1976 Harley Electric Edition

Check out this unique conversion. A 1976 AMF Harley Davidson ss175 motorcycle left outside, uncared for and robbed for parts. Water was making its way down the open cylinder head and into the lower crank case when I purchased it. It’s been given a new lease on life, touting an 8000-watt electric motor powered by a 72-volt lithium-ion battery back. This motorcycle is once again cruising the streets in electric style!

Wiring

After stripping down the motorcycle to the frame and giving it a good wash, it was put back together with all new wiring and LED lights. Low power components were carefully selected to maximize the battery life. A DC-to-DC converter steps down the 72-volt battery pack to 12 volts to operate the lights and other components eliminating the need for an additional power source.

Battery Pack

Being limited by space, I had to build my own custom battery pack small enough to fit where the gas engine once resided while being powerful enough to safely discharge over 12000 watts! Even though the motor is only 8000 watts, in actuality during acceleration and heavy loads it uses over 1.5x this amount (12000-14000 watts).

I had to use lithium-ion cells rated for high discharge. I choose the Samsung 40T3 21700 4000mAh cells. These lithium-ion batteries are rated at 3.6 volts and have a true Contant Discharge Rating of 35 amps without involving a temperature limit cutoff. That means one of these cells alone can output 3.6V x 35A = 126 watts. Although I needed 72 volts to run the motor, so I had to connect 20 of these together using series connections to make 3.6V x 20 = 72 volts. This outputs 72V * 35A = 2520 watts. Still not enough! I needed 5 times this amount. 2520 watts * 5 = 12,600 watts.

To achieve this, I needed a total of 100 cells in order to make 5 sets of these 20-cell 72-volt battery packs. All 5 sets were connected together using parallel connections. The final result is a 100-cell 20s5p battery pack: a 72-volt battery pack that can safely discharge 12,600 watts to operate my 8000-watt electric motor!