generator on electric bike?

[Chakan]

is it possible to put a generator on an electric bicycle in order to slow down, or even possible halt battery usage?

i imagine it would be placed on the wheel and take advantage of its spin, or it would take the place of the pedalling system somehow.

...thoughts??

 

[motomech]

Bikes already have things to slow them down, they are called brakes.
I'm not sure what you mean by: "...halt battery usage...", but if you are referring to recharging the battery, physics doesn't work that way.
There are no perpetual motion machines.
Even the Great Swinging Pendulum at the Smithsonian Museum of Natural History has sneaky electro-magnets in the floor.

 

[r3volved]

I think you're thinking of regenerative braking.
Your (non geared, correct?) hub motor flip to a regenerative mode that slows you down by converting some of your kinetic energy back into the battery.
You can't use both at the same time

 

[bmurray7]

If the electrical generator is always running, it won't increase range. Any energy generated will be offset by the additional rolling resistance. Since the generator isn't perfectly efficient, the net effect would be to decrease range.

If the generator is used selectively during braking, it might help. However, you would have to account for the added weight and generator energy loss.

 

[Drunkskunk]

is it possible to put a generator on an electric bicycle in order to slow down, or even possible halt battery usage?

i imagine it would be placed on the wheel and take advantage of its spin, or it would take the place of the pedalling system somehow.

...thoughts??

What you describe is called perpetual motion. The motor drives the bike, the wheel turning drives the generator, the generator drives the motor.

It doesn't work. The concept violates the second law of thermodynamics.
Or to make it simple: it takes work to make power. If you had a perfect 100% efficient generator, it would take 500 watts of power turning the generator to make 500 watts of power come out of the generator. If you then hooked up a 100% efficient motor to the generator, it would be able to turn the generator with 500 watts of force, to make the 500 watts of power to run it's self. But there would be no energy left over to make the bike move.
And there is no such thing as a 100% efficient anything.

If you have a motor producing 500 watts and it's moving a bike, all 500 watts is being used to move the bike, and not a watt is left over. if you attach a generator, the bike has to slow down because it's stealing some of the power from the motor.

 

[dogman dan]

Put it another way, If you pedal along, generating and charging the battery one mile, the effort will be like pedaling 5 miles. And then the energy you created will take you about 100 yards. Or,,, you could pedal much easier the mile and 100 yards.

It's just that horribly inefficient. Even so, you will see it used at "green parties" running the music. It's cool looking, but not efficient or even green IMO. But useful perhaps in an emergency situation. I have a crank up flashlight in my car.

Regen braking does have it's uses, it will slow you down real good, and may be very welcome if you ride huge mountains that can wear out brakes.

Regen also loosens your motor axle nuts, so it's not ideal to use it all the time, unless your torque arms are a very tight fit.

 

[r3volved]

Regen also loosens your motor axle nuts, so it's not ideal to use it all the time, unless your torque arms are a very tight fit.

I did not know that...very useful information when installing a hub motor.

 

[dogman dan]

This happens if there is any slack in the torque arm. Then the axle tries to turn one way driving, then tries to rotate back braking. This will loosen nuts fast if the slop is large.

But if you have a tight torque plate, it can't happen. A pinch type torque plate would work best. I put regen on my cargo bike, for descending huge rocky mountain passes. But I can't use it till I put some better torque arms on.