Alan B
100 GW
There seems to be confusion regarding the efficiency of motors at low throttle. Yes, efficiency drops a little, but not as much as you would think from looking at the efficiency graph from the Simulator (at ebikes.ca).
Why is this?
The Simulator is an excellent tool, however we must understand what it is graphing. One popular view is basically a calculation of a full-throttle run-up to maximum speed and beyond. At the single point where acceleration is zero on the graph, the system efficiency is correct. At ALL other points on the graph, the system is either accelerating or decelerating, so the power in is powering not only the motion, but also the acceleration (or the deceleration is adding power to the system). So in those cases a simple calculation of power in versus load does not yield the expected efficiency.
Let's take a simple example. If we bring up the simulator with default values and zero out the human power default, then enable System B and set it's throttle to 50%. We see that at full speed, the system efficiency is 81.5%, and at half throttle the efficiency is 75.9% for an efficiency loss of only 5.6%. This is going from 600 motor watts to 124, which is quite a wide range. There's no big penalty. The range also goes from 47 to 122km. Pretty efficient at half throttle.
Note that this is not the only way to view the simulator data, but the simulator documentation is not clear on how it should be viewed, and I think this view is closer to what most people expect when they look at the graphs. Another view will be discussed below.
Why is this?
The Simulator is an excellent tool, however we must understand what it is graphing. One popular view is basically a calculation of a full-throttle run-up to maximum speed and beyond. At the single point where acceleration is zero on the graph, the system efficiency is correct. At ALL other points on the graph, the system is either accelerating or decelerating, so the power in is powering not only the motion, but also the acceleration (or the deceleration is adding power to the system). So in those cases a simple calculation of power in versus load does not yield the expected efficiency.
Let's take a simple example. If we bring up the simulator with default values and zero out the human power default, then enable System B and set it's throttle to 50%. We see that at full speed, the system efficiency is 81.5%, and at half throttle the efficiency is 75.9% for an efficiency loss of only 5.6%. This is going from 600 motor watts to 124, which is quite a wide range. There's no big penalty. The range also goes from 47 to 122km. Pretty efficient at half throttle.
Note that this is not the only way to view the simulator data, but the simulator documentation is not clear on how it should be viewed, and I think this view is closer to what most people expect when they look at the graphs. Another view will be discussed below.