The DateTrikE goes Electric

When the DateTrike made its debut ten years ago, electric bikes were still just a curiosity. But times change, technology advances, and today e-bikes are the rage. I have been considering adding some electric assist for awhile now. I’m not as young as I was ten years ago, and the hills are just as steep. I replaced the rear tires recently and noticed that the tire on my side had considerably more wear than the tire on the side that Ellen pedals. I’m just stronger, so on those up-hills I’m putting more power into the propulsion, and for a loaded heavy craft, that puts strain on the knees. (With a recumbent and your back against the seat, you have the ability to push very hard.) Electric assist would make the hills easier, give us more range for the typical joy ride, save the knees, and would be just plain fun!

I considered various options for where to put the motor, but by far the simplest was a hub motor for the front wheel. This has the advantage that the bike now becomes “three-wheel-drive”, with the front wheel powered by the motor and each passenger pedaling their own rear wheel. We will never get stuck in the playa sand at Burning Man with three wheel drive. The front hub motor is also standard fare for motorizing regular bikes so the motors and kits are readily available.

After some consideration, I went with Grin Technologies components. Grin has been around since before e-bikes were popular and they specialize in kits and retrofits with innovative and high quality products. I purchased a Nine-Continent front hub motor from them along with the Grin Baserunner controller and the Cycle Analyst display. The components work together with lots of options for throttles, pedal assist sensors, regenerative braking, battery monitoring, etc. I was especially eager to incorporate regenerative braking because the trike was a bit under powered in the brake department. The two rear disc brakes work well enough, but there was no front brake. Front wheels can exert much more braking force than can the rear wheels.

I selected a battery on e-bay from China that appeared to have sufficient capacity with a form factor that might fit under the rear deck of the trike. It turned out to just fit in a pocket next to the left-side chain and gears.

The battery is a 48V Li-ion type with a claimed capacity of 20 AH, weighs 8.4 lbs, and is good for 1000W motors. I suspect it is actually closer to 16 AH, but still seems to be able to provide an adequate range for our needs, perhaps 40+ miles.

The motor is controlled by a thumb-activated throttle located on the steering tiller. In addition I added a magnetic sensor to the brake lever to activate the regenerative electric brake on the front wheel. The Cycle Analyst display mounted to the trike frame shows the battery charge state, motor power, motor temperature, speed and trip mileage. It also keeps track of battery performance and life and total mileage as long as the device is reset after every battery recharge.

The new front wheel replaced the hub generator previously employed to power the head and tail lights. I replaced the front headlight with one designed to run off of the 48V e-bike battery. I also added 12V DC-DC converter to run the tail lights and other 12V decorative lights.

With everything installed and working, the DateTrikE has proven to be a real joy. In the summer, with the canopy up, we can still make good headway along the paths without wearing ourselves out completely. I’ve capped the speed in the controller at about 15 mph, which is plenty fast for the trike along the bike paths, and allows our pedaling to still provide a significant fraction of our power. The regenerative braking is especially nice on the trike. Just lightly pulling on the brake lever, without engaging the rear disc brakes, turns on the regeneration and starts to slow the trike with the front wheel. With the brakes engaged, increasing the thumb throttle increases the electric braking power if you want to stop faster. Using the front wheel for braking reduces the back-and-forth stress on the drive train and moves it to the front. This seems to help keep the wheel nuts tight in the rear, we will see if it moves the issue to the front wheel.

The last trip incorporated a steep hill climb and total distance of about 25 miles, which was a very pleasant outing. We are looking forward to many more excursions this summer, ranging further and with more daring rides up bigger hills than in the past.