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Building an electric motorcycle: what does it take to design an e-moto?

What comes to mind when someone says the words “electric motorcycle” and what defines the classification itself? It is being able to hit a minimum top speed? Or is it based on the physical size of the bike? Or is it a minimum level of acceptable power to be called a “motorcycle”? Over the course of these next few articles, we’ll do our best to answer the above questions and share the process in what goes into designing one.

The overall jist of the next few articles will cover major power train components and the design architecture that goes into a final production electric motorcycle; starting from the heart of the beast, the battery, then moving on to other key components such as the controller or inverter, electric motor, wiring and interconnect systems and finally the ECU to control the entire vehicle.

To begin the discussion, we will do our best to encompass our definition of what an electric motorcycle is. The word “motorcycle” has been thrown around in recent years when it comes to the electric variant, covering vehicles such as high power electric bicycles and underbone style electric mopeds. To understand the future of the motorcycle, the best bet is to look back in history as to what defined the motorcycle over the last 100 years.

mo·tor·cy·cle

[ˈmōdərˌsīk(ə)l]

NOUN motorcycles (plural noun)

A two-wheeled vehicle that is powered by a motor and has no pedals.

So, from the Oxford Dictionary definition, we can then rule out anything that contains pedals; bicycles, small electric scooters with pedals, etc. To explore the definition from another perspective such as the NHTSA, which is the US Government body in charge of highway traffic and safety, encompassing the certification of all vehicles which are road legal in the US, their quote is:

“Each state had different definitions of a motorcycle, scooter or moped (or motorized bicycle) using characteristics as varied as top speed capabilities, engine displacement, horsepower, wheel size, enclosures and other features.”

To define what a scooter is: a scooter is also defined as 2 wheels inline on vehicle with as step through design. Therefore anything with a step through design, such as underbone motorcycles, maxi scooters and traditional scooters are then all classified as a "scooter".

Finally, NHSTA also requires an OEM, a company that produces road worthy vehicles to issue a VIN number on the vehicle for registration. Many Chinese factories that produce electric "motorcycles" and electric scooters do not have a VIN number that conforms to WMI (World Manufacturer Identifier) standards. They are sold as "off-road" use or sold to their customers awaiting a VIN number, thereby stranding resellers and distributors with product, but without a means to get them street-legal.

So, to generalize and summarize the above information, what defines a motorcycle, it that it is a 2 wheeled vehicle, with both its wheels inline, without pedals, that reach a minimum top speed of around 70km/h, with a power rating of 150cc+ equivalent or around 6 brake horsepower, that is not a step through design, manufactured by a company that can issue VIN numbers for road certification.

Now, when it comes to electric, the big question is how to equate the power output, measured in watts or kilowatts to an equivalent engine displacement, measured in cubic centimeters, cubic inches or litres. Additionally, we will need to look at the governing bodies and insurance companies on how they will classify electric motorcycles as they gain more popularity.

Our next article will cover what it takes to design and manufacture battery packs for electric motorcycle applications; high C discharge, wide temperature applications, and stability in the pack to classify it as a true electric motorcycle power source.

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