I’ve always loved vintage conversions to electric power. Dan is located in Kansas, and one day he showed his wife some pictures of motorcycles to see what kind she likes, and they settled on a vintage Honda from this era. It didn’t take long for him to find one in decent shape with a seized engine for only $500. I’ve also heard of builders buying an example that was running, and then selling the engine and transmission to someone who is restoring one, for near the cost of the entire purchase.
This particular model is a 160cc “Baby Dream” (made between 1966-69), and Dan has decided to call it the Dream-E.
In the pic above, Dan has stripped the frame down quite a bit (you can see the front wheel on the floor in the background). I love the style of the classic “toaster” gas tank, which Dan made sure to keep. You can also see how Honda made the frame out of two halves of pressed sheet-metal, rather than the common welded cylindrical tubes. Doing it this way can be lighter and more affordable to produce. If you ever want to search for something similar, make absolutely certain that the frame is not damaged by deep rust. However, mild dents and paint are not a problem, as you will soon see below.
Another benefit of this style of frame is that the engine is a stressed member, so there is no downtube curving under the engine. Any battery box that might be mounted in this space will also have to “hang” from the top and rear, but there are no frame-members that will interfere with the size and shape of the battery box.
Now that Dan had the frame in-hand, he can take measurements on the swingarm spacing, and order the motor that he has selected.
Dan used a paint-removal disc on a power tool to get everything down to bare metal. Some dings were pounded out, and others were filled with Bondo, and sanded smooth.
The hollow fork-arms conceal coil-springs that provide roughly five inches of travel.
Before Dan can think about paint, he will have to modify the swingarm axle-slots to accept a hubmotor axle. He will also need to widen the mounting slot location to fit the axle shoulders of the 4,000W QS motor (more on that farther below)
In the pic above, you can see that the swingarm is also made of hollow pressed sheet-metal halves, and each arm has dozens of spot-welds to connect both sides of each. There is a solid steel plate inside the swingarm at the axle drop-outs and shock absorber mounts, to strengthen that area.
Stripping all the paint doesn’t just provide a smooth base for a new paint-job, it also allowed Dan to inspect all of the sheet-metal for deep rust pits, which would have to be repaired to avoid any weak spots.
I’ve been calling the material “sheet-metal” but, be aware it is fairly thick 16-ga steel sheet.
In the pic above, you can see one of the new custom drop-outs welded into place. Not only are they much stronger than the stock axle-mounts, they are located on the outside of the swingarm to spread them farther apart, due to the width of the hubmotor’s axle-shoulders.
The stock chain-drive did not apply twisting forces to the rear axle, but the new hubmotor will definitely try to twist in the opposite direction as the rear wheel. It is vital to use two strong torque-arms when using a hubmotor.
Dan chose the Quan Shun / QS 4000W “10 x 2.15-inch” hubmotor (click here), and specified the model that takes spokes instead of the solid cast aluminum wheel/motor. The stator size is 205/55H.
Mounting the Controller
The QS motor website listed several controllers that would work with the hubmotor that Dan selected, and he chose the Kelly sine-wave KLS7245N. Voltage is 72V nominal (20 lithium cells in series / 20S), and when fully-charged at 4.1V per cell, the battery would rest at 82V. Kelly lists the max volts as 90V, so there is roughly 8 volts of safety margin to deal with voltage spikes.
This model is rated for 100A continuous, and 350A as a temporary peak. 72V x 100A = 7200 Watts, and 72V x 350A is 25,000W (25-kW). Since Dan’s battery can only output 60A, this controller and motor should run relatively cool, and last a very long time. 72V x 60A = 4300-watts.
The Kelly Controller (KLS7245N)
This controller can be programmed with a PC laptop via USB, and a wireless Bluetooth module can be added at the time of ordering for a fee. It also has an electronic reverse function, which can be handy if you need to back up the motorcycle.
In the pic above you can see that the “top” of the controller is inside the hollow body of the frame, and the aluminum fins on the baseplate are exposed to help with cooling. This space in the center of the frame was normally used to house the stock 6V lead-acid starter battery, and the air-filter. Dan cut the opening to fit the controller, as shown.
As soon as Dan had stripped the old paint off of the frame and smoothed-out the dings, he sealed it with gray primer to keep rust away until he is ready for paint.
Small converters that take the pack voltage and provide 12V are very common, and you need to size them to provide the amount of amps you expect to use. Dan is upgrading the headlight from 6V to 12V, and since he will be using a modern low-watt LED bulb, the amp-draw will be modest, allowing for a fairly small converter.
Dan wanted to keep the stock look, so for paint he used single-stage 2K urethane from Eastwood. The color is “Interstate Black”.
Dan ended up using three coats of paint. Then the paint was wet-sanded smooth. First the 600 grit, then 1500, and on the final sanding he used 2000-grit. At the end, he gently power-buffed the urethane to a smooth shine.
The motorcycle originally came with a long flat double-seat. Dan found a solo seat that he liked (at a motorcycle swap-meet) and then he modified a cheap universal rack to fit.
One of the most exciting days in a restoration is when you can start re-assembling the finished pieces. In the pic above you can see the new solo seat, the re-chromed trim, and the new 16-inch street tires.
The stock rear wheel had an internal drum brake, but the QS motor comes with a disc brake, so Dan fabricated a steel disc caliper mount. The pads should last a very long time, because the controller has a regenerative braking feature (regen), which converts the hub-motor to a magnetic brake when slowing down.
The Battery Pack
Within the space that Dan had available, he decided to use high-amp LG-Chem cells from a salvaged EV. These flat pouch cells are 11-inches by 9.5-inches (280mm x 241mm). Forty of them were $200 with $50 in shipping added. They were purchased from Battery Hookup in Bensalem, Pennsylvania.
To get 72V nominal, the pack would use 20 lithium cells in series (20S). This build had room for two blocks of 20, so the pack uses two cells in parallel (2P). Each cell was 15-Ah in capacity when it was new, so a 2P configuration of fairly new cells would be 30-Ah of range.
Dan estimates that these particular cells are at roughly 2/3rds capacity, and as such would only provide 60A in a 2P configuration, with 20-Ah of range. They arrived in 4-cell bundles, so Dan had to cut them all apart and reattach them in 20S / 2P.
LG-Chem is located in South Korea, and as president Yoon Suk-Yeol always says “South Korea is best Korea”
The finished pack, with electrically-insulating Kapton tape, and some white wrap.
The original engine and transmission were roughly 80-lbs, so the 60-lb battery pack is a definite improvement.
The Battery Box
Dan chose 20-ga sheet steel to form the battery box. He has the tools and experience to cut and form these materials, so he could create a custom enclosure that ended up being a really impressive result.
The black and red connectors at the base of the housing are “Dinse” 200A TIG-welding connectors.
The Final Assembly
Dan trimmed and attached each wire very carefully, so everything would work correctly right away. There is a kill switch on the handlebars, and a large DC main contactor mounted inside the center of the frame.
The video above shows Dan programming the Kelly controller, and I included this because it is the most mystifying part of a new electric conversion build, and I thought readers would find it helpful.
Dan stated that the completed Dream-E accelerates harder than his gasoline 200cc motorcycle. He built it for his wife, who was willing to ride with him, but wanted her own motorcycle, as long as it didn’t require shifting or operating a clutch. The current top-speed is 55-MPH (88 km/h).
I think this project is beautiful, and its functionality is exceptional. Of course it rides almost silently, and it does not require oil changes, or chain adjustment and lubrication. Don’t crush vintage classics for scrap-metal, convert them!
Written by Ron/spinningmagnets, December 2022