Help me pick a motor for my 26x3", 150mm dropout DH bike (goal 35mph)

[stanson]

So my dh bike has 26x3" wheels with 155mm dropouts. I wanted a 1500-2000w motor so I could cruise around 33mph on a 52v lith ion, and hit 40mph on a 18s lipo on short occasions for fun.

I do not want to get a big power hungry 3000w motor, as I dont want to upgrade to a more expensive 72v battery and controller at this moment. I am planning on using my 52v battery, and I was under the impression using a power hungry motor with a small 52v battery will result in terrible range and battery stress. (edit: see comments below, looks like I'm prob. incorrect on the stress part)

Does anyone have recommended wide hub motors (and north american vendors) in the price range of 200-400$?


**
ebikes.ca got back to me first. They sent me the DD45_FST model, which can be used on 135mm-155mm dropouts. The motor is rated for 1000-2000w and costs $300.

QS Motors responded today, I was really impressed with the email they sent me. They included a really convenient spread sheet that listed requirement to get to 40mph. They set me up with the QS 205 V2, 2000w and around 180$? Plus a 100amp controller for 150$. This so far seems like the best bang for my buck.

*So I am being told now, that I can use a 135mm motor hub as long as the axle comes out wide enough to extend past my frame. Apparently the QS V1 is for 135, but it has 200mm axles, which are long enough to fit in my bike. I just need to find spacers to make up for the extra space in between, which Im being told isnt hard.

 

[Grantmac]

Have you considered a mid-drive?

 

[stanson]

I was under the impression that the the mid drive kits available here (luna cycle cyclone 3000w and the bafang BBSHD) are both not well suited for the top speeds I was hoping to hit.

I was also under the impression that there was a decent chance of stripping the internal gears when throwing 72+ V's at them. Also, more "moving parts" that were prone to failure if alignment is off (chains not staying on, skipping etc).

But to be honest, I am starting to consider it more now that I'm finding standard motor hubs to be too small...

If Luna cycle offers a good warranty on the cyclone, I guess stripping gears shouldnt really be too much of a concern anyways.

 

[Chalo]

Do you understand that motor power is limited to what the controller feeds in?

The power ratings of motors are what they are supposed to be able to produce continuously under nominal conditions. If you give them less voltage than their ratings, they'll run slower. With less current, they produce less torque. Either way, that's less power.

 

[stanson]

Do you understand that motor power is limited to what the controller feeds in?

The power ratings of motors are what they are supposed to be able to produce continuously under nominal conditions. If you give them less voltage than their ratings, they'll run slower. With less current, they produce less torque. Either way, that's less power.

Correct me if I'm wrong here, matching a high power motor, like a Mxus 3k turbo, with a small battery (48 or 52v) and controller (30 amp) is not ideal and can lead to battery or controller damage?

I was under the impression that having a high power motor required high powered batteries. I thought that the draw from the motor could pull more power from the controller and batteries then they were meant to discharge, causing the battery to be stressed or overdrained. Is this not a thing to worry about?

But, that leads me to another question:

Does a 1000w cheap ebay motor traveling @20mph have the same range as a high power mxus 3k motor running @20mph with the same battery? (lets say 52v 20ah). If the mxus 3k is a power pig, and sucks up twice the wattage as the cheapo kit, you can see why I'd want to avoid the big motor, as its overkill.

 

[Chalo]

The controller will draw only as much current as it's capable of transmitting. Usually it's the controller that dictates the maximum power of a battery + controller + motor system. Ideally, both the battery and the motor can tolerate higher power than the controller, and thus those more expensive components are worked well within their limits.

 

[amberwolf]

I do not want to get a big power hungry 3000w motor, as I dont want to upgrade to a more expensive 72v battery and controller at this moment. I am planning on using my 52v battery, and I was under the impression using a power hungry motor with a small 52v battery will result in terrible range and battery stress. (correct me if im wrong, I may be imaging this theory?)

The motor "wattage" isn't the problem you'd run into.

It's the controller current rating.

The higher wattage the motor is, simply means it is *capable* of higher continuous (and usually peak) power if you did need it, simply by using a controller with similar capability.

If you are using a controller that is matched to your battery's capabilities, at the lower current, then it'll still drive a bigger motor. It just won't be using the motor's full capabilities.


If you start with teh smaller motor, then decide you want more power, you now have to buy a new controller, battery, *and* motor, instead of just the controller and battery.

 

[Grantmac]

I was under the impression that the the mid drive kits available here (luna cycle cyclone 3000w and the bafang BBSHD) are both not well suited for the top speeds I was hoping to hit.

I was also under the impression that there was a decent chance of stripping the internal gears when throwing 72+ V's at them. Also, more "moving parts" that were prone to failure if alignment is off (chains not staying on, skipping etc).

But to be honest, I am starting to consider it more now that I'm finding standard motor hubs to be too small...

If Luna cycle offers a good warranty on the cyclone, I guess stripping gears shouldnt really be too much of a concern anyways.

Is your intent proper offroad riding or just very smooth trails?

You won't damage anything internal on a Cyclone even running 4kw. It's the bicycle components that take the beating.

 

[stanson]

Is your intent proper offroad riding or just very smooth trails?

You won't damage anything internal on a Cyclone even running 4kw. It's the bicycle components that take the beating.

My primary use is for a commuter bike, ideally ~20 miles a charge cruising at 30mph on mostly flat streets. If I ever even did take it off road, it would be smooth trails.

It seems like the only motors that fit 150mm drop outs are bigger, power hungry motors, and there isnt really a way around it. I have been looking at thread on axle extenders, but that tech doesnt seem to reliable. I'm really feeling defeated here.

The only way I can afford to get a battery that can feed those motors, is to get lipo it seems like.

I have my eye on 20ah 4s packs from HK for only 120 a piece. Thats $480 for a 20ah 60v lipo pack. Not a bad price at all!

 

[stanson]

The controller will draw only as much current as it's capable of transmitting. Usually it's the controller that dictates the maximum power of a battery + controller + motor system. Ideally, both the battery and the motor can tolerate higher power than the controller, and thus those more expensive components are worked well within their limits.

Well I talked to a high power bike builder today. He has built many bikes with the QS and Mxus motors and I've seen many of his videos on youtube. When I mentioned that I wanted to use a triangle 52v battery from UUP on ebay, he told me to avoid that, as the "3k motors draw will trip the cheap ebay batteries BMS almost immediately." He said I needed 60v to operate it.

What is your take on this? Now I am REALLY feeling confused

If I do get a bigger motor, like the QS 205 v2 (2000-3000w), I am now assuming it would be better to get 4 of these lipos: 4s, 20ah, 4 together to make a 20ah 60v pack for only $480 dollars. I cannot even fit a 52v triangle UUP battery on my frame, so its looking like this is the way im starting to lean to

 

[Grantmac]

If offroad performance and extreme hill climbing doesn't matter then any hub which fits should be fine. You should be able to dial in reduced battery amps on an programmable controller.
Conversely if you are diligent in monitoring you can use those Lipos.

 

[amberwolf]

Well I talked to a high power bike builder today. He has built many bikes with the QS and Mxus motors and I've seen many of his videos on youtube. When I mentioned that I wanted to use a triangle 52v battery from UUP on ebay, he told me to avoid that, as the "3k motors draw will trip the cheap ebay batteries BMS almost immediately." He said I needed 60v to operate it.

No, you don't.

You are still confusing the motor with the controller.

The controller controls how much power the motor gets.

The motor does not control how much power the system gives it.

(it is slightly more complicated than that, but that is the basics.)

You can use a motor capable of much higher power, at very low power.

If you could not, you could not control it's speed or torque and it would always just be at full power all the time regardless of what you want.

Use the battery and controller you already have on the bigger motor, until you decide you want to *use* the capabilities of the bigger motor.

To better understand all this, please go to http://ebikes.ca/simulator, and read up on the instructions/etc below it, so you'll know what you are seeing in the chart at the top.

Then experiment with different motors, but with the same controller and battery. In general, if the motor has the same basic winding, it will run about the same speed in the same wheelsize, all else the same of the system and terrain and weather conditions. Then try the bigger motors with a higher current controller, and/or a higher voltage battery.


I am using *two* MXUS3Ks (20" wheels) on SB Cruiser trike, usign a "52v" (14s) battery, with a couple of generic "30A" controllers. Works just fine, and on a lightweight ebike (which the trike is not, by far) it'd probably be pretty impressive acceleration and power just at that.

I later modded one of the controllers for about 80A, and it significantly improved the startup power. Later swapped out the other "30A" contgroller for a "40A" controller, and improved it even more.



Keep in mind that to get the speed you want you might have to upgrade your controller or battery to reach or maintain higher speeds, if those speeds under the weather and terrain conditions you have take more power than they can handle. But that doesn't have anything to do directly with the motor being bigger or smaller.

 

[amberwolf]

QS Motors responded today, I was really impressed with the email they sent me. They included a really convenient spread sheet that listed requirement to get to 40mph. They set me up with the QS 205 V2, 2000w and around 180$? Plus a 100amp controller for 150$. This so far seems like the best bang for my buck

Keep in mind that a 100A controller at 52v (for your existing battery) is basically a 5KW controller, so it can suck a smaller battery dry and overload it easily. So you'd need to buy a battery that could handle that, too, unless the controller is programmable to match your existing battery.

 

[999zip999]

What battery do you have now ? The big question. Link. I have a 1,500watt edge. Frist one had metal in between the cover and bearing it split out and the noise when away. open it up and found a purple ring in the cover. Then melted the magnets off. Looked like black power holding them down. 72v 40amp battery. I don"t think they sale them any more. Check out a Leaf motor.

 

[stanson]

What battery do you have now ? The big question. Link. I have a 1,500watt edge. Frist one had metal in between the cover and bearing it split out and the noise when away. open it up and found a purple ring in the cover. Then melted the magnets off. Looked like black power holding them down. 72v 40amp battery. I don"t think they sale them any more. Check out a Leaf motor.

So I am still holding off on buying my battery, but I am pretty sure I have narrowed it down to running 4, 4s lipos in series to make a 16s (60v) 20ah battery. Was ready to pull the trigger, but I am realizing now, that I am not educated enough about how to charge these high cap lipos. I need to figure out what power supply and charger I'll be needing that is reasonably priced and can charge somehwat quickly.

Currently I am deciding between the QS 205 V1 or the QS205 V2.

Thanks for the input!

 

[Chalo]

When I mentioned that I wanted to use a triangle 52v battery from UUP on ebay, he told me to avoid that, as the "3k motors draw will trip the cheap ebay batteries BMS almost immediately." He said I needed 60v to operate it.

What is your take on this? Now I am REALLY feeling confused

If you use the controller that comes with a 3kW motor, yes the current demand will trigger the battery's protection. But if you use a controller that maxes out at a lower current than your battery's rating, then everything is happy. (You just won't get 3kW from your motor.)

To be honest, a generic 18650 pack isn't what I'd use for a 2kW or 1500W controller either. I'd try to find a battery rated for at least double the current of your controller.

 

[999zip999]

QS has a list of motors that they can make. Some they only make with big order.