Replace rear brake with variable regen

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Replace rear brake with variable regen

Post by flat tire » Dec 20, 2017 7:11 pm

Looking at getting a Kelly to run a Leaf 1500 build at around 200 phase amps / 80 battery amps and do variable regen. If anyone has a less expensive recommendation that would be nice but mostly I'm interested in your experience with how well this works and what sort of control you use for it. I would like to use a traditional brake lever with a pot. Anyone have a good idea for a strongly progressive loading on the lever so I have some feedback there about how much brake I'm asking for?
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Re: Replace rear brake with variable regen

Post by amberwolf » Dec 21, 2017 2:02 am

I don't have progressive / variable regen, but I can say that the on/off EABS (stronger than just regen, as it actively brakes the motor, and goes down to nearly zero RPM where regen doesn't always go below a few MPH), on my SB Cruiser's left wheel (regular regen on the right, presently) brakes really hard--if it were on a regular bicycle, it'd probably skid the wheel (the trike is too heavy back there for that to happen; if it were on the front wheel it might skid it).

If it were variable, it'd be a great brake. Since it's not, there are situations where I have to use the regular front brake to slow a bit first and then use the EABS + regen (left and right are linked),

So I'd guess you'll like variable regen (or better, EABS if you can get it), as long as you can set it strong enough.

Mine is just a generic ebike controller, nothing special, so I'm sure there is better stuff out there with good braking setup. If you're willing to build a controller and power stage, you could look into the Lebowski stuff. (I've been collecting the parts to build a pair for a while, partly just to get variable strong braking).



A few ways to simulate a load on the lever, that I've considered:
--You could use a cable from the lever to a spring load.
--Or to a brake pad on a pivot pressing against the frame instead of a rim. (the spring load would probably be easier to make small).
--Or directly use a spring (leaf instead of coil) to the lever so it has to bend it as you pull.
--Or a pull-coil-spring from the lever out the cable opening to a mount on the bars or stem (or something else mounted on the lever housing, if you can find a spring narrow enough for that that still has the tension you need.
--simplest I can think of is an elastomer block under the lever (on the bars/grip) that squishes as you brake, but I'm not sure what would be compressible to the right extent.

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Re: Replace rear brake with variable regen

Post by dogman dan » Dec 21, 2017 8:28 am

I had non variable regen at one point. The cool way to do that one was with a push button, and still have regular rear brake too.

I liked the way I could choose regen, or not. That way it did not need to be variable. Simple, but effective.

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Re: Replace rear brake with variable regen

Post by 2WheelsMovesTheSoul » Dec 21, 2017 1:02 pm

I've got another 2 weeks before the remaining parts for my winter project arrives, but I'll be using a Kelly KLS-7230S to take advantage of it's analog regen feature. I too, thought about ditching the rear brake entirely. I really feel a bit safer with something I can lock up in an instant rather than waiting even a half second for the controller and motor to start regen braking. After all, my target top speed will be in excess of 50mph.

My previous ebike had a on/off regen activated by untwisting the throttle, you still had to have some throttle just less than before. This type was more like a linear ABS than an actual brake. It would active but it took several days to learn how to modulate the throttle in such a way that it felt like a brake. Even then it was tricky because when you dropped to less than 7-8 mph the regen would just stop working and you'd have to grab a handful of brake anyways.

I'll be using a Bafang 0-5v universal thumb throttle for the variable regen, as well as a OEM style motorcycle brake master (16mm piston) squeezing a OE/MC rotor. I'll have a 5v relay that activates at 3.6v hooked to a 12v brake light. The OEM lever also has a regular 2 wire switch to kill power to the motor/ activate brake lights if I choose to use the actual rear brake.

The thumb throttle is spring loaded and has some resistance but probably not the kind of 'feedback' you're looking for. I guess you could open it up and add a 2nd spring that adds a bit more tension at the halfway or 3/4 mark, maybe add a chunk of rubber at the half or 3/4 mark.

I'll post back once I've got it running and let you know how Kelly's version of regen braking works. Personally, I'm curious to know if slows the motor down to 0 rpm or if it lets go at some other programmed/specified rpm.

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Re: Replace rear brake with variable regen

Post by flat tire » Dec 21, 2017 11:42 pm

I want to be able to lock her up with the regen, but also delicately modulate to adjust the bike on the trails.
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Re: Replace rear brake with variable regen

Post by Alan B » Dec 22, 2017 12:13 am

My CroBorg doesn't have much room for a rear disc with a Cromotor in a 135 dropout, so I jumped at the chance to set up variable regen with the Sabvoton. I took an ebrake lever apart and replaced the cable puller with a magnet and linear hall sensor. The Sabvoton needs a switch closure and an analog voltage for electric braking which is a superset of regen. It feels different from a brake because the lever position maps to braking force, rather than lever force mapping to braking force. But it is easily managed and works great.

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Re: Replace rear brake with variable regen

Post by Buk___ » Dec 22, 2017 12:34 am

flat tire wrote:
Dec 20, 2017 7:11 pm
Looking at getting a Kelly to run a Leaf 1500 build at around 200 phase amps / 80 battery amps and do variable regen. If anyone has a less expensive recommendation that would be nice but mostly I'm interested in your experience with how well this works and what sort of control you use for it. I would like to use a traditional brake lever with a pot. Anyone have a good idea for a strongly progressive loading on the lever so I have some feedback there about how much brake I'm asking for?
I think that a strain gauge applied to a suitable component of the break lever or caliper would be the perfect way to translate pull force into a signal suitable for controlling regen braking.

They don't come cheap though, and you'd need some circuitry (whetstone bridge and maybe an opamp) and some trial and error to configure it.

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Re: Replace rear brake with variable regen

Post by dogman dan » Dec 22, 2017 8:45 am

No room for a disk, or no way to even keep a rim brake, would be the big reason to want variable regen.

lots of others will read too, so I just wanted to point out how good it can be to keep the mechanical brake if possible, and just jab a button to get additional non variable regen brake.

It is very easy to modulate a handle, and still jab the regen button with your thumb.

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Re: Replace rear brake with variable regen

Post by flat tire » Dec 22, 2017 11:52 am

Buk___ wrote:
Dec 22, 2017 12:34 am
strain gauge
OK, that is a great idea, thank you! My brake can be like a F16 joystick which would be great.
Orange DH w/ Cyclone mid on 6kw
Gary Fisher w/ Leaf hub on 6kw
RC Lipo and domino throttles only!

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Re: Replace rear brake with variable regen

Post by Buk___ » Dec 22, 2017 2:50 pm

flat tire wrote:
Dec 22, 2017 11:52 am
Buk___ wrote:
Dec 22, 2017 12:34 am
strain gauge
OK, that is a great idea, thank you! My brake can be like a F16 joystick which would be great.
Another thought would be to apply the strain gauge to the stop inside a twist or half-twist throttle.

To apply the brakes you roll the throttle off and the apply a reverse torque against the stop.

As you're braking-by-wire, you can set the required torque to be as firm or gentle as you like.

With a little practice, you could even use your thumb to apply the regen rear brake, whilst your fingers apply the front, and even modulate between them.

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