Regenerative charging on descent

[Ficus]

Just had this idea. I am not an emtb owner yet but looking in to it. Mainly for self shuttling. And was just wondering. Why doesnt emtb’s have regenerative charging on the descent like cars?

 

[Stoffel]

I guess because it would be like riding with the brakes on?

 

[jerry]

Because, as with cars, it sounds a lot better than it actually works.

 

[Sherman]

It would suck the fun out of descents. And probably would not produce much energy anyway.

 

[Ficus]

Does is brake? When i release the gas on my car it starts charging but i dont feel resistance?

 

[RustyIron]

Does is brake?

Regeneration will definitely add a load on the motor, which will reduce momentum. I'm quite experienced in big motors and regeneration, but not so much with automobiles. My thoughts are that you don't "feel" it in your car is because there is little regeneration while coasting, but it is increased as you brake. It makes perfect sense, and that's how I'd program it. Another aspect of motor control is "dynamic braking." That's when you add resistance (or a regeneration load) on a rotating motor with the intention of slowing it down. You'd be AMAZED at how an excessive dynamic braking load can bring a ton of rotating mass to a screeching halt. "Screeching" is not me being hyperbolic. So the answer to your question is, "Yes!"

 

[Voluptua]

What you're trying to do is use regen instead of brakes, so the energy that would otherwise be dissipated as heat goes back into the battery. Good in situations where you're alternately accelerating and braking, like city driving, or motor racing. Or, as here, cycling in hilly terrain.

With a mid-mount motor, you'd have to lock out the freewheel at the back, and somehow sort out the derailleur jockey wheel so the chain could drive the motor (acting as a dynamo). Then, perhaps, a clutch, so the system could freewheel properly when coasting, but engage when you wanted the regen to kick in.

Perhaps a dynamo in the front wheel would be a better option.

 

[KennyB]

Google Image Result for https://upload.wikimedia.org/wikipedia/commons/c/c0/Fahrrad-detail-23.jpg

 

[Darren]

This has been discussed several times - the conclusion is always:

- too complex for the returned energy, in an environment where simplicity is valued.
- too expensive for the returned energy, in an environment where cost is already high.
- too heavy for the returned energy, where weight is critical.
- too much retardation for the returned energy, where gravity is important.

Regeneration works best (as mentioned above) when there are large masses involved and/or high acceleration and deceleration involved - busses, trucks and motorsport.