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 on Electric Vehicles From The Green Living Guy
Return of The Electric Car
Why the Lincoln MKZ Hybrid is More EV Than Hybrid?
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
More problems with this approach (applying different battery voltages, via connections, to achieve different motor speeds):a) motors do not work efficiently on different input voltages. Low voltages may burn out the motor.b) some batteries get used more than others, leading to an unbalanced state-of-charge across the battery pack as well as faster aging of some batteries. Both problems can reduce the life of the overall battery pack.c) each time the switch activates there is a chance of sparking, which destroys contactor contacts and creates more danger of a hydrogen gas explosion. Worn contacts become more resistive, which creates hot spots and limits the current available to the motor.I agree that Switch Controllers are not the best choices for electric vehicles. However, merely duplicating the switching action via vehicle wiring just moves the same problem to another place. Instead we need more sophisticated motor controllers that perform voltage level and serial/parallel manipulations using low resistance and sparkless power semiconductors.