The processor is based on a ATmega328 micro controller connected to 20 MOSFETs and an Accelerator device. Each MOSFET switches a solenoid for 100 ms if activated by the ATmega328. The processor can put a switch in the bypass position or in the position where the battery is switched in series with the other batteries. Two solenoids are used for the two positions of each switch. The springs in the switch keep the copper cross bar in the required position after it has been activated for a 100 ms. (Therefore no excessive power dissipation in the solenoids.)

5V supply is provided via a standard 7805 regulator circuit from the 12 V vehicle utility battery.

A current sensor may be fitted, if required, to prevent over current from the batteries. The current sensor can be added to pin 27 of the processor.

The controller circuit diagram is shown in the figure below.

The program is written in Basic Language. The listing is given below.S

The program was created and compiled with BASCOM AVR and the programmer used is the USB-ISP programmer, both available from www.mcselec.com

The processor can be constructed using breadboard and installing it into an enclosure