They’ve been used for over 100 years and there are still lots of them in use today. Basically, they are a set of big switches that connect the batteries and motor(s) in various series/parallel combinations to get discrete speeds.
For example, four 12 volt batteries could be connected for 12, 24 or 48 volts to provide slow, medium and fast motor speeds. Switch controllers are cheap, simple, and efficient.
However, their main drawbacks are the stepwise speed control and minimal feature settings.
Bottom line. you don’t generally buy a controlller like this. Instead you buy the parts and wire the vehicle yourself according to a basic wiring diagram (like when an electrician wires a new room in your house).
More from The Green Living Guy:
1. Build Your Own Electric Vehicle by Seth Leitman and Bob Brandt
2. Build Your Own Plug-in Hybrid Electric Vehicle by Seth Leitman
3. Build Your Own Electric Motorcycle by Carl Vogel