Motor/regen braking only works in high speed? (14kmh and above)

[Etni]

Hello!

I have a 26" 1500W hub motor and KT-LCD8H display, and I installed a controller that supports regen (kt 48svprl-sls02g), hoping that I could use the brake lever for motor braking.

The brake lever now works, and I can adjust the braking strength with setting C13, but even on the strongest setting it only brakes down to about 14km/h. Using the throttle speed control, I can slow down to about 8-10km/h before the brake cuts off, so the motor can do that, at least.

Is the lowest motor braking speed somehow adjustable? Or is it just a feature of the controller that I have to live with?

I know it'd make no difference in energy savings. I'm asking because I'd like to brake primarily with the motor, having mechanical brakes only as a failsafe (they're crappy rim brakes, I can't install discs on this bike).

 

[AHicks]

It's very likely working as well as it's going to. For whatever reason, there's a huge misunderstanding regarding the effectiveness of regen braking. It's WAY over rated. Most that don't live in an area with big hills find it completely useless. Those that do live in bigger hills learn that at best, it's only going to prevent you from building up a big head of steam. It's NOT going to stop you.

And yes, it's only going to work at higher speeds.

I would caution that I've read where some have had troubles using regen with fully charged batteries, e.g. encountering a big hill as you are leaving home. The controller and/or BMS are going to prevent charging as the battery is already charged. That leaves few places for the power your motor is generating (via regen) to go, which can result in mysterious failures....

 

[Etni]

Yes, no brakes with a 100% full battery is one drawback, no brakes in case of any motor/controller failure or disconnect is another.

But, based on my experience with electric boards and other vehicles, powerful motor braking seems very much possible. It can also be done at very low speeds by using (reverse) power rather than regenerating power. But I suppose such features aren't in high demand with bicycles, and I'll take your word for it that this KT bicycle controller just won't do better than what it already does. Thanks for the answer!

 

[E-HP]

My KT controller stops regen at 6mph. My Power Velocity controller stops around the same speed, maybe 5.5mph. Above 82V, I still have regen, but you can feel it pulsing if going down a steep hill, but never cuts out. If you set your regen too high, your motor will get hot. Even with the low setting I use, with a 1 mile, 900ft descent at 20%, I can watch the temp rising almost like it does while climbing.

 

[Etni]

My KT controller stops regen at 6mph.

That sounds more useful than mine. What's the model of your KT controller?

 

[Chalo]

I'm asking because I'd like to brake primarily with the motor, having mechanical brakes only as a failsafe (they're crappy rim brakes, I can't install discs on this bike).

Have you considered using rim brakes that aren't crappy? That's your best bang for the buck, and the most reliable braking system you can have on your bike.

 

[AHicks]

Yes, no brakes with a 100% full battery is one drawback, no brakes in case of any motor/controller failure or disconnect is another.

But, based on my experience with electric boards and other vehicles, powerful motor braking seems very much possible. It can also be done at very low speeds by using (reverse) power rather than regenerating power. But I suppose such features aren't in high demand with bicycles, and I'll take your word for it that this KT bicycle controller just won't do better than what it already does. Thanks for the answer!

RE:"electric boards and other vehicles" the issue on bikes, unless you are talking about the gear driven GMAC (that work fabulously) is low motor rpm.

 

[Audisport09]

It's very likely working as well as it's going to. For whatever reason, there's a huge misunderstanding regarding the effectiveness of regen braking. It's WAY over rated. Most that don't live in an area with big hills find it completely useless. Those that do live in bigger hills learn that at best, it's only going to prevent you from building up a big head of steam. It's NOT going to stop you.

And yes, it's only going to work at higher speeds.

I would caution that I've read where some have had troubles using regen with fully charged batteries, e.g. encountering a big hill as you are leaving home. The controller and/or BMS are going to prevent charging as the battery is already charged. That leaves few places for the power your motor is generating (via regen) to go, which can result in mysterious failures....

Whaat...respectfully I disagree Forget about the energy back. Regen with the right controller is absolutely mint... I won't ride a bike without it. I can barely remember the last time I used manual brakes. I have a BAC8000 and it can LOCK the rear wheel and bring me to a DEAD stop. Arguably more powerful than my hydraulic brakes, caution has to be exercised. The OP needs to change his controller, regen is programmed differently on some controllers. I know with sabvonton it will only slow you down to about 3mph and then it stops working. I think it is for safety, to stop you from locking your rear wheel and sliding out. Unfortunately this setting/safety feature can not be changed on most controller. Only controller I know of which you can change is the ASI. I'm sure there are others.

 

[scrambler]

My experience with regen is that it can indeed provide very strong braking power, but it all depends on the combination of motor, controller and battery.

A controller like the Silixcon gives you a lot of options for that.
- Regen on throttle cutoff (good for engine brake feel), and or on/off Switch (good for brake lever regen) and or variable regen lever
- Different levels for each regen for each power map.
- A max current for battery charging, so that regen cannot overload the battery
- A max current for phase amp regen. This can be higher than the max battery charge current, as depending on speed the phase voltage can be lower and allow very strong regen without exceeding battery current.
Because of this you can actually get very strong regen at low speed if you like.
- A cut off speed for the regen on throttle, so you keep some freewheeling at low speed if you like.
- Different regen level based on speed for throttle cutoff regen

Now obviously the first parameter (max battery charge current) is the ultimate limitation of how much regen you can get. If your battery configuration as a low max charge current, you cant exceed that...

 

[AHicks]

OK, I'm up for a little schoolin!

Assuming we are talking about this setup (26" 1500W hub motor and KT-LCD8H display), the one mentioned in the first post, I'd like to hear a little more about ideas that might enable enough regen to lock up the rear wheel.

Or were the 2 of you mentioning a totally different setup that shares none of the components mentioned? Is this type of performance available on 48v? What about the typical 1500w motor you might expect to see in a low priced conversion package?

 

[scrambler]

I was indeed talking about a totally different setup hence the reference to the Silixcon controller.

I do not know anything about that setup in particular, but in order to figure out what is the max regen it could take, I would start with the exact battery configuration (xS-yP) and the cells being used, so we could know the voltage and max charging current of the battery.
Next would be to review what are the controller options relative to regen

 

[Audisport09]

OK, I'm up for a little schoolin!

Assuming we are talking about this setup (26" 1500W hub motor and KT-LCD8H display), the one mentioned in the first post, I'd like to hear a little more about ideas that might enable enough regen to lock up the rear wheel.

Or were the 2 of you mentioning a totally different setup that shares none of the components mentioned? Is this type of performance available on 48v? What about the typical 1500w motor you might expect to see in a low priced conversion package?

A fair point, he is probably running like a 20a controller which really doesn't cut it. That is why I said the OP needs to change controller if he really wants to experience good levels of regen. The display matters not. Mainly my argument was regen is not overrated IMO and can be a wonderful feature to an ebike. I've run a 1000w hub with a Sabvoton, and could get plenty stopping power down to about 2-3mph, then I had to use brakes. Right now I have a BAC + QS205 = stops on the dot.

 

[Etni]

OK, I'm up for a little schoolin!

Assuming we are talking about this setup (26" 1500W hub motor and KT-LCD8H display), the one mentioned in the first post, I'd like to hear a little more about ideas that might enable enough regen to lock up the rear wheel.

In my case (OP) the brake at max setting is too strong for me to use at high speed, because with this controller the brake is just 2 wires, on/off. I’d imagine some other controllers have 3 wires and can adjust braking strength based on lever position.

Anyway, the max setting almost throws me off the bike, so no problem about braking strength - the issue is that it tapers off to about 14km/h and doesn’t go slower than that.

 

[scrambler]

OK, I'm up for a little schoolin!

Assuming we are talking about this setup (26" 1500W hub motor and KT-LCD8H display), the one mentioned in the first post, I'd like to hear a little more about ideas that might enable enough regen to lock up the rear wheel.

In my case (OP) the brake at max setting is too strong for me to use at high speed, because with this controller the brake is just 2 wires, on/off. I’d imagine some other controllers have 3 wires and can adjust braking strength based on lever position.

Anyway, the max setting almost throws me off the bike, so no problem about braking strength - the issue is that it tapers off to about 14km/h and doesn’t go slower than that.

Having a variable regen would require the controller to be able to handle it.
But even if the controller only handles on/off, it may / should have various setting that could help, like different level of regen for different speed, low speed cutoff, and of course max regen.
In both cases, worth investigating what programmability the controller has.

 

[Etni]

]

In both cases, worth investigating what programmability the controller has.

Well that’s why I asked - because I’ve gone through the settings and haven’t found anything obvious besides C13.

 

[AHicks]

[youtube][/youtube]

In both cases, worth investigating what programmability the controller has.

Well that’s why I asked - because I’ve gone through the settings and haven’t found anything obvious besides C13.

Pretty familiar with the KT, and it's an on/off arrangement using one of 5 presets. That's it to my knowledge.

 

[E-HP]

[youtube][/youtube]

In both cases, worth investigating what programmability the controller has.

Well that’s why I asked - because I’ve gone through the settings and haven’t found anything obvious besides C13.

The on/off regen from stock KT controllers is better suited for regen to the battery than braking. That goes for any on/off/digital regen due to lack of control of the braking force. (you only need to go down a steep wet curve in the road with regen set too high to figure that out). On/off is still good to supplement regular brakes. Regen to the battery works best at low regen settings, in order to NOT slow down the bike too quickly (bike needs to be moving to provide regen).
Some KT controllers can be upgraded with Open Source firmware that enables variable regen. Some soldering is involved to provide the connections for a second throttle to use for braking. You could also modify a brake lever to make a hall sensor based brake lever for variable regen:
https://www.youtube.com/watch?v=gE2KvwUhD1w&t=1s
Otherwise, switch to a controller that supports it out of the box.

 

[amberwolf]

You could also modify a brake lever to make a hall sensor based brake lever for variable regen:
https://www.youtube.com/watch?v=gE2KvwUhD1w&t=1s

FWIW, if you don't want ot or can't put hte hall sensor and magnet at the lever, you can use the lever to pull the cable of a cable-operated throttle instead:
https://endless-sphere.com/forums/viewtopic.php?t=105460
Main disadvantage is the COT is rather large and you need a place to put it...but it is "waterproof" (at least, mine, exposed on the steering tiller tube, have had no issues in the drenching/flooding rains we get a few times a year, that I always seem to be riding in when they happen).

Other disadvantage is needing a brake lever dedicated to just this cable, or using a dual-cable-pull lever (one for your brake, one for your COT).

 

[Etni]

Some KT controllers can be upgraded with Open Source firmware that enables variable regen. Some soldering is involved to provide the connections for a second throttle to use for braking. You could also modify a brake lever to make a hall sensor based brake lever for variable regen:
https://www.youtube.com/watch?v=gE2KvwUhD1w&t=1s

Awesome! Thanks a lot for the link, I’ll look into this.