Range is the 1st question a shopper wants to get answered when shopping for an electric vehicle, it's the question they will NEVER get a satisfactory answer to, range on an EV is something you figure from riding not before. Gasoline vehicles have wide range sollution sets too but, "recharging" a gas tank takes 10 minutes or less & a battery takes far far far longer to recharge, effectively making recharging stations a destination instead of a stop off. This is why hybrids are so attractive, you get the range enhancements of being able to top off or exchange a tank in a few minutes while getting the torque & efficiency perks of an electric drive system... in the better hybrids, I can't say enough bad about the Prius & it's drive train.
Figuring range takes into account load, terrain, speed & rider effort when talking about an electric bicycle. These things have to be figured against the voltage of the motor & the amperage/Kwh power/size of the battery along with the efficiency of the system. Now in due time most of this will be able to be figured very accurately from studying performance over terrain, with loads, at speeds but, the equation will NEVER be able to accurately figure for rider input & rider demands. This is the same issue for figuring gasoline range, you can figure the mechanical possibilities but, you can't figure for what the head winds might be, how the driver will feel or if they like to drive fast & accelerate hard.
What can a rider do about it? Well I decided how far I needed to go & I wanted to be able to go more than twice that far, just incase. I needed 20 miles over terrain that was the equivalent of climbing a 30 story building so I wanted a system that could take me more than 40 miles & I got one that could effectively climb a 50 story building over that span.
If I rode the system hard using full assistance, I might get 20 miles out of it & I might not. That's the subject of my next range test, steady climbing up a steep grade for as far as I can or 6.75 miles whichever comes 1st. We may never get an accurate estimate for KpB (kilometers per battery) but, we can certainly get a fair minimum & reasonable maximum range estimate for reasonable conditions.