Variable regen drag brake for tandem bike w CA3 & PhaseRunner

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Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by jlaplante » May 10 2019 11:16pm

Hi all -
I just electrified a nice Santana tandem road bike using all the latest Grin tech stuff:
- Crystalyte H3525 DD front motor
- 52V 16AH battery
- PhaseRunner controller
- Cycle Analyst v3
- PAS plus manual throttle override

Since tandem bikes descend like greased lightening, many are equipped with a third “drag” brake, typically a rear drum brake that can be set-and-forget for the duration of a long descent.

Variable regen braking would be perfect for this application. I envision a small potentiometer (or perhaps a switched pot) that can be rotated up from its zero position to engage regen that is proportional to the pot’s position. Variability of regen is important to tune speed. After descent it will be manually rotated back to zero.

I can’t figure out how to do this with the CA3 + PhaseRunner, or at least without losing my manual throttle.

Any ideas anyone?

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by amberwolf » May 10 2019 11:58pm

First, keep in mind that the motor will heat up, possibly quite significantly, during this type of usage. The controller may as well, as may the phase wires.

Also, HVC on either battery BMS or controller may cause braking to unexpectedly cease, so be careful with that.

If the battery isn't far enough discharged when you start this usage, then that could happen pretty quickly.


Now, for a possible way to do it:

Since AFAIK the PR uses the range between 0 and 0.8v for regen control, you *could* make a switch that changes from "motor mode" to "drag brake mode". It would switch the PR's throttle input from the CA's output to the control device (pot, etc) that you wish to control braking level with. If you use a pot, you just have to put it at the bottom of a voltage divider that leaves teh pot's voltage range output the same as the PR's regen range input.

To make this all one unit, you could use a pot that is attached to a switch. There are various types of these, that turn on/off the switch at the far counterclockwise position. The pot works like any other pot.

The switch is usually just an SPST, on-off, so it wont' do the job needed, but it *can* be used to switch a relay on and off, that *can* be used to switch the pot/throttle.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by john61ct » May 11 2019 8:11am

I'm very interested in this for a long cargo, so far planning on using a NOS Arai on the rear.

Is the actual regen functionality that effective, to get good usable range extension from a long descent? I'm thinking might be worth having on the front regardless, just to be able to alternate the heat load?

Is overtemp monitoring / protection on the motor / controller / wiring already built in, or practical to implement?
amberwolf wrote:HVC on either battery BMS or controller may cause braking to unexpectedly cease, so be careful with that.

If the battery isn't far enough discharged when you start this usage, then that could happen pretty quickly
What about the HVC diverting load dump to resistance?

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by amberwolf » May 11 2019 2:58pm

john61ct wrote:
May 11 2019 8:11am
Is the actual regen functionality that effective, to get good usable range extension from a long descent? I'm thinking might be worth having on the front regardless, just to be able to alternate the heat load?
On a long enough bike, with the primary load far enough back, the rear can have enough traction to make stronger braking back there a possibility. On a regular length bike, so much weight transfers to the front wheel that less traction will be available back there, so the rear brake may just skid if it's hard enough braking (probably worse on a steep downhill slope, too). But the front should have good braking either way.

(some bikes may be an exception, like my SB Cruiser trike, that has MUCH better traction in the rear because so much of it's weight (and mine) is on it, so if I had the same brakes in the back that I do in the front, I'm not sure I could skid those wheels where the front does fairly easily; this is the opposite of normal. Weight transfer still occurs druign braiking, just not enough to change the problem sufficiently).


Range extension....that depends on your battery condition at the time of braking usage. If it's not discharged, you don't get any extra charge. If it's partly discharged you can get the amount of charge total taht's the difference beween present SoC and full.

So, let's say your big down hill is early on in your trip--much of the power may be unrecoverable just because you have nowhere to put it. :/

Typically you only get back a few percent of the total power used. Sometimes people ahve gotten as much as 10-20% recovery under conditions long/steep downhills, but you also have to use a lot more power going *up* the hill either to get to the top of the downhill, or to go back up the other side (or both), than you would just riding on the flats anyway. If you already know you have to go uphill / downhill, having the ability to recov er somefo that power is good...not *havng* to do it in the first place is better (alternate routes, etc).
Is overtemp monitoring / protection on the motor / controller / wiring already built in, or practical to implement?
Depends on your motor and controller. Some do, some don't.

Practical depends on your willingness for DIY. ;)

There's many ways to do thermal control, including completely manual, using BBQ thermometers (remote or wired). Plenty of threads/posts about various sensors, controls, etc.


What about the HVC diverting load dump to resistance?
Sure...but the resistance is likely to be a different load than whatever regen level was allowed or set just prior to HVC, and may be quite a sudden severe change. You can make a switchable bank of wire coils around your frame (rather than plain resistors; it's a lot of heat), so you can switch in more for more braking or less for less braking, etc.

Here's a catch, though:

When you switch the battery output of the controller from the battery to the resistors, it's basiclaly going to short out the battery, so you have to *first* disocnnect the battery from the system, and *then* connect the resistive load. It doesn't have to be a long time between disconnects, even just a break-before-make contactor, but it does have to break first. And the same when disocnnecting the load and connecting the battery. If contacts ever stick in the contactor, you could short the battery out (hopefully it's BMS would simply shutdown, or whatever fuse you have in the system would blow, and protect the battery).

Another catch: During the instant of disconnect, either way, if there isn't enough energy at a high enough voltage to run the controller, it'll shutdown and stop doing any regen/etc. Some controllers may not "restart" while moving, either, (give some error condition and require a power cycle while stopped to fix) or they restart in some unusual condition that isn't what you want/need at that moment (most will rpobably be fine though).

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by john61ct » May 12 2019 2:21am

Great stuff thanks.

So to resolve that last issue, I'm thinking a little "UPS" string for just powering the controller, maybe also gauges, USB nav lights, also for after the LVC isolates the main bank, "limp home" mode under pedal power.

____
Since I'll already have the Arai drag brake in the rear - and yes with lots of weight back there,

I'm thinking a second drag brake "for free, "built into the front hub motor, would just help spread the load, act as an alternate heat sink. The regen as power source would just be gravy.

I think would still do hydraulics for true (sudden / emergency) stopping security, not depend on those for long-descent dragging, treat as pretty much separate systems.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by jlaplante » May 12 2019 10:11am

amberwolf wrote:
May 10 2019 11:58pm
Now, for a possible way to do it:

... you *could* make a switch that changes from "motor mode" to "drag brake mode"...

...you could use a pot that is attached to a switch...
Thanks amberwolf - that sounds pretty simple. Will the PR controller make this mode change smoothly? Any kind of hiccups I might expect?

Being so straightforward, I’m tempted to ask the next logical question - would it be possible to also add variable regen via my rear brake lever to this setup?

That would be the killer app - regen braking for normal stop & go riding, plus my drag brake for long descents.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by john61ct » May 12 2019 12:29pm

You mean two motors to coordinate for propulsion too?

Or regen-only, a motor specifically dedicated to drag braking?

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by amberwolf » May 12 2019 3:56pm

jlaplante wrote:
May 12 2019 10:11am
Thanks amberwolf - that sounds pretty simple. Will the PR controller make this mode change smoothly? Any kind of hiccups I might expect?
Don't know; never used a PR, but you can try it and if any hiccups occur, we may be able to work out a solution for them.
Being so straightforward, I’m tempted to ask the next logical question - would it be possible to also add variable regen via my rear brake lever to this setup?
As long as you can add a variable voltage output sensor to the brake lever or cable, that outputs the correct voltage range. You can either have it directly on the lever, or use a cable splitter (or dual-cable-lever) so one goes to yoru mechanical brake, and the other to a potbox. To get the right output range you can either use op-amps or transistors, or arduino or other MCU.

AFAICR the CA does support variable regen braking for controllers liek the PR, but the level is controlled by your throttle, not the lever--the lever just activates it.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by jlaplante » May 12 2019 4:20pm

Thanks - any suggestions for a source of a “variable voltage output sensor”? Are there any good threads on this board about such a setup?

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by amberwolf » May 12 2019 4:40pm

I know there are a number of discussion, but I can't find them in a search easily.

These come up ina titles search
https://endless-sphere.com/forums/searc ... mit=Search

these come up ina first post search
https://endless-sphere.com/forums/searc ... mit=Search

some poeple have put straing agues on levers or calbes, some use analog hall sensors liek in a throttle, some used the brak ecable to pull a throttle munted in a box/etc instead of a mech brake, and so on. ebikes.ca had some premade levers for this purpose at one time, dunno fi theys till ahve them.

but the easiest is a split or dual cable runing one to themech bakre and the other to a potbox. if it's actuallya pot you could use a voltae inptu to the pot that's only 0.8v so t anaturealy scales 0-0.8v off to full on. then arrange the cable pull so it pulls the potbox zero to full on bfore engaging the brake pads.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by amberwolf » May 13 2019 12:00am

Looking something up for someone else, I found this, that may be helpful, in the CA menus:
[ SLim->Regen Lmtg ]
Chooser to select if Speed Limiting should use regenerative braking to help control the maximum speed.

Disabled: Speed is limited exclusively by reducing power. Above the speed limit the motor power is reduced to zero, but regenerative braking is not applied allowing the rider to continue to coast or pedal above this speed limit. [Default]

Enabled: Regenerative braking is used to enforce the speed limit setpoint. This means that regen may engage automatically when descending hills even without the rider applying the ebrakes. Proportional throttle regen (EBk->PropRegen) need not be enabled. This feature requires a controller with 0.0 - 0.8V throttle regen function (e.g. Grinfineon or Phaserunner).

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by 999zip999 » May 13 2019 10:36pm

They have BT controllers that you can change regen with your phone. But would need to hit the flash button to reset. With phone on handle bars. A little clumsy.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by amberwolf » May 13 2019 11:27pm

The last time I saw someone post about that, there was a mention that the system had to be power cycled for the new settings to take effect. Kind of impractical while riding.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by 999zip999 » May 14 2019 12:10am

Yes be still can easily adjusted , but not really on the fly. It's like on the other side of the mirror.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by robbie » May 30 2019 12:07pm

jlaplante wrote:
May 10 2019 11:16pm

I can’t figure out how to do this with the CA3 + PhaseRunner, or at least without losing my manual throttle.

Any ideas anyone?
The CA3 has variable regen enabled on it by default, you just need to tell it to enable the feature with the ebrake connection

The easiest solution is to hook up an eBrake switch of some kind into the eBrake plug on the CA3. Once this switch is enabled, the CA will put out a lower voltage (default is 0.5V) and increasing the throttle signal will decrease the CA's voltage output to have the Phaserunner controller increase the braking torque.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by justin_le » May 31 2019 2:56am

jlaplante wrote:
May 10 2019 11:16pm
Variable regen braking would be perfect for this application. I envision a small potentiometer (or perhaps a switched pot) that can be rotated up from its zero position to engage regen that is proportional to the pot’s position. Variability of regen is important to tune speed. After descent it will be manually rotated back to zero.

I can’t figure out how to do this with the CA3 + PhaseRunner, or at least without losing my manual throttle.
The answer to doing this as you lay out here is explained in section 5.3 of the user manual:
PR Separate Ebrake Input.jpg
https://www.ebikes.ca/documents/Phaseru ... Rev2.0.pdf

Separate out the blue wire from the throttle plug and wire it up to a potentiometer, then change the ebrake mapping range to match that of a pot (say 0.5V to 4.5V). Whenever the pot is turned up above the threshold voltage then it will switch the phaserunner into regen mode and you can dial the regen intensity up and down. This will be constant torque regen, so the braking force on the wheel will be constant (and set by the pot) regardless of your speed.

The other approach was suggested by Amberswolf, and that's to use the CA3's speed limiting feature with speed limit regen enabled. This will will automatically vary the regen intensity to maintain constant downhill velocity, and in that case I'd recommend wiring up the pot to the CA3's aux input and using that to set the vehicles speed limit.

So in option a) you use the pot to tweak the braking torque and the velomobile speed will still fluctuate up and down with the grade while the braking force stays constant. In option b) you use the pot to set your speed limit on the downhill and the CA3 will automatically regulate the regen braking force in order to keep that speed constant even as the downhill grade changes, so you'll have more regen on steeper sections and less on flatter sections.
Any ideas anyone?
I have many more ideas too, but those two are the most sensible ;-)
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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by BlueSeas » Sep 04 2019 5:36pm

My first post to this forum after lots of reading. Thanks to all the contributors.

I'm planning the wiring for my first Ebike build using a CA3, Phaserunner and 9C 212 hubmotor. There is a somewhat recent video, I've lost the link, showing Justin (I think) stopping an ebike going down a reasonably steep hill using regen all by itself. Sold me on the concept.

I think I understand how to use the pre-designed implementation for CA3/PR, believe it requires activating an ebrake, then using the throttle. But I'd rather have a separate control for variable regen. Planning to use a repurposed thumb throttle. This thread answered one key question...what happens if the Phaserunner has both an active throttle signal and an ebrake regen signal. The ebrake wins. All good so far.

But...what happens if the CA3 cruise control feature is active? Use only the regen control to come to a stop, what happens when you release the regen control? Since there was no ebrake signal sent to the CA3, I'm assuming it might attempt to return to cruise speed. Those cautions are in the detailed CA3 manual posted here. That's no good if so.

For the forum:

1) Ideally, the CA3 should sense the regen (what else would cause the current sense electrons to run backwards) and programmatically release the cruise control setting. Maybe it does? Anyone tried this?

2) If not, the second thought is to place a NC reed switch such that if the regen control is moved, it becomes the third ebrake input to the CA3. Still working on the mounting of such a solution, but it shouldn't be too hard. Is there a better workaround?
Last edited by BlueSeas on Sep 06 2019 6:13am, edited 1 time in total.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by amberwolf » Sep 04 2019 7:00pm

BlueSeas wrote:
Sep 04 2019 5:36pm
But...what happens if the CA3 cruise control feature is active? Use only the regen control to come to a stop, what happens when you release the regen control? Since there was no ebrake signal sent to the CA3, I'm assuming it might attempt to return to cruise speed.
Since the CA doesn't know you braked, it's still outputting the same throttle signal until you tell it otherwise. So once you release the brake, the PR should see the throttle input is active and do whatever it's set to do for that.




1) Ideally, the CA3 should sense the regen (what else would cause the current sense electrons to run backwards) and programmatically release the cruise control setting. Maybe it does? Anyone tried this?

AFAIK it doesn't do that. You could try to convince Grin to change the firmware to do that, though it may cost you other features to make space in the memory for this one. If you really need the feature, they do custom firmware but it is expensive.
(what else would cause the current sense electrons to run backwards)
Charging will also do this, if like me you have the charging input on teh controller side of the shunt.
2) If not, the second thought is to place a NO reed switch such that if the regen control is moved, it becomes the third ebrake input to the CA3. Still working on the mounting of such a solution, but it shouldn't be too hard.
That's the only option I know of.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by BlueSeas » Sep 04 2019 8:08pm

amberwolf, Thanks for the reply!

I had to smile at the thought of having cruise control active while charging!

Will put in an enhancement request for Grin. There is a spot on the product information page. Surprised that they are out of room already since the V3 CA isn't that old.

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Re: Variable regen drag brake for tandem bike w CA3 & PhaseRunner

Post by NCC1941 » Sep 04 2019 9:06pm

If you're activating regen through the CA3, it WILL release the cruise control. I do it all the time.

If you connect your regen throttle directly to the Phaserunner, as you suspected, the CA3 will have no way of knowing that the ebrake has been applied, and it probably won't release cruise control.

The way I got around this was to parallel connect two throttles to my CA3 - a thumb throttle for normal throttle use, and a dedicated mechanical brake lever connected to a cable -> hall signal throttle converter. The brake lever has an ebrake sensor, and the cable tension is calibrated so that the 'throttle' signal on the brake lever kicks in just after the ebrake signal activates. That way, I have a normal throttle *and* a brake lever that controls variable regen, both wired up to the CA3 with no control conflicts.
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CA3 CAv3 Cycle Analyst feature wishlist request

Post by amberwolf » Sep 04 2019 10:25pm

BlueSeas wrote:
Sep 04 2019 8:08pm
I had to smile at the thought of having cruise control active while charging!
Not a likely circumstance...but possible, if for instance you have solar panels on the bike/trike/etc., and their output happens to be more than the motor is taking.
Surprised that they are out of room already since the V3 CA isn't that old.
It's actually several years old, and they're already at v3.1.12 or .13 or something, so many minor revisions.

Last I recall, in either the Solar CA thread or the CA 3 beta thread, Justin said something about having had to take some other feature out to add the most recent new one. Sometime in the last several months, IIRC, but don't remember what it was about.

He's also said that there's a new hardware version in the works, to help with that, and some other stuff, but I don't recall him saying anything about exactly what that would be.


There are a number of things I would personally like to see fixed and added to the CA'; off the top of my head a here's a short list that doesn't involve hardware changes:

--separate PAS and throttle throttle settings, so neither affects the other and are completely independent.

--more than three presets (say, at least 10).

--PAS scaling values that allow using large amounts of power from a stop when applying full (or at least high, referenced to whatever the presetn settings are) torque to the cranks, for heavy cargo bikes/trikes and the like.

--PAS scaling curve creation on the PC setup utility to allow a user to tailor power application to their needs vs the bike/trike's ability to keep placing torque on the cranks, etc., and to allow fading out of torque control into cadence control. This is especially useful for trikes like mine that are geared VERY low for the cranks, so that I could pedal it home without power if necessary, at a couple MPH or less, but that don't have a gear high enough to allow torque to be placed on the cranks at all above a few MPH, yet the rider wants to continue to apply motor power above that speed using PAS only.

--PAS ability to start with torque-only, with a settable "start limit" so you can't accidentally engage power but have to apply some higher level of torque to the cranks (but doesn't require rotation of cranks to engage). (This would not only allow the use of PAS-only control of a heavy cargo bike/trike, but also using torque-based (or other control method) sensors of non-rotational input devices, without having to use the throttle input for them instead with some external conversion electronics).



And a few that do involve hardware:

--twin throttle outputs on independent wires, each with their own settings just like the single throttle does now (for dual motor setups).

--twin throttle inputs on independent wires, , each with their own settings just like the single throttle does now (for dual motor setups).

--modes to use the above such that they can be "merged throttles" (either throttle controls both outputs, higher throttle percentage "wins" if both are in use) or "independent throttles" (each controls it's own output).

--analog ebrake input and (optional) output, each on it's own wire

--PAS ability to reverse the motion of a trike/etc, by rotating cranks backwards. This would have the CA engage a new output (with 1/0 settable output mode) to engage the reverse mode of whatever controller was in use, and then output the throttle requested by the cranks. Since the cranks in reverse on a bike/trike generally just spin this would use cadence-sensor-mode only, as there wouldn't be torque control over it when using a typical (non-coaster-brake) bicycle-type drivetrain.

--isolated power input to the CA, from it's internal electronics and output wiring. This *might* help prevent CA destruction from phase/hall shorts and the like, if the grounds weren't the same.

--overvoltage protection on all inputs and outputs, to prevent damage to the CA during various wiring and component faults (especially stuff like the two common ones: axle wires mangled in crash/etc, shorting battery voltage stuff and low votlage stuff together, and throttle signals and/or 5v power being shorted to battery voltage when rain/etc gets into a throttle that has a battery-level meter built in.

--overcurrent protection on the outputs, especially on the 5v and 10v power lines, so you can't destroy your CA just by hooking up a PAS sensor when your battery is more than whatever the limit is (60v? I forget). Or a better LVPS that cant' be destroyed like that. Or both. ;)


I expect that Grin will say there's simply not enough demand or value for any of these features to be implemented, so I haven't submitted them. (but thought I'd type them in here as a reference anyway).

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