As with choosing the motorcycle, I don’t have a formula to offer for choosing components. But I can tell you how I made my decisions.
I was initially fascinated with the hubmotor concept, which would seem to offer the ultimate in efficiency, simplicity, quiet operation, and extra room for batteries in the frame. But the more I read, the more I discovered it would come at a high price and might not deliver what I hoped for.
At the time I did my research (2014), the primary manufacturer of motorcycle hubmotors was Enertrac. Their reputation for service was excellent. The initial cost was high, but included integration of the wheel, disc brake and swingarm.
Many critics of the hubmotor concept cite unsprung weight as a concern. My reading did not reveal that this was a problem for the people actually using the motor. The issues that I read about included “cogging” (a ratcheting noise) during acceleration from a stop when using the recommended controller, and overheating. Both issues seem to be worst with the heaviest bikes at the lowest speeds.
The fix for the cogging issue appears to be upgrading to a Sevcon controller, which could be difficult to program. The fix for the overheating issue is using Enertrac’s upgraded hubmotor which is plumbed for liquid cooling. Then, integrating a cooling system onto the bike (pump, radiator, lines and fluid) to cool the motor. My vision of ultimate simplicity was beginning to fade.
Also, to get highway speeds, I would need a 96V+ system for the hubmotor, while a standard design would require 72V+. There is some efficiency in higher voltage designs, however it comes at a cost in batteries, increases the number of cells that need monitoring, and drives up the cost of other components which must be designed to handle the high voltage.
So, the desire for low cost and simplicity ended up driving me back to a standard design. The decision was clinched when I discovered that Nissan Leaf batteries could deliver the energy and power density I needed at half the cost of LiFePO4. I could fit a 84V Leaf pack without overburdening in weight, but if I tried to squeeze in two or three more modules to reach hubmotor voltage, I would run out of room and also increase weight and worsen the heating problem. In the end, the low cost of the Leaf modules drove my design.
From there, the decisions were easy. I used a proven combination that many others were using, the ME1003 and AXE7245. The decision to buy a used QuiQ-dci was based on the availability of the pannier for mounting, and the attraction of having the DC/DC converter solution already integrated for me.
The only mistake I made in selecting components was the Albright contactor. I realized my mistake as soon as I held that enormous brick in my hand. It is ideal for a forklift, not a motorcycle. I should have bought a EV200 or GV200 with 12V coil, but my misunderstanding of the controller manual (discussed in the contactor page) led me to go with the standard contactor offered with the EVDrives package.
So, that’s how I did it. You can be more systematic about your choices if you want, but if you read Vogel’s Build Your Own Electric Motorcycle and start doing computations for rolling friction and drag, you may get overwhelmed. I highly recommend reading what others have done. Your performance will come out much like the other designs with the same components, weight, and sprocket ratio.
Read, read, read. I read for four months before I ordered my components. The time invested in reading will pay off. Don’t go on the ElMoto forum after two days of reading and start asking questions. Read first, the answers are already there. Save your questions for particular details in which you need help from the experts. If you read interesting threads just for fun, you will be surprised to discover key information that you can apply to your project. Read, read, read. Then steal the best design!
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