Using RC motors on E-bikes [Archive]

[dirty_d]

why not design our own? make the schematic and pcb layout public, some people that have the abilitiy to make the pcbs could make them and sell them, then you just order the parts and solder it yourself. people who cant program a MCU you can do the same deal with, they can sell those pre-programmed too. i can see it being much cheaper than the rc controllers.

 

[recumpence]

The big issue, from what I have heard, is not the hardware, but software for startup and staying in sync.

I have alot of faith in the RC controllers, to a point. That point seems to be about 3,000 watts. If you stay under that threshold, there seems to be no issues. Above that, just make sure your power supply can handle it.

I remember this from my SPL competition days. A simple 300 watt amp was great. But a 500 watt amps would pulse your headlights. Hmm, 1,000 watts would actually dim the dash lights too. 2,000 watts would fry your alternator. Also, "Why are my big amplifiers blowing FETs?" Hmm, OK, lets go with 0 guage wire, 4 batteries, and four 1 farad caps right before the amp inputs. Next we go with a high amp alternator (or 2 or 3 or 4 :wink: ) Wow, all problems solved!

I think that is the wall I am running into right now. I am pushing for more and more power. I regularly pulled 5,300+ watts from my HV110 with substandard wiring and not enough capacitance as well as way too long wiring. Kknowing what I know now (or should have known with my audio experience), I am surprised my ESC lasted so long!

Anyway, I will have my new HV240 soon (as well as a bank of caps, better wiring, and new connectors).

We shall soon see how it runs! I am pushing for 7,000 watts.

Matt

 

[Miles]

Here's a link to the industrial versions of the Castle Creations HV controllers:
http://www.castlespecialprojects.com/csp_50_volts.html They give details of de-rating for different air flows.

There is a price premium for these versions but the software allows more control options:
http://www.castlespecialprojects.com/csp_software.html

 

[recumpence]

Yup, I am thoroughly familiar with them. they are not available untill winter, though.

Matt

 

[eP]

The big issue, from what I have heard, is not the hardware, but software for startup and staying in sync.

It is time and hardware/money consuming task. Someone who want to develop powerful and competitive ESC just for pleasure need to have powerful motor too for testing purposes at least.
And still such one person project is related with risk the other guys will choice comercially available brand ESC.

So my idea is not for creazy and brave enthusiast who is ready to spend many hours just for pleasure at such project, but for guys who already have powerfull motors or are really interested in such "toys". A few guys if they could join theirs very limited founds (relatively low risk) could start finance such project for pleasure and gains if it become succesful project.

 

[ZapPat]

This controller would have to be a pedal-first design, since Back EMF is only big enough to be measured and used at a certain motor speed. This is one fundamental difference between RC planes and bikes - reliable low speed operation is necessary for the bike.

I was wondering how hard it would be to assemble our own hall sensor setup inside the RC motor? I don't have one, but I would imagine it might be hard to find the room in there. The hall sensors make for good low speed operation, instead of the usual automated start up sequence used in sensorless controllers. Or just go for a pedal-first controller that starts up only at a minimal RPM...

What are your opinions on the subject?

 

[safe]

They just seem to need to be built bigger and stronger than this. 2" for their high powered version is great in an RC plane due to their space limitations, but for ebikes there's room to spread out a little more and use stronger parts.

 

[safe]

I know it's expensive, ($480 at ElectricMotorsport) but wouldn't one of these work?

250 peak amps.

http://www.sevcon.com/pages/millipakPMAC.html

PM AC Motor Controller
For motors to 4 kW

The Millipakâ„¢ PMAC controller operates in Trapezoidal or Sinusoidal waveform switching modes. Brushless PM motors offers absolute speed control that is hard to duplicate on a series motor without adding extra circuitry and costly speed probes, sensors or tacho generators. The Millipakâ„¢ PMAC brushless solution enhances system reliability and reduce warranty and maintenance costs.

Not only that, but it's programmable and even has this very advanced motor analysis software that could discover all the necessary information automatically so that you can configure things better.

The other option is just to abandon this quest for 4kw+ power and go back down to the 750 watt range, add the gears back in, and then use the smaller stock controllers. I'm sure the stock (cheap stuff) controllers would work just fine if kept down to 750 watts.

 

[eP]

The other option is just to abandon this quest for 4kw+ power and go back down to the 750 watt range, add the gears back in, and then use the smaller stock controllers. I'm sure the stock (cheap stuff) controllers would work just fine if kept down to 750 watts.

What 750 watt motor need more than 2 gears ( not for racing purposes ) ??

 

[MitchJi]

I'm still convinced the Optibike is on the right track... keep the power right around 750 watts and integrate the power with the pedals and the gears. That's all the power we need. Beyond that and we're really talking about motorcycles and not bicycles. The RC motor (high rpm motor) is simply an addition to the Optibike... an increase in focus on the main theme... towards this perfected system.

Hi,

And IMO the reasons RC motors contribute to this "perfected system" are lighter weight and more power. About 2kW, with gears seems good to me.

 

[Miles]

This controller would have to be a pedal-first design, since Back EMF is only big enough to be measured and used at a certain motor speed. This is one fundamental difference between RC planes and bikes - reliable low speed operation is necessary for the bike.

The latest sensorless controllers seem to have pretty good low speed control - I'm not sure it would necessarily have to be pedal-first.

 

[johnrobholmes]

The startup at zero RPM is very tricky. On something with as high of a speed range as we want, and as much weight as we need to move, the only way I can see sensorless startups from a stop is with a very low first gear.

For a no pedal startup I think we would really need a sensor. I have done a lot of testing on the startup thresholds of outrunners, and they get over geared easily just like any other sensorless design.

 

[nomad85]

I dont understand why everyone thinks these RC motors are the best solution.. it takes a bazillon amps to do anything. Fine if you use lipo, but most people arent comfortable with the risk, lifepo4 cant supply the power, unless you are loaded and can afford tons of A123. I only use 10-15 amps on my bike to go 28-30 mph. Also the gearing is very complicated, more parts=more to go wrong. And it seems to be really expensive. I think its an awesome concept with great performance potential, but its not practical. Seems more like a powerful toy(which might be what you are after) than an actual usuable communting vehicle. Just get a hub motor and some lifep04 and be done with it, practical and reliable, at least at 48v it is. and thats all anyone should really "need". Now if some better manufacturers started making hub motors we would really have it made.

 

[MitchJi]

This thread and the pioneers working on RC motors on ebikes has really got me excited.

One thing still troubles me however. Im still not convinced that these rc controllers are the way to go, they just don't seemed to be properly designed for our application. The Castle boat HV esc seems like a promising candidate but man it is expensive. What I would like to personally see is a ruggedized version of a high voltage ESC that works with regular ebike throttles, has current limiting built in, more caps and can handle spike, etc... or a least a way to hack something from available components. Most dont want to be frying ESCs on a regular basis, and hopefully Matt can get a sponsorship deal or at least a beta tester thing going as this is going to be a HUGE market in the near future.

I maintain my original theory that the ESCs are the weak link.

These ESC arent going in a rc plane, I would think we could add a few ounces for increased reliability/longevity.

Jeff, agreed.

The controllers are not built to drive a stalled motor who's resistance is less than .5ohm............. So you are going to see a limit but at least that limit will save the motor from melting down. As you say, whats needed is a ruggedized controller that can actually ramp down when it gets near its limit - the Power Jazz due to be with me in 2 days seems to promise that function albiet probably temperature activated.

I am not at all sure about the throttle thing - I set out to avoid one of those at all costs - way to many issues with water. I do hear magura make one that works but does it work underwater? Thats a serious question.

Having said that - right now I am having doubts about 3KW rc motor on a bike. Others run 6kw hubs without issues but I rather suspect that 6kw is a peak rating - the max it will ever pull (what is the resistance of the windings on a big CL?). My motor will pull over 200A (VIR) from a 24V source if its asked to deliver the goods, that means 5KW and on 36V you are looking at the best part of 8KW. So right now I am sitting on a bike thats out to kill me and I'm not at all sure I set out to create this.

The big issue, from what I have heard, is not the hardware, but software for startup and staying in sync.

I have a lot of faith in the RC controllers, to a point. That point seems to be about 3,000 watts. If you stay under that threshold, there seems to be no issues. Above that, just make sure your power supply can handle it.

Hi,

This is exciting to me too. Many thanks to everyone for the great information!

I'm not sure if this is a huge market or not. Hub motor systems are so much simpler to set up...

Is there a consensus that if we stay under about 3kW AND we use an ESC with good software for for startup and sync it will work reliably? If so does anyone know of an ESC or ESC's that has good software (hopefully there is a least one that is a little less expensive than the Power Jazz)? If so please post the name or names. Hopefully we can compile a list.

I don't see any advantage to an Ebike electric throttle as compared to a motorcycle cable throttle connected mechanically to the RC ESC or Servo Tester. I might be best to put a long lever on the ESC or ST but if done correctly this should work as well as a normal Ebike throttle and should be more reliable.

I hope to use an RC motor with more capacity than I use because that should be more reliable. Limit the watts I draw to something like 1.5kW or 2.5kW from a motor rated for 4kW.

You could make the argument that a 36V 3kW RC system is safer than a 72V 2kW CL system since the rule of thumb for lethal voltage is 48V. In any case I'm pretty sure I don't want to be riding a 72V Ebike in the rain.
Thanks Again!

Mitch

 

[Miles]

I dont understand why everyone thinks these RC motors are the best solution.. it takes a bazillon amps to do anything. Fine if you use lipo, but most people arent comfortable with the risk, lifepo4 cant supply the power, unless you are loaded and can afford tons of A123. I only use 10-15 amps on my bike to go 28-30 mph. Also the gearing is very complicated, more parts=more to go wrong. And it seems to be really expensive. I think its an awesome concept with great performance potential, but its not practical. Seems more like a powerful toy(which might be what you are after) than an actual usuable communting vehicle. Just get a hub motor and some lifep04 and be done with it, practical and reliable, at least at 48v it is. and thats all anyone should really "need". Now if some better manufacturers started making hub motors we would really have it made.

I'm not sure why you think they need more amps? LiFePo4, or even NiMH, can certainly have good enough power density.

Judging by all the posts on broken hub motors, sensor problems, breaking spokes, torque restraint problems.... maybe they aren't so practical....

 

[Miles]

Mitch,

All you have to do is use an ESC at below 80% of its rating and you won't have a problem.

The Castle Creation HV controllers are very good.

 

[ZapPat]

I know it's expensive, ($480 at ElectricMotorsport) but wouldn't one of these work?

250 peak amps.

http://www.sevcon.com/pages/millipakPMAC.html

PM AC Motor Controller
For motors to 4 kW

The Millipakâ„¢ PMAC controller operates in Trapezoidal or Sinusoidal waveform switching modes. Brushless PM motors offers absolute speed control that is hard to duplicate on a series motor without adding extra circuitry and costly speed probes, sensors or tacho generators. The Millipakâ„¢ PMAC brushless solution enhances system reliability and reduce warranty and maintenance costs.

Not only that, but it's programmable and even has this very advanced motor analysis software that could discover all the necessary information automatically so that you can configure things better.

The other option is just to abandon this quest for 4kw+ power and go back down to the 750 watt range, add the gears back in, and then use the smaller stock controllers. I'm sure the stock (cheap stuff) controllers would work just fine if kept down to 750 watts.

I have one of these on my first ebike build that I just completed a month or so ago. The sevcon now drives an old (but barely used yet) 4.5 kW ecycle motor that I have mounted on a steel-framed mountain bike. It has a double chain system using the stock crankshaft and gears, and has had the pedals removed. And 36V of good lead odysseys.

I managed to adapt this controller to my ecycle, but be warned that sevcon does not officialy support using this controler with any other motor than the mars brushless. They were not very informative people to deal with, I'm sad to say. You can however configure many things using there costly old-style configuration doodad called the calibrator.

However, since this discussion is about ebikes using RC motors, this would NOT be a good controller since it needs hall sensors to work. Anyone think we could add our own halls to RC motors? :?

 

[nomad85]

I dont understand why everyone thinks these RC motors are the best solution.. it takes a bazillon amps to do anything. Fine if you use lipo, but most people arent comfortable with the risk, lifepo4 cant supply the power, unless you are loaded and can afford tons of A123. I only use 10-15 amps on my bike to go 28-30 mph. Also the gearing is very complicated, more parts=more to go wrong. And it seems to be really expensive. I think its an awesome concept with great performance potential, but its not practical. Seems more like a powerful toy(which might be what you are after) than an actual usuable communting vehicle. Just get a hub motor and some lifep04 and be done with it, practical and reliable, at least at 48v it is. and thats all anyone should really "need". Now if some better manufacturers started making hub motors we would really have it made.

I'm not sure why you think they need more amps? LiFePo4, or even NiMH, can certainly have good enough power density.

Judging by all the posts on broken hub motors, sensor problems, breaking spokes, torque restraint problems.... maybe they aren't so practical....

Matt's bike pulls over 120 amps with the AXI motor, even more now. thats a lot. Properly setup, with modest voltage, I think hub motors are pretty reliable. not perfect though. Over volting(72+) seems to be where more problems happen. (We'll see how I feel about it after a few more months of e-biking...lol)
Your bike looks very nice BTW. :wink:

 

[MitchJi]

Judging by all the posts on broken hub motors, sensor problems, breaking spokes, torque restraint problems.... maybe they aren't so practical....

Hi,

Agreed.

I live at the top of a 1/4" mile grade that varies from 10% to 17% (measured). I want to be able to climb the hill with groceries etc. AND be able to cruise comfortably at 25 mph. I guess I could do that with a big CL but check the quality issues they have on ebikes.ca.

It seems to me that a motor driving through a geared hub or maybe a Nuvinci is the best solution. If I am going to do that it why not use the lightest, smallest and best quality motor I can get for the price? Using those criteria RC motors are a huge improvement over what is normally used on ebikes. The issue for me is should my first ebike be that far on the cutting edge which is what I am currently trying to decide.

 

[johnrobholmes]

RC motors only require more amps if they are making more power at a given voltage. Most are designed to work on lower voltage than a hub motor, so they will produce more power (in amp draw) as compared to a hub motor. Get one that is wound for 48 or 72 volts and the story changes. Ignoring efficiency, on 48 volts it would take the same amp draw to go 30mph no matter what the motor design. A watt is a watt, no matter what

 

[safe]

Brushless PM motors offers absolute speed control that is hard to duplicate on a series motor without adding extra circuitry and costly speed probes, sensors or tacho generators.

...this would NOT be a good controller since it needs hall sensors to work.

Are you sure?

This model seems to not need "sensors" of any kind, but I'm not an expert on this product at all.

Did you look into the specifics of this product?

They seem to claim that they do not need Hall Sensors. (at least that's what it appears they are saying :? )

However, it's very possible they built the controller so that it could run without sensors only on the mars brushless motor. (that might make sense)

 

[MitchJi]

Hi,

I just checked pricing on the Matex planetary reduction units:

From: James Van Hala
Subject: matex products
To: Mitch

Mitch,

Yes our gears can be coupled together with the use of a spacer between the units.
35S -$11.50 per unit.
75MAD or MLD $57.20 each
This is prototype pricing, we have volume discounts.

Regards
James Van Hala
Matex Products Inc.
216-228-9911

75MAD and MLD are here:
http://matexgears.thomasnet.com/viewitems/all-categories/lgu-75-m?&forward=1
This seems like a very doable solution. Two coupled Matex's would be 25:1. Pretty compact and light. About 1/2 pound, under an inch thick.

Some of them might even be strong enough (Max Torque - 300 lb-in.) for Matt.

This would require some kind of adaptor to couple the RC Motor to the input of the Matex and an adaptor to put a sprocket on the output. If it were done correctly this could also remove any load from belts or chains from the RC Motor bearings. It seems like it should be affordable to have the pieces machined to do this. Hopefully someone who knows will let us know how difficult (expensive) this would be.

 

[Miles]

Two coupled Matex's would be 25:1. Pretty compact and light. About 1/2 pound, .......

About 1 pound for two .....

 

[ZapPat]

Brushless PM motors offers absolute speed control that is hard to duplicate on a series motor without adding extra circuitry and costly speed probes, sensors or tacho generators.

...this would NOT be a good controller since it needs hall sensors to work.

Are you sure?

This model seems to not need "sensors" of any kind, but I'm not an expert on this product at all.

Did you look into the specifics of this product?

They seem to claim that they do not need Hall Sensors. (at least that's what it appears they are saying :? )

However, it's very possible they built the controller so that it could run without sensors only on the mars brushless motor. (that might make sense)

Re-read the page:

The Millipakâ„¢ PMAC controller operates in Trapezoidal or Sinusoidal waveform switching modes. Brushless PM motors offers absolute speed control that is hard to duplicate on a series motor without adding extra circuitry and costly speed probes, sensors or tacho generators. The Millipakâ„¢ PMAC brushless solution enhances system reliability and reduce warranty and maintenance costs.

Lots of ambiguity here, but I have one, and know it needs hall sensors. Proof (check for yourself):

View attachment SEVCON MillipaK BLDC motor controller MANUAL.pdf

This is the type of controller I have been working on for a while, but it will be MUCH more user friendly than this! And also not all potted up cause they're paranoid about people copying their design.
Also FYI, it is not intelligent at all at adapting to different motor types, which I guess reflects their lack of support when used on ither motors. It works OK on my ecycle motor as well as the mars, but tried to configure it with a comparatively small golden motors hub motor with limited success (higher no load current consumption and funny vibrations from hub motor).

 

[recumpence]

Wow, lots of activity on this thread today.

A few things need to be clarified here;

#1 The HV110 is nearly ideal for this, PERIOD! It is a fantastic controller. You do not even need to stay below its rated limit. You just need to make sure your wiring is short and large diameter. Also it is $269. Not too expensive.

#2 Any motor will pull alot of amps if geared tall enough and asked to accellerate hard. My motor is relatively efficient. It is not wasting power. In fact, it only runs luke warm. The reason it pulls so many amps is my riding style. I hammer this thing hard.

#3 I never built my bike to be practical and cheap. I built it to see how far the technology could be taken. That being said, I was expecting more problems than I have had. Pushing the limits causes parts to go. In fact, to a degree, I have been trying to break this thing. I want to know the weak links in the system. Well, there really aren't weak links at this point, per-se. What I have found is my inability to apply what I already knew to my electrical system. The ESC issue is my own fault for under guaging the power wire.

Bear in mind, this is still sort of an infant application of this technology. There are only a few of us doing this and, as far as I can tell, I am pushing the RC equipment harder than anyone else in the bike comunity. What that means is, I am going to hit barriers and have problems. That is a given. I could always limit my power to 4KW and not have any issues. But, I really want to know how far I can push this. Heck, I am out accellerating traffic (way out accellerating traffic) up to my 40 mph top speed. Also, it only takes well under 1kw to sustain that speed.

At any rate, I am not trying to say my bike is the best there is. Quite the contrary! This is such a new thing that I thoroughly expect my bike to be eclipsed by others in very short order. My bike is complicated and expensive. But, again, I was not after simplicity, but absolute performance and compact equipment.

What I am trying to say here is, do not discount RC equipment altogether just because I fried an ESC. Heck, that is like saying Kenny Bernstien's blown top fuel engine negates the use of internal combustion as a means of propulsion. Ok, not that my bike compares to Kenny's car, but you get the idea. :wink:

I have learned a HUUUUGE amount about this from my issues. I am far more confident with this setup now than I was before I started.

Anyway, we are all taking baby steps together.

Matt