Front hub motor as regen brake?

[LI-ghtcycle]

I was just thinking, if I had an extra light front DD hub motor with minimal drag, and I had a disc brake on it, I could use regen on it as sort of a way to have my regen on a mid-drive NuVinci hub bike since it internally freewheels and disallows regen braking on the motor.

I suppose it would have to have it's own little controller, maybe I could have it generating power for a separate battery for lights or something.

Silly idea I know, but would it be do-able? :lol:

 

[amberwolf]

You could do that; personally I'd have the regen going to the main pack, with the controller setup to regen a high enough voltage to get quite a current flow, as long as your pack will take it. More current = stronger braking.

Just remember that it isn't going to brake down to zero, probably not much down past 5-10MPH, depending on the motor type and winding.

AFAIK, a higher kV motor should also regen brake by outputting higher voltages, but I might have that backwards. Basically you'd want to use whatever kind of motor outputs the highest voltage at the lowest speed, for more effective braking with it.


But: it's significant weight just to get braking forces that you can also get with good rim or disc brakes (or drum), *and* braking taht doesn't work as well when the pack is full compared to empty.


The latter can be fixed by using a pack that can handle high charging rates, and discharge it as far as possible before heading out. But it also has to be a pack that can *be* discharged to zero and left that way for a while, and charged very fast from zero, and has a high enough capacity to absorb all the braking power you will generate on a ride. (the last can be dealt with by discharging the pack with lighting or heating coils or whatever, if needed).

 

[miuan]

Just use the motor as a means of regen and supplementary propulsion. You can also use the same battery I believe, why mess with two.

 

[dogman dan]

I know how big an advantage regen can be. Especially if you stop from higher speeds. But I just don't see the big need for it though, if your bike is actually a "bike". A featherweight motorcycle is a different story. Stopping from 20-25 mph is easy, but from 30 mph on up inexpensive bike brakes sure do show thier limits.

Also a consideration, you have the motor and would have to pay for a bitchin set of hydraulic disks to improve braking. The question is, do you need regen enough to drag that motor around all the way just to use it to stop? Pedaling an unpowered motor may seem like low resistance, but that drag will increase as you increase speed. So once moving, you'd have to power that motor at least enough to eliminate that drag. Sounds hard to coordinate to me.

 

[LI-ghtcycle]

Yeah, I won't be replacing my front drum brake anytime soon, something possibly for a future project, the thought is to use the lightest DD around, (a cute 80?) and I was curious if it would be a problem using it with the same controller that is powering the motor, (this from wheel is the generator/brake) but here's another thought, I know that shorting the phase wires slows things down, what if I had a momentary switch that would do that but regulate it some-how like with a resister so it wouldn't be a dead short?

I'm just trying to think of a way I could get the advantage of regen braking and save on brake pads/shoes. I wouldn't really care if I harnessed the power generated, just the braking force, and the hub would also have a disc brake attached to the outside.

 

[LI-ghtcycle]

Just use the motor as a means of regen and supplementary propulsion. You can also use the same battery I believe, why mess with two.

That is true with a DD hub motor, I am using a mid-drive that freewheels, and I couldn't use the main motor for regen, or that would be very easy to do, especially with the controller I have from Lyen.

 

[amberwolf]

I was curious if it would be a problem using it with the same controller that is powering the motor,

Can't do that unless you rig up relays to disconnect your drive motor and connect your braking motor, for halls and phases, every time you wanna use it to brake. Probably gonna blow the controller switching at some point if a relay sticks.

I'm just trying to think of a way I could get the advantage of regen braking and save on brake pads/shoes. I wouldn't really care if I harnessed the power generated, just the braking force,

Then you don't need a controller, just a way to short the phases together--plug braking. Best way is to use coils of wire around your bike frame, one for each phase pair, and relays turned on by brake lever switch to short phases together. Short one set for litle braking, two sets fro more, etc.