teslanv wrote: ↑
Apr 16, 2018 9:13 am
There is absolutely NOTHING more confusing to the inexperienced ebike purchaser that understanding potential range with respect to the ebikes they are considering. So many ebike manufacturers and retailers embellish range claims using tricks that we experienced ebikers know are deceptive at best and down right ludicrous at worst.
Factoring Human power into the calculation is something I personally feel needs to be eliminated, because you just can't make a realistic and honest assessment between two individual humans and their power output.
Range should be based on motor power only, at a specific speed, and under the most simple conditions. And the values used should be towards the conservative side of the spectrum, that one can reasonably expect to achieve, if followed.
I propose the value of 20 Watt-hours per mile at 20 MPH, since the current US ebike guidelines limit legal ebike speeds to 20 MPH, and this is a speed that can be achieved relatively easily with a legal 750W motor. Conditions would also include: a flat, smooth road, no stopping & starting or hills, on an upright mountain bike (high drag coefficient).
The intent is NOT to argue about the minor efficiency differences between system A (DD Hub Motor) vs. system B (Mid Drive) vs. system C (Geared Hub) etc. Yes, there will be minor differences in the efficiencies of these systems.
The POINT is to make a simple method for less experienced ebike customers to assess range between the different bicycles they are looking at, and the most critical component of range is the energy capacity of the battery, in Watt-hours. I argue that WATT-HOURS should be THE ONLY value that can be reasonably compared between any number of ebike power systems.
And the Formula for Calculating range should be as follows:
Battery Nominal Voltage x Battery Capacity (Amp-Hours) / 20 Watt-Hours/Mile.
48V-12Ah Battery - would have 48x12 = 576 Watt-Hours of Energy / 20 WH/Mile = 28.8 Miles of range (at 20 MPH, motor only).
Apologies to the rest of the world that uses the metric system. The equivalent of the above formula would be 32 KPH speed, and 12.3 Watt-Hours/Km, which is much less easily remembered.
Perhaps Endless-Sphere could create a "Certification" for Ebike manufacturers and retailers who agree to use our formula for range calculation in their advertising...
Call it draconian if you want, but I think the ebike buying community would greatly appreciate some straight talk with respect to range, even if it is very generalized.
Here's my Youtube Rant. (NSFW warning)