Electric Midget Wiring Diagram

 

 I wanted to post this diagram because I realized a good wiring diagram could explain a lot of things to people considering doing their own conversion. So in a basic wiring diagram you’ll see the main battery pack, a battery to supply 12 volts, the controller, a DC-DC converter, a start switch, a charger, and a throttle. In my diagram I added the BMS, and that complicates the wiring to some degree. The Elithion BMS needs separate 12-volt supply, one for when it controls the charging, and another driving. That is the way it knows what you want it to do. I have a separate 12-volt power supply that I plug in at the same time I plug in the charger. It supplies the 12 volts to the BMS during charging, and trickle charges my motorcycle battery at the same time. I have a diode to isolate the battery from the 12-volt supply when the supply is off. That is protection against a possible leak current that might drain the motorcycle battery. There is a relay (SW3) that supplies the BMS with its power. It is a requirement of the BMS that it’s supply is turned off quickly. If it were driven just by the 12-volt power supply, the voltage would drop too slowly when I unplugged the supply. There is another relay (SW4) that the BMS uses to turn the charger on and off. I haven’t shown the two current sensors that the BMS uses to simplify the diagram. One measures the high currents during driving, and one measures the lower currents during charging. I show a shunt in the circuit. It is used to drive a dash ammeter. I have a custom fuel gauge drive circuit that converts the BMS SOC analog voltage to the correct voltage to make my stock fuel gauge tell me how much battery I have left. The contactor (SW2) is the main on off switch. Almost all electric cars will have one. The Soliton Jr. controller has it’s own contactor built in. I added this second one so I could disconnect the DC-DC converter when the car was off. There is a fuse in the circuit to protect from direct shorts. I took special care in my wiring to make sure that when the car was off, there was no chance of a small current leak coming out of my main pack, or my small motorcycle battery. This meant adding a solenoid on the output of my DC-DC converter as well as the input.

Please contact me if you have questions about the wiring, I’ll be glad to answer them.

Wiring diagram for the electric mg midget