Electric conversion of a 1984 Honda CM450

[harrisonpatm]

I was attracted to YouTube videos of electric motorcycle conversions and I kept thinking that it seemed doable, even for my inexperienced talents. So when I came across an old Honda with a dead engine going for $150, I went for it. This was mid-May of this year, about 4 months ago.



Engine was dead, but that didn't matter, and frame was good. I stripped it to pieces, which was my first pleasant surprise, because I was actually able to do it completely in one day by myself with no specialty tools. That's when I got confident and started ordering parts, and taking night classes at YouTube university to brush up on all the skills I would need.

-QS273 8000W-continuous-rated hub motor on an 16-in rim, Kenda Challenger tire
-APT96600 400 amp BLDC motor controller. It has its pros and cons, but mostly I got it because it came with the motor and I had to start somewhere. It's not terrible, but I'll find a different one for the next conversion.



-Battery! I wanted to go LiFePO4, even though it's heavier than Li-Ion, because I'm not an experienced rider and I went for safety, longevity, and temp range (I live in Michigan and might be using this in late fall and early spring) over weight and power. Went with 32650s from Battery Hookup, 12p24s to get that 72v range, just over 5kwh. I picked a JKBMS 200A for it's price point and relatively good reviews online. Daly was another option, but much pricier. We'll see if this one lasts. Battery weight with cables and everything was about 110 pounds, still lighter than the engine was. I don't weld, so I found a welder who was able to make an aluminum case for it that mounted to the frame in the same spot the engine was. If the brackets held the 175-lb engine, they'll hold the battery just fine.




I use a 400-amp contactor, a 200-amp shunt to read amperage off the battery during riding, and a 350-amp breaker for the power train cabling. BMS rated for 200 amps continuous, the controller is rated for 600 amps, the motor is rated for about 130 amps continuous and 250 amps peak... I should be good. Spoiler alert, it does run, but I would love feedback from the forum on how well I selected, rated and built all my components. Who wants to place bets on which component fails first?!?

I cut the bottom of the fuel tank to make room for electronics. Then when the controller arrived, much larger than expected, I cut a hole out of the top as well. Oh well.


For charging, I don't actually have an AC charger yet, but it is planned, either purchase or assemble. For now, I set up 2ea 240w solar panls on the south side of my house. Series connected for now, at about 66Voc, connected to the MPT-7210 boost charge converter to bump it to motorcycle battery voltage. This gives me 4-8 amps at a time, which means I can fully charge the battery in about 10-14 hours of direct sunlight (2-3 days?) This is totally fine for now, I'm not riding miles every day, don't need to charge it every day. This is just going to be my commuter to work 2-3 miles a day, plus joy riding. My future upgrade plan is to upgrade my house's small off-grid battery bank to 48V and use a proper, better, true MPPT controller to collect sunlight at all times, not just when I have the bike plugged in. Then I can treat that as my bike's reservoir, and use a boost converter to tap into the 48V bank to charge my 72v bike; faster, more regularly (better for long-term battery life), and more convenient.

I could go into a lot more details on every little thing, but I'll let pictures speak for themselves. Let me know if you have any comments or feedback. I also have plenty more to do. Namely, need to find a better way to cover up the controller. If anyone is thinking about doing it, I say go for it. This was a surprisingly achievable project.


P.S. The biggest mistake I made was picking a relatively heavy bike. Next time, I'm going smaller and lighter. Smaller battery needed, smaller motor, smaller controller, cheaper, ect...

Checking out the competition...

 

[LewTwo]

Nice work :thumb: :thumb: :thumb:

 

[Grautuefel]

Dude, thats awesome

 

[harrisonpatm]

Sorry guys, I'm a new member and I'm now seeing that this post belongs in the E-scooter/E-Motorcycle section, not ebike. Perhaps a moderator could move it?

 

[harrisonpatm]

Couple months of use, and I wanted to update, for anyone else referencing the post for their own builds. I commute 5 miles round trip every day. So far I'm still limited to direct solar charging, which is a lovely idea in concept but means I'm highly dependent on the weather if I want to plan a longer outing. I've ordered an AC charger to remedy that, and I am still slowly working on the stationary solar backup battery in my free time. Then I'll have a proper solar-powered motorcycle that I can charge much more regularly and conveniently.

The 32650 cells I picked were perfectly ok, but next time I will try to find something that can handle higher discharge rates without voltage sag. Under normal driving conditions, I see on my panel mounted voltmeter a sag of around 2-3 percent. This goes up to 4-5 percent sag when I have to accelerate to 60-80kmh. Then when I really have to floor it, to overcome traffic or go up a steep hill, I see an 8-10 percent sag. The voltage always rebounds back up easily enough, and I rarely have to pull the full 200-300 amps to make it happen, but in a perfect world, I'd rather not have that much sag.

Top cruising speed, easily maintained without stressing the battery, is 50-55mph no problem. I can use the boost mode to get up to 65-70 for short periods of time, as long as I keep them short. Range on a full charge is 45-55 miles depending on how hard and fast I'm going. Bike weight is about 350 pounds, I weigh 200.

One more ask, would a moderator possibly be able to move this post to the E-Motorcycle Builds thread? I mistakenly posted in the wrong section as a newbie, and I have since learned the error of my ways, but I don't think I can move the post over myself.
Edit: Thank you!

 

[SlowCo]

Great build :thumb:

 

[mazzola]

Nice! Did you have to modify your swingarm at all to fit the QS motor? And how was the process of swapping out the rear drum brake for a disc brake?

 

[harrisonpatm]

Nice! Did you have to modify your swingarm at all to fit the QS motor?

Not much. A slot gets cut out of the back so qs273 can slide in without removing the axle. The original axle is bigger than the qs273 by 1-2mm, so I made a couple shims to keep the axle from moving vertically within the swingarm. I did not bend the swingarm, but I did use about 3-8mm worth of spacers, also provided by qsmotor. I used the qs-provided torque arms, tightened the axle closed with a lock washers, then drilled through the nut and the axle to insert cotter pins on both sides. I have had zero loosening or spinout.

And how was the process of swapping out the rear drum brake for a disc brake?

Not well enough that I would recommend what i did. You can purchase disc brake calipers and adapters that fit your axle size. And use the torque bar from the drum brake to fix it relative to the axle. It technical works on my setup, but not great; you can only expect so much from slapping on aftermarket parts. On the plus side, I rarely use it. I've had several emergency stop from 50mph, and I did them with the original front drum brake. Plus I have regen braking from the rear wheel. So I don't miss the rear brake, but if I did it again, I'd find a rear swingarm that already has rear disc brakes on it.

If you look into the physics of motorcycle riding, the front wheel does the majority of stopping power anyway.

 

[mazzola]

I used the qs-provided torque arms, tightened the axle closed with a lock washers, then drilled through the nut and the axle to insert cotter pins on both sides.

Nice, yeah I'd want to use a cotter pin just like my CB550 stock axle did to prevent loosening.

I'm thinking of using regen for rear wheel breaking as well - it seems like it would do just as good of a job as the old drum brakes (without the maintenance) and also like you said, braking power overwhelmingly comes from the front brake.

What do you have the regen hooked up to? The old rear brake pedal or something on the handlebars?

 

[harrisonpatm]

What do you have the regen hooked up to? The old rear brake pedal or something on the handlebars?

I got the apt96600, and it has an automatic regen function. When i roll back on the throttle, regen engages. No input from me needed. I messed with the settings until I found an amount of rear wheel braking that would bring me to a stop at a red light or stop sign, gently but firmly. I said that I rarely use the rear disc brake? I also don't even use the front brake much, only when finishing a stop or in an emergency.

My controller may or may not have variable regen capability, I'm not sure, it was difficult to figure out. But I've found that I don't feel I need it in my case, so I stopped worrying about it.