I wrote earlier an inquiry re: the progress of backward-pedaling mediated variable regeneration:
Justin discussed offering a technique of applying variable regenerative braking by sensing backwards crank spinning, where faster spinning commanded more regen, and slower spinning commanded less. I see this listed without an ID in the "planned features" list on Grin's CA3 page.
With the current system of throttle-mediated regen intensity I need two hands or good finger dexterity on one hand to effect variable regen, one hand (or finger) holding down a button or partially engaging a brake lever while using the thumb or opposite thumb to vary the throttle. It's a slightly awkward arrangement that I can manage ok, but my fingers get fatigued on long descents when I use regen. In this case, "long" is 15 minutes or longer.
I'm not sure how workable backward-pedaling regen is on some drivetrains as fast backward pedaling can throw a chain if the return chain run is long or the chain becomes stiff. But, I'd like to try it some day.
Can you give us some idea when this feature might be available?
After riding again yesterday and descending two 500+ meter descents, using regeneration to recover significant energy, I thought of another way to relieve some hand/finger fatigue during long regeneration sessions like this, that may work more smoothly and not suffer the downsides of backward pedaling (thrown chains, pedal clearance issues in corners, etc.).
Would it be possible to add variable regeneration control to the AuxPot function?
The way I visualize this is that when one is in regeneration mode (i.e. eBrake circuit closed), one could adjust the AuxPot to adjust the amount of regeneration. What would be particularly useful is to adjust the AuxPot to set the vehicle speed the CA3 attempts to hold, while varying the amount of applied regeneration.
I've found that using a speed cruise control or AuxPot to set driving (powered) speed to give somewhat uneven, jerky behavior over slightly varying terrain, causing the bike speed to drift about the set speed. I much prefer when driving to have AuxPot adjust current or power (when power is applied by PAS activity). But, for regeneration I think vehicle speed may be more useful parameter to adjust than power.
Downhills vary their grade over short distances, and a constant power/constant current approach to regeneration will result in speed that varies too much, to the point of stopping the vehicle if the grade levels out for a short distance. When descending one is generally moving faster than when climbing, at least on a low-powered e-bike.
I find that when I use regeneration on descents, I'm aiming to hold a moderate descending speed that is a compromise between being too fast to recover significant energy that is otherwise lost to wind resistance and so slow as to be tedious. My usual descending speed when in regeneration is usually between 25-40 kph.
So the added functionality I visualize would allow one to optionally set a MaxRegenSpeed and adjust the RegenSpeed between MaxRegenSpeed and 0* using AuxPot, when the CA3 eBrake circuit is closed. The CA3 will then vary throttle output in accordance with the eBrake protocol (0.85 down to 0.0 volts) to maintain a vehicle speed no greater than the RegenSpeed. The throttle itself would continue to function as it does currently, allowing the user to apply more or less regeneration on demand, overriding the RegenSpeed setting.
*It may be more intuitive for RegenSpeed setting to be lowered with advancing AuxPot position, the full-CCW position of a higher RegenSpeed resulting in the least amount of regenerative braking applied, and a full-CW position of a lower RegenSpeed resulting in the highest amount of regenerative braking applied. The AuxPot would adjust the speed downward with advancing position.