To see the controller operate, play this video. (save link as…)
The controller is based on using 10 x 12V batteries in series, each fitted with an Electro-mechanical switch, which is able to bypass a battery or switch it in series with other batteries and the motor. The batteries, switches and motor is connected to each other using thick copper cable. Copper cable is available from this company: https://directcable.co.za/collections/welding-cable/products/50mm-welding-cable. The photo below shows such an electro-mechanical switch fitted on top of a 12 V battery.
Play this presentation which illustrates the concept for the electromechanical switch controller.
The concept is further described in the figure below.
NB: Batteries are switched in or out (in series) depending on the accelerator value. The processor (ATmega8) also adjusts the starting point of the battery bank every 15 seconds (move on by one battery) in order to ensure that all batteries perform the same work over time.
The accelerator is a linear slide potentiometer connected to the original petrol cable of the vehicle. A spring is used to return the slider to zero when no acceleration is required. (See photo below).