Regenerative braking question (KT-LCD5)

[ProgramThyself]

I have a Firefly attachment (https://riomobility.com/firefly/) for a wheelchair that uses ebike components for the drive. It is basically a front-wheel drive tricycle. The display is called KT-LCD5 (similar to LCD3), the system uses a 36 V battery with the motor controller integrated in the base, and the motor is labeled 350 W. Maximum speed is 24 km/h. The motor can go forwards and backwards and seems to be a "geared" type with no clutch.

Several posts on this forum state that regenerative braking can cause reliability problems, including loosening of the axle nuts, which I am experiencing (https://ffuser.blogspot.com/2019/06/axle-creak.html).

My question is whether motor-braking can be disabled for increased reliability? The display manual is available online (https://download.elecycles.com/manual/Display-Manual/LCD5-display.pdf).

However, the as-delivered and current setting for parameter C13 is already 0, meaning "No ABS brake" (page 35). Yet, when I'm cruising and reduce the throttle, the motor causes noticeable braking. Letting go of the throttle completely makes the vehicle coast with no motor brake. I'm trying to figure out whether this motor-brake is the same thing as the "regenerative braking" that is often discussed, and whether there is a way to turn it off.

FYI, the throttle is in "imitation torque mode" (P3 = 1), but behavior in "speed control mode" (P3 = 0) has similar motor-brake behavior. I could try C13 = 1, just to see the difference in behavior, but don't want to damage anything given the bold-face warning. Does anyone understand these settings?

 

[amberwolf]

There is a function in some controllers called "slip regen" that does what you describe--it will attempt to hold either the torque or the speed set by the throttle.

So if you reduce throttle, it will reduce the speed of the motor by applying braking until speed is at the demanded level, or reduce the torque of the motor by applying negative torque (braking) until torque is at the demanded level, depending on the type of throttle control the controller uses.


Unless there's a way to disable this function, then AFAIK you'd have to change the controller out to fix it. Or use Casainho's / Stancecoke's et.al. open source firmware which prob ably lets you do whateer you want.


HOwever, you can also just use good torque arms on the axle, which correctly mounted will prevent looseningof the axle nuts and wiggling of the axle, so you don't have to disable this useful feature.

 

[ProgramThyself]

Thanks for the tips about "slip regen" open-source FW. They are topics to explore. Anyway, I changed the parameter for "ABS braking" (C13) to see what happens. It has no discernible effect on the throttle behavior. Instead when I apply the mechanical brakes now, the battery bars on the LCD display become animated to show regeneration. Presumably, the C13 = 1 option causes regen braking to kick in when mechanical braking is detected (this is sensed in the cable harness). So maybe my question is more about throttle behavior, and less about regenerative braking.

How can I prevent the throttle causing backwards torque?

I understand how a speed-mode throttle would apply reverse torque to lower the speed when the throttle decreases from the max. But In my mind, a proper torque-mode throttle wouldn't apply reverse torque when I back off the maximum. It would just push the motor forwards less. Maybe it's called "simulated torque mode" in the manual to distinguish from a more accurate mapping between throttle and torque.

There isn't much extra length on the axle for torque arms, and I don't believe they would absorb all of the stresses that occur when the motor cycles repeatedly between forwards and backwards torque due to throttle variations that are often minor. The motor gear teeth will also cycle between being loaded hard on the forwards and backwards faces. And there is a frame attachment point that noticeably flexes with acceleration/deceleration. Yes, it will also flex when decelerating due to braking, but there are many more cycles due to minor throttle changes that result in motor torque reversal. I wouldn't mind changing brake pads more often if it increases vehicle reliability...

 

[amberwolf]

How can I prevent the throttle causing backwards torque?

Assuming it is the controller doing it, you'd have to find out how to disable the slip-regen mode. That's what the behavior you're seeing is called, most often. I can't find anything in the linked manual about it.

One other possibility is that the geared hub, due to the gear ratio (usually around 5:1), is actually just producing a large amount of drag whenever it is not powered. It will produce five times the amount of drag a DD hubmotor of the same winding does, because of the 5:1 reduction. If the reduction is greater, then so is the drag.

As a test, disconnect the phase wires of the motor from the controller, (noting how they were connected if they are individual plugs, so they don't get mixed up), and try pushing the chair. if it is this problem, it will be quite diffcult to push. If it is not difficult to push, it is probably something in the controller itself.

Given that you don't have the drag if you just zero the throttle, it's most likely slip-regen mode of throttle operation causing it.

 

[endlessme]

OP. Did you find a solution yet?

I am facing the exact issue as yours. Example I going at speed 40km/hr then take your hands off on throttle and immediately resistence/regen kicks in thus slowing down the momentum. When you raise throttle again you will see motor moving forward and so much power is being used. I am not sure if that's from regen current.

 

[endlessme]

I have a Firefly attachment (https://riomobility.com/firefly/) for a wheelchair that uses ebike components for the drive. It is basically a front-wheel drive tricycle. The display is called KT-LCD5 (similar to LCD3), the system uses a 36 V battery with the motor controller integrated in the base, and the motor is labeled 350 W. Maximum speed is 24 km/h. The motor can go forwards and backwards and seems to be a "geared" type with no clutch.

Several posts on this forum state that regenerative braking can cause reliability problems, including loosening of the axle nuts, which I am experiencing (https://ffuser.blogspot.com/2019/06/axle-creak.html).

My question is whether motor-braking can be disabled for increased reliability? The display manual is available online (https://download.elecycles.com/manual/Display-Manual/LCD5-display.pdf).
Screenshot from 2019-06-21 12-44-06.png
However, the as-delivered and current setting for parameter C13 is already 0, meaning "No ABS brake" (page 35). Yet, when I'm cruising and reduce the throttle, the motor causes noticeable braking. Letting go of the throttle completely makes the vehicle coast with no motor brake. I'm trying to figure out whether this motor-brake is the same thing as the "regenerative braking" that is often discussed, and whether there is a way to turn it off.

FYI, the throttle is in "imitation torque mode" (P3 = 1), but behavior in "speed control mode" (P3 = 0) has similar motor-brake behavior. I could try C13 = 1, just to see the difference in behavior, but don't want to damage anything given the bold-face warning. Does anyone understand these settings?

I faced the exact same issue. Now, my problem is solved by setting correct values. Please see attached image and set value's according to your motor voltage. My motor is 48v1000w using KT controller with KT LCD3 display.





48V1000W Direct Drive. Max Speed 55Km/hr.

 

[ProgramThyself]

OP. Did you find a solution yet?

I am facing the exact issue as yours. Example I going at speed 40km/hr then take your hands off on throttle and immediately resistence/regen kicks in thus slowing down the momentum. When you raise throttle again you will see motor moving forward and so much power is being used. I am not sure if that's from regen current.

I'm not sure our issues are the same. Mine does coast properly with hands off the throttle. My problem comes from regen and resistance kicking in when I lower the throttle from say 50 % to 45 %. The controller keeps trying to make the speed track the throttle and I don't like how small unintentional thumb movements cause significant braking.

My solution is to try different motor controllers. Lately, I've been testing a VESC where the right throttle drives only forward, and the left one signals braking current and reverse. That's working pretty well, at least in dry weather Thanks for sharing your parameters. Here are mine (IIRC higher C5 may allow higher current):

 

[Samik]

Hello

I hope one of you can help me. I didn't really understood what you said and the tech questions as my English is just like it is
I changed lcd on my Rio firefly and with new, I lost reverse speed.
I searched, I have the manual but I'm not sure how you call the fact to press and have - 1 to go reverse, behind... Motor going backyard as I didn't not find clearly this in manual

Do you know what is the settings to do so?
I thought it was c13 by reading you but tested them all settings, not working

Thanks you!