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

The subtle science of user experience (UX)

When we talk about user experience, usually the first thing that comes to mind is the reference to creating an app. Where the buttons are placed, where the menu is, how many clicks it takes to get something done, etc. (I can't really attest to what UX and UI are on an app). When it comes to designing an electric motorcycle digital instrumentation clusters and panels falls in line with the app guys when it comes to the UI / UX. Crucial questions such as where to put the speedometer, text visibility in sunlight and in low light, general layout, etc. From a different point of view on user experience, motor and power controllers have a wide array of programming settings capable of completely changing the way a vehicle moves, accelerates and brakes. How does the OEM balance power output and component reliability over a 10-year lifespan? These are the questions that plague electric motorcycle manufacturers daily. Our goal is to manufacture and design an amazing product from the customers perspective while balancing longevity and reliability over the product’s lifetime.

Having just wrapped up the previous article on what goes into developing a battery pack for an e-motorcycle, the area that we did not focus too heavily on the balance between range (or pack performance, aka capacity) and longevity. As all battery pack designers know, keeping charge voltages lower on the string and pack level of any lithium based cell allows for an exponential increase in cycle counts at the expense of maximum capacity.

For less upstanding battery pack suppliers or electric vehicle manufacturers, this isn’t a major issue, since their job is to squeeze as much capacity possible for the amount paid per cell, so that they can market their packs or vehicles get XX amount of range per charge, not taking into effect lifespan. Add to the fact that they pay little attention to heat as a byproduct and expect their customers will have to replace their packs every 2 to 3 years. Careful analysis and testing of our cells, combined with our battery and thermal management systems, allows Evoke battery packs a solid balance between retaining 90 to 95% of capacity on each and every charge, which equates to a solid 200 km in city riding, while being able to have a total battery pack lifespan of 2x as long as standard lithium based cells.

That balance between power and safety transcends over to things like the UI and UX of the instrument cluster, and power output curves, state of charge estimations, and charging time estimations. Imagine something as simple as a battery gauge, yet that simple battery gauge has undergone months of tweaks, design changes and calculation algorithm adjustments. Contrary to basic coulomb counting, which is the default way to get an estimated remaining range or SOC (state of charge) estimation, vehicles have the added challenge of dealing with weather factors (such as how much more power does it take to power the vehicle across headwinds vs tailwinds), temperature factors (which can swing the SOC reading plus minus 30%), elevation, driving styles and dynamic weight of the vehicles (having a single rider, then picking up a pillion rider on the way home), all these factors play a huge role when it comes to how the calculation algorithms estimate how much is left in the battery. Best case the ECU and BMS will estimate correctly and everyone will be happy, worst case scenario, the temperature drops from your morning ride with massive headwinds on the way back home, and the bike’s ECU may estimate a 19% reduction of range. If we have an actual 21% reduction of range due to the adverse temperature and weather, that is the difference between making it home and not making it home. As an OEM, our best suggestion is to err on the side of conservative and program the ECU to update the instrumentation cluster with a 25% reduction of range, and have the rider adjust their route to ensure they make it home. That allows a buffer zone, similar to a reserve tank always ready to go aboard our electric motorcycles.

Finally, when it comes to charging speeds, ideal conditions allow the battery pack and charger combination to maximize charge rates and input the most amount of electrons within the time period, but similar to range estimations, (which is essentially discharging the pack) charging has the same environmental factors to consider. So with ideal conditions, our Evoke Generation 2 battery packs will charge within 15 mins, but if the batteries are warm from a hard run, or while our ECU and BMS calculates data from the temp sensors, onboard battery SOC, input voltage, etc, what should the charging estimate show? This plays in to that user experience again, and if we show 15 mins, then we find out the batteries are too cold to charge at that rate, do we then increase to 18 or 19 mins? Do we first show a blank time as the ECU continues to compute. At the end of the day, we all hate the Windows file transfer window that says “3 minutes to completion”, then suddenly it jumps to 9 minutes before you're done reading the text.

Ultimately, as an OEM, we need to carefully balance user’s expectations, rider’s experience and physical hardware stability, and the simplest way at the moment is to estimate things conservatively, therefore indicating to the user / rider less, and secretly giving more. Moving forward into the future, more accurate and complex algorithm estimates will be implemented, and that disparity gap will decrease.

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