Regenerative braking help?

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Eastwood   100 W

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Regenerative braking help?

Post by Eastwood » May 01 2021 10:14pm

What’s up everybody!

I have a simple question regarding region for a Sabvoton controller.
So the Sabvoton controller Im using has regen but there’s no connections from the controller.
The controller Bluetooth app has two different settings,
Regen current (A)
Regen start speed (RPM)

Maybe with this kind of regen it only works once you reach the desired RPM?
I was hoping I could activate the region through a momentary switch to use for breaking force. Is it possible to hook a momentary pushbutton with this type of region maybe through the break cut off switches?

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Re: Regenerative braking help?

Post by amberwolf » May 01 2021 10:41pm

If you have no ebrake wires from the controller either as a pair for a switch for on/off braking or as a triple for a second throttle for variable braking force, then the only other way it could work is "slip regen", where when you roll off the throttle (rather than letting it go completely) it attempts to brake the motor to match the new speed or torque level. Letting it go completely simply cuts power but doesn't brake, for most ocntrollers in this mode.

What "sabvoton" (of which there are several manufacturers with totally different controller designs/etc) actually does, I couldn't tell you; you'd have to experiment.

But most of the time, a regen start speed would be the lowest speed at which regen will activate, *or* the highest speed at which it will activate. Which one, you'd need to test to find out.

Regen current is probably battery amps of negative current, and is a limit to prevent damaging a battery from overcharging current, as well as to allow you to limit the max braking torque you may get.

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Re: Regenerative braking help?

Post by Eastwood » May 01 2021 11:00pm

amberwolf wrote:
May 01 2021 10:41pm
If you have no ebrake wires from the controller either as a pair for a switch for on/off braking or as a triple for a second throttle for variable braking force,
The controller has ebrake wires. So would I connect a throttle to the E brake wires or maybe a momentary button to try and activate the regen?
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Eastwood   100 W

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Re: Regenerative braking help?

Post by Eastwood » May 01 2021 11:03pm

amberwolf wrote:
May 01 2021 10:41pm
Regen current is probably battery amps of negative current, and is a limit to prevent damaging a battery from overcharging current, as well as to allow you to limit the max braking torque you may get.
So how much regen current can I start safely with?

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Re: Regenerative braking help?

Post by Eastwood » May 02 2021 11:27am

amberwolf wrote:
May 01 2021 10:41pm
If you have no ebrake wires from the controller either as a pair for a switch for on/off braking or as a triple for a second throttle for variable braking force,
So I ordered some momentary push buttons that I’ll connect to the break cut off switch. I guess in my thinking since I’ve never used region I just assumed there would be separate wires but now it makes sense that you activate the region through the actual break cut off switches.

Does this sound right?

Thank you for your help Amberwolf and contributing to this form! :wink:

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Re: Regenerative braking help?

Post by amberwolf » May 02 2021 11:44pm

Eastwood wrote:
May 01 2021 11:03pm
amberwolf wrote:
May 01 2021 10:41pm
Regen current is probably battery amps of negative current, and is a limit to prevent damaging a battery from overcharging current, as well as to allow you to limit the max braking torque you may get.
So how much regen current can I start safely with?
You have to check the charging current limit for your battery first. That's the primary limitation (so you don't damage the FETs in the BMS, assuming it is a single-port type, where charge and discharge happen from the same connector, or rather, from the same wire on the BMS, and so you don't damage the cells, though that is not that likely even with higher than normal regen charge currents, simply because that's typically only a second or two, unless you are regenning down a hill, in which case the cell limits apply too).

Then you can lower from there to suit the braking force you want.

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Re: Regenerative braking help?

Post by amberwolf » May 02 2021 11:47pm

Eastwood wrote:
May 01 2021 11:00pm
amberwolf wrote:
May 01 2021 10:41pm
If you have no ebrake wires from the controller either as a pair for a switch for on/off braking or as a triple for a second throttle for variable braking force,
The controller has ebrake wires. So would I connect a throttle to the E brake wires or maybe a momentary button to try and activate the regen?
If it is a pair of wires, a throttle won't work. That only works if it is designed for one, in which case it typically has three wires. So a momentary button, like those on "e" brake levers, or any brake lever that has a switch for brake lights, etc., or a pushbutton somewhere else (not very useful for typical in-traffic braking though, only for planned braking in advance).

For a switch that's useful for typical braking, it should be activated by moving the brake lever itself, or by your finger already on the lever. There are many ways to do this, if thats' what you want I can describe some.

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Re: Regenerative braking help?

Post by amberwolf » May 03 2021 12:01am

Eastwood wrote:
May 02 2021 11:27am
amberwolf wrote:
May 01 2021 10:41pm
If you have no ebrake wires from the controller either as a pair for a switch for on/off braking or as a triple for a second throttle for variable braking force,
So I ordered some momentary push buttons that I’ll connect to the break cut off switch. I guess in my thinking since I’ve never used region I just assumed there would be separate wires but now it makes sense that you activate the region through the actual break cut off switches.

Does this sound right?
The brake wires (whether for switch or for throttle) on a controller are what it uses to know you are braking. So that's also what it uses to determine when to apply regen braking, if it is capable of it (not all are), UNLESS it is designed in some other way, like the Grinfineons of the present generation. That, and the phaserunner/baserunner, are the only ones I can think of offhand that are like that (though some high-end ones are programmable to set them up any way you want, like Sevcon).

In those, there are ebrake wires, which will both shut off the motor and apply 50% of max regen power (not programmable). However, it's really designed to be controlled from the throttle wires--above 0.8v up to about 4v is throttle motor power control, and from 0.8v down to 0.0v controls the regen strength. This could be done with a physical throttle mechanism, but the typical ones don't do that, and I don't know of any commercially available ones that do either. So the Cycle Analyst v3 is designed to detect that you are pulling the brake lever, and then alter the throttle's functionality from outputting the motor power control voltage range to then output the regen control voltage range.

Since I find it completely unintuitive and impossible in an in-traffic braking situation for me to use the throttle to control braking force, when a brake lever is already there to do that *and* you have to pull it anyway to start the process, I just built a system that uses a brake lever to pull a cable-operated throttle just for braking, and a relay set that is turned on by the ebrake switch. The relays do three things: switch on the CA's ebrake input so it knows to send the 0.8v-0.0v range instead, switch on the brake lights, and switch the CA's throttle signal input from the actual motor power throttle over to the brake throttle. Thus, pulling the lever controls the amount of braking force...just like it would mechanically. :)

If you have to have a cable-operated brake at the same time, such as to hold your position on a slope while stopped, etc, there are dual-pull levers (though they don't typically have ebrake switches, those are easy enough to add), with an adjuster for each cable to setup tension such that the regen brake pulls all the way on before the mechanical brake begins to engage (or so they overlap as little as possible, unless you need the force of both brakes on that wheel at the same time).

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Re: Regenerative braking help?

Post by E-HP » May 03 2021 1:12am

amberwolf wrote:
May 01 2021 10:41pm
If you have no ebrake wires from the controller either as a pair for a switch for on/off braking or as a triple for a second throttle for variable braking force, then the only other way it could work is "slip regen", where when you roll off the throttle (rather than letting it go completely) it attempts to brake the motor to match the new speed or torque level. Letting it go completely simply cuts power but doesn't brake, for most ocntrollers in this mode.
I think some controller refer to it as "slide regen", which I use, and it doesn't cut power when letting go, just max braking. I've gotten used to it, and like it when I'm riding technical/tight turns, or riding off road, since I only really need to hit the brakes if it's a steep downhill, or if I need to come to a complete stop. I have a button that applies about 50W to the motor, that let's the bike "coast", but I'm so used to using the throttle, that I can "coast" by using my throttle to apply around 50W. It's funny how your throttle hand can learn and manipulate the throttle with very small movements, even with a cheap hall based throttle. I like it, but not for everyone. I've started using PAS on my bike again, so I just use the throttle method when I stop pedaling, to allow the bike to coast.

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Eastwood   100 W

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Re: Regenerative braking help?

Post by Eastwood » May 03 2021 6:32am

amberwolf wrote:
May 02 2021 11:44pm
You have to check the charging current limit for your battery first. That's the primary limitation (so you don't damage the FETs in the BMS, assuming it is a single-port type, where charge and discharge happen from the same connector, or rather, from the same wire on the BMS, and so you don't damage the cells, though that is not that likely even with higher than normal regen charge currents, simply because that's typically only a second or two, unless you are regenning down a hill, in which case the cell limits apply too).

Then you can lower from there to suit the braking force you want.
OK great to know! Yeah that’s what I was thinking that no more than the normal charging current.
amberwolf wrote:
May 02 2021 11:47pm
For a switch that's useful for typical braking, it should be activated by moving the brake lever itself, or by your finger already on the lever. There are many ways to do this, if thats' what you want I can describe some.
OK that makes sense. My first thought is to put the push button directly over top of the thumb throttle so I can switch from thumb throttle to E break quickly. I bought a couple different small momentary push buttons to try out and was going to fabricate a small mount. I’ll include a picture of where I was thinking of putting the push button

BUT... I like the idea of possibly installing it on the brake lever like you mentioned above. That would be great if you can describe some of the different ways people do this.

I have the magnetic cut off brake switches to use but I really don’t prefer those things because they’re so finicky. Seems like some type of small momentary pushbutton would be simpler and cleaner, more importantly functional.
amberwolf wrote:
May 03 2021 12:01am
from 0.8v down to 0.0v controls the regen strength.
OK good to know!!
amberwolf wrote:
May 03 2021 12:01am
Since I find it completely unintuitive and impossible in an in-traffic braking situation for me to use the throttle to control braking force, when a brake lever is already there to do that *and* you have to pull it anyway to start the process, I just built a system that uses a brake lever to pull a cable-operated throttle just for braking, and a relay set that is turned on by the ebrake switch. The relays do three things: switch on the CA's ebrake input so it knows to send the 0.8v-0.0v range instead, switch on the brake lights, and switch the CA's throttle signal input from the actual motor power throttle over to the brake throttle. Thus, pulling the lever controls the amount of braking force...just like it would mechanically. :)
Nice, Sounds like you got it dialed in perfect! Seems very practical having the region activated by the actual brake lever.
amberwolf wrote:
May 03 2021 12:01am
If you have to have a cable-operated brake at the same time, such as to hold your position on a slope while stopped, etc, there are dual-pull levers (though they don't typically have ebrake switches, those are easy enough to add), with an adjuster for each cable to setup tension such that the regen brake pulls all the way on before the mechanical brake begins to engage (or so they overlap as little as possible, unless you need the force of both brakes on that wheel at the same time).
I’m running hydraulic brakes so need to come up with something. Like I mentioned I have those magnetic cut off switches on hand but I really despise those things :lol:
Seems like the pushbutton could be installed on the actual lever or something along those lines.
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Eastwood   100 W

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Re: Regenerative braking help?

Post by Eastwood » May 09 2021 7:07pm

amberwolf wrote:
May 02 2021 11:44pm
You have to check the charging current limit for your battery first. That's the primary limitation (so you don't damage the FETs in the BMS, assuming it is a single-port type, where charge and discharge happen from the same connector, or rather, from the same wire on the BMS, and so you don't damage the cells, though that is not that likely even with higher than normal regen charge currents, simply because that's typically only a second or two, unless you are regenning down a hill, in which case the cell limits apply too).

Then you can lower from there to suit the braking force you want.
So I got the region and E-break function working 👍 thanks for the help!
The E brake function works with a momentary switch and the region starts working when I let off the throttle.

Also my discharge wires from the battery are separate from my charger port. So the region is not going through the BMS but my controller cuts the region when the battery is full.
Thanks!

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Eastwood   100 W

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Re: Regenerative braking help?

Post by Eastwood » May 15 2021 6:58pm

So if you have the E brake set to say 50a, how long can you hold that going down hill before it hurts the battery? Or is that even a concern? 🧐

My region is not going through the BMS as their separate discharge wires. The controller is set to cut the region when the battery is full.

Thanks!

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