Brushless motor for generator?

GoldenMotor.com

dracothered

New Member
Jul 25, 2012
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Howell, MI.
PM DC motor for generator (was Re: Brushless motor for generator?)

Have any of you used a brushless DC motor as a generator? I found one that I think will make a perfect one. It is here http://www.focalprice.com/YE310X/N3536_KV1700_40A_ESC_35mm_Brushless_Outrunner_Motor_for_Helicopters.html#.UOUmO6zJI09





Here are the specs:
Model: N3536 KV1700.
Diameter: 35mm/ 1.7 in.
Length: 36mm/ 2.0 in.
Constant Watts: 500W.
Burst Watts: 655W.
Product Net Weight: 128g.
Product Gross Weight: 228g.
Shaft Diameter (mm): 4mm.
Voltage Range: 11.1V-14.8V/ 3S-4S LiPo.
Sport: 1500g/ (0.87lbs).
3D: 900g/ (0.56lbs)
ESC: 40A Minimium.
Prop: 9.5″ × 5″, 8″ × 4″.
 

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BigBlue

Member
Nov 29, 2011
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California
Those brushless motors produce maximum power at very high RPMs and thus any electricity generated would require very high RPM engine or some fancy gearing. If you were to generate any electricity at the RPMs of the engines we use, it would not be very useful.

A front motor hub would be better because it generates electricity at a very low RPM. That is why people use them for wind power.

If you were to go this route, buy a gearless hub motor. Hub motors with gears have a uni-directional bearing that prevents any generation of power. It would just freewheel. There is a link on the Golden Motors forum from the owner explaining this.

I posted some information on the other forum with a link to a hub on Ebay, some videos that demonstrate the output capacity. See post #2.

http://www.motoredbikes.com/showthread.php?39715-Charging-Lighting-Systems

Another idea would be to use an induction fan motor with some rare earth magnets and a steel rotor. Green Power Science has a kit, but I think it's overpriced. You could find a fan motor at a garage sale or thrift store. I think Surplus Center has one for cheap. Buy your own magnets and cut your steel rotor from a wood pattern they show you how to make.

http://www.greenpowerscience.com/ALTERNATOR1.php

Be aware, if you watch the second video, it is very long and has too much fluff at the beginning, so I would recommend fast forwarding the video.

Good Luck,

Chris
AKA: BigBlue
 
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dracothered

New Member
Jul 25, 2012
973
1
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Howell, MI.
Those brushless motors produce maximum power at very high RPMs and thus any electricity generated would require very high RPM engine or some fancy gearing. If you were to generate any electricity at the RPMs of the engines we use, it would not be very useful.

A front motor hub would be better because it generates electricity at a very low RPM. That is why people use them for wind power.

If you were to go this route, buy a gearless hub motor. Hub motors with gears have a uni-directional bearing that prevents any generation of power. It would just freewheel. There is a link on the Golden Motors forum from the owner explaining this.

I posted some information on the other forum with a link to a hub on Ebay, some videos that demonstrate the output capacity. See post #2.

http://www.motoredbikes.com/showthread.php?39715-Charging-Lighting-Systems

Another idea would be to use an induction fan motor with some rare earth magnets and a steel rotor. Green Power Science has a kit, but I think it's overpriced. You could find a fan motor at a garage sale or thrift store. I think Surplus Center has one for cheap. Buy your own magnets and cut your steel rotor from a wood pattern they show you how to make.

http://www.greenpowerscience.com/ALTERNATOR1.php

Be aware, if you watch the second video, it is very long and has too much fluff at the beginning, so I would recommend fast forwarding the video.

Good Luck,

Chris
AKA: BigBlue
If you notice the top RPM of the motor I posted is 1700 RPM which is very doable right off the engines output shaft. Maybe I am misunderstanding something here about that RPM rating?
 

bigbutterbean

Active Member
Jan 31, 2011
2,417
3
38
Lebanon, PA
I would use it as a "bottle dynamo" type setup, running it off the rear tire with a rectifier and switching mode regulator. 14v would be perfect for charging a 12v battery.
 

BigBlue

Member
Nov 29, 2011
781
0
16
California
If you notice the top RPM of the motor I posted is 1700 RPM which is very doable right off the engines output shaft. Maybe I am misunderstanding something here about that RPM rating?
The one picture does state 1700 rpm per volt. So, if you are dealing with a 12 volt setup then it will reach maximum 500 watts @ 20,400 rpm (12 X 1700).

Theoretically, in order to generate 500 watts of electricity, it would have to spin pretty fast. Of course, your not going to be able to generate 500 watts, due to inefficiencies. In addition, lowering the rpms, say to 5000 rpms, isn't necessarily going to generate 12 volts or even 6 volts.

You want a system that starts generating at a lower rpm and within the rpm range of your engine. Alternators are probably best at doing this with a rectifier.

Here's a reference to get a more accurate rating of those RC motors:
http://www.rcgroups.com/forums/showthread.php?t=185271&highlight=bergmeyer

Good Luck,

Chris
AKA: BigBlue
 

Tool Maker

New Member
Oct 28, 2012
86
0
0
Las Vegas, NV
That is a polyphase motor. It will not perform very well as a generator.

That motor needs a 3 phase AC input from a switching controller to run.

If you want to build a generator you should use a DC motor with permanent magnets.

B.
 

dracothered

New Member
Jul 25, 2012
973
1
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Howell, MI.
That is a polyphase motor. It will not perform very well as a generator.

That motor needs a 3 phase AC input from a switching controller to run.

If you want to build a generator you should use a DC motor with permanent magnets.

B.
Why do they not make a good generator, please explain why this is so? Do these motors not have magnets in them?
 

Tool Maker

New Member
Oct 28, 2012
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Las Vegas, NV
Alternators in cars are indeed 3 phase. They also include a full wave bridge rectifier, a pair of brushes & a powerful electromagnet in the rotor. Automotive alternators require battery current to energize, and adjust charging voltage by changing the current in the rotor. Automotive alternators need 2 to 8 amps from the battery to function.

3 phase motors like that R/C motor may or may not have permanent magnets. They operate as induction motors do, from AC current. Generally motor manufacturers advertise magnets if they are present.

A polyphase motor with permanent magnets will generate electricity, but the voltage will be all over the place as the speed changes. You would need a 3 phase full wave rectifier, and the voltage would be uncontrolled.

Motors are never as good at generating electricity as they are at consuming it. Brush type PM motors have a fairly predictable output curve when used as generators. Check some sites where people are building wind generators from things like treadmill motors for ideas.

The Kubota alternator that is popular here is a single phase PM unit. The voltage regulator includes a rectifier, and simply turns excess voltage in to heat. They do work. Briggs & Stratton has used the same system for decades in bigger engines, that is why the B&S regulator works with the Kubota alternator.

A charging system for one of the chinese engines is a challenge, because the engine is only worth $80 ~$100, and nobody wants to pay much for such a system. For a 4 stroke with a way to drive a pulley the Kubota part works.

B.
 

dracothered

New Member
Jul 25, 2012
973
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Howell, MI.
Ok how about one like this?

28 Volt DC PM Motor


Used, LEESON model 46282512P1. Permanent magnet motor. Use for small blowers, pumps, etc.
SPECIFICATIONS

  • HP 1/25
  • Voltage 28 DC
  • Amps 1.8
  • RPM 4200
  • Reversible
  • Duty continuous
  • Mount face 1-1/4" sq.
  • Shaft 5/16" diam. x 1-1/2"
  • Size 2-3/8" diam. x 4-5/8"
  • Shpg. 3 lbs.

http://www.surpluscenter.com
 

BigBlue

Member
Nov 29, 2011
781
0
16
California
Go to this website to give you an idea how to find the proper permanent magnet motor to use as a generator even though it is a windpower site, the information is still relevant:
http://www.windynation.com/articles/wind/making-wind-power-how-choose-right-motor

By using the Volts-to-RPM formula, 28/4200 = .006666 as the Volts to RPM ratio. Multiply this by 2000 RPMs would give you 13.33 volts (.00666 X 2000). Then multiply 13.3 by .80 = 10.64 volts. At 2500 RPMs would give you 16.665 (.00666 X 2500). Then multiply 16.665 by .80 = 13.332 volts. At 3000 RPMs would give you 19.998 (.00666 X 3000). Then multiply 19.998 by .80 = 15.9984 volts.

So, in theory, you'd wouldn't be charging a 12 volt battery until you were at approximately 2500 RPMs with the motor you selected. It is a possibility that the efficiency rating might be 85%. In that case at 2200 RPMs would give you 14.652 Volts (2200 X .00666). Multiply 14.652 by .85 = 12.4542 volts.

These are only estimations.

Here's a new Kubota style alternator for $70.00 on Ebay. I offered $55.00 and they never responded. It is a great deal at $70.00, but I don't need it that bad:
http://www.ebay.com/itm/170921576775?ssPageName=STRK:MEBOFFX:IT&_trksid=p3984.m1432.l2649


Good Luck,

Chris
AKA: BigBlue
 

Tool Maker

New Member
Oct 28, 2012
86
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Las Vegas, NV
That 28v PM DC motor is more in the ballpark. A 50w motor, should be good for what you need on a bicycle. A DC motor generates DC power, so no need for a rectifier.

The next trick is using all of the power effectively. Spinning a motor as a generator, you can usually spin it about 15% faster than it's rated speed as a motor. So let's say a max speed of 4900.

Depending on the battery type & voltage, charge voltage can be adjusted by using a buck converter. Very little is lost that way, and charging near idle may be possible depending on the system.

B.
 

dracothered

New Member
Jul 25, 2012
973
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Howell, MI.
PM DC motor for generator (was Re: Brushless motor for generator?)

Ok I tested my PM DC motor that I just got.



At about 2500 to 2800 RPMs it puts out 16.5 volts with no load. This is about right because it works out to 1v DC per every 150 RPM (Rated: 28v, 4200 RPM).

When I put a 12v 35w(I think it is 35w) utility light on it the voltage drops to 15.3v DC drawing 2.5 amps. So I do believe with these reading it should work out great to keep a 12 battery fully charged all of the time. Let me know what you think.
 

oldtimer54

Member
May 15, 2010
540
6
18
On a bike
"Ok I tested my PM DC motor that I just got.



At about 2500 to 2800 RPMs it puts out 16.5 volts with no load. This is about right because it works out to 1v DC per every 150 RPM (Rated: 28v, 4200 RPM).

When I put a 12v 35w(I think it is 35w) utility light on it the voltage drops to 15.3v DC drawing 2.5 amps. So I do believe with these reading it should work out great to keep a 12 battery fully charged all of the time. Let me know what you think. "
__________________

Ive bought 2 of these and am wondering how your has worked out for you?
 

Citi-sporter

Active Member
Jun 16, 2014
206
43
28
North Bend, Or,
That is a polyphase motor. It will not perform very well as a generator.

That motor needs a 3 phase AC input from a switching controller to run.

If you want to build a generator you should use a DC motor with permanent magnets.

B.

You are mistaken, this motor would be fine for DC voltage with 3 bridge rectifiers across the adjacent lines out and the dc output combined off the rectifiers.

They are polyphase but not 60 cycle three phase, as they run off of a controller that feeds pulse width modulated and precisely timed AC square wave voltage, using the motor's permanent magnets RMF feedback as the brushless motor's sensor. These motor controllers are quite common in RC use and are known as sensorless controllers.

I fly electric RC planes. I've been using brushless sensorless controllers since 2003.

You will need to check the output voltage off of the 3 phases by chucking the motor shaft in a shop drill press turning 3100 rpm, and reading the AC volts out from each phase in turn to make sure they have got the same number of turns correct, or that there isn't an internal short or break in one of the phases.

It is not common in these hobby motors to have these faults, but it happens occasionally. The higher the working voltage of the motor the better the voltage output at a reduction in total amperage for size of motor.
 

bigoilbob

New Member
Dec 15, 2013
76
0
0
St. Louis, Missouri
Re: PM DC motor for generator (was Re: Brushless motor for generator?)

Have any of you used a brushless DC motor as a generator? I found one that I think will make a perfect one. It is here http://www.focalprice.com/YE310X/N3536_KV1700_40A_ESC_35mm_Brushless_Outrunner_Motor_for_Helicopters.html#.UOUmO6zJI09





Here are the specs:
Model: N3536 KV1700.
Diameter: 35mm/ 1.7 in.
Length: 36mm/ 2.0 in.
Constant Watts: 500W.
Burst Watts: 655W.
Product Net Weight: 128g.
Product Gross Weight: 228g.
Shaft Diameter (mm): 4mm.
Voltage Range: 11.1V-14.8V/ 3S-4S LiPo.
Sport: 1500g/ (0.87lbs).
3D: 900g/ (0.56lbs)
ESC: 40A Minimium.
Prop: 9.5″ × 5″, 8″ × 4″.
Too fast, too much power. Here is what I have used successfully for over 200 hours of riding for the last 3 years.

http://www.small-generator.com/Small-Alternator-YAF-54.htm

50-70 watts at 12-15 volts, at 2200-3200 r/m. Rectify with a $4 radio shack full wave bridge rectifier. Control the power with a little controller used for ~200 watt small wind turbines for (if I recall) about $30. Use a tiny, tiny, m'cycle battery for storage. The biggest logistical challenge is finding those tiny pulleys and the belt. But I did it, and if you are interested I will resurrect my manufacturers and their links. My power source is the intermediate shaft of a Staton tri hybrid gear box, and my prime mover is a Honda GX35. It all works GREAT together, and plenty of power left over (even after supplying 35-60 watts to my NuVinci shifter) for 12 volt front/rear lights.

Cautionary note. UR on the right track, brushless. Avoid using brushed motors as gens. The brushes get ate up right away. I spent $70-80 so you wouldn't have to....
 
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bigoilbob

New Member
Dec 15, 2013
76
0
0
St. Louis, Missouri
BikeE2 Tandem Recumbent/GX35/ NuVinci Auto Trans Electrical System

A couple of folks have asked for expansion on my BikeE2/GX35/NuVinci 171 Developer’s Kit (auto trans) tandem recumbent’s electrical system.
My system provides 0-70 watts of 12+ volt power, with over 45 watts available 80% of the time. I have used it for over 200 hours with NO electrical problems. It is homebuilt out of off the shelf components, none designed explicitly for bike use. But I believe the system is both “balanced” for m bike use and very durable.
I’m limited to 5 pics/post (veteran posters have probably found a work around), so I’ll probably have 2 posts.
My first pic is of the bike, with the engine stripped for centrifugal clutch inspection. The Staton tri hybrid gear box (more later) is visible behind the rear wheel. Also, please note the black box with the red handle, behind the rear seat. This is my e component box.
Second pic is of the permanent magnet, brushless alternator I chose, http://www.small-generator.com/Small-Alternator-YAF-54.htm. It is bolted down by 3 screws and the whole body (including integrated pulley) is of black nylon. I turn it thru the intermediate shaft of my tri hybrid gearbox, using this pulley, https://catalog.nordex.com/ca301, part #FZXC4005, and this belt,, https://catalog.nordex.com/ca301, part #FZX-A1-18. I obviously had to size my pulley and my belt length, but the pulley width, belt width, and belt material has worked out extremely well. I bought 2 belts, but after over 200 hours of use I have almost no belt wear or alternator “pulley” wear. Mounting the alternator took some thought, but the requirements are obvious. The pulley should be parallel with the power pulley (and remain that way in service), and a belt tensioner should be devised. Mine is not pretty, but it has worked well for me.
Here are my numbers;
Pulley pitch diameter ~2.9”
Alternator “pulley” pitch diameter ~1.75”
Honda GX35 “most used” r/m range – 5500-6000 (governed by auto trans). ~40% of the time. 1100-1200 r/m at the intermediate shaft. Alternator speed range ~ 1825-2000 r/m
Honda GX35 max r/m – 8000 ~40% of the time. 1600 r/m at the intermediate shaft. Alternator speed ~ 2650 r/m.
Honda GX 35 engine idle – 3000 r/m. ~20% of the time. Intermediate shaft not turning. Alternator also not turning.

Third pic is of my Radios Shack full wave bridge rectifier. No link here, as they are available from any RS. Just pay the few $ and get one with plenty of voltage, amperage, and (therefore) wattage capacity. Most of them do. Helpful hints. The ~ sign on 2 connections connotes sinusoidal ALTERNATING current and are your inputs. No wrong way to hook them to the alternator. You know what the + and – signs on the other 2 connections connote. They are outputs, and must match the signs on the controller inputs.
Fourth pic is of my Kintrex 100Watt Solar Controller, http://www.amazon.com/dp/B001HWQZNQ/ref. I just hooked up “loads” to my loads (my NuVinci microprocessor, shift actuator and front light), “battery” to my tiny lead acid motorcycle battery, and “solar panel” to the output of my full wave bridge rectifier. Amazon commenters have been able to heat it up with 80-100 watts of input, but mine is lower, and I have had no problems. This particular unit is also apparently out of stock, but a commenter touted this as a replacement, http://www.amazon.com/HQRP-Solar-Controller-Digital-Display/dp/B002GIWMJG/ref=cm_cr_dp_asin_lnk. Probably fine. IMO, I think these small solar controllers are ideal for MB charging systems. They are rugged, they turn down well since they must do that for solar systems, and they are designed to both send out conditioned power, and to charge a battery properly.
Fifth pic is of my 5 amp resettable circuit breaker. They are also available everywhere there are auto parts stores. I needed mine as a redundant backup to avoid frying my auto trans microprocessor. Since I thought my microprocessor might overdraw periodically, I wanted the auto reset. That has never happened, and I included this item just to remind you all that any delicate e loads need to be properly fused some kind of way.
More on next post.
 

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bigoilbob

New Member
Dec 15, 2013
76
0
0
St. Louis, Missouri
BikeE2 Tandem Recumbent/GX35/ NuVinci Auto Trans Electrical System

Sixth pic is my small motorcycle battery. I needed one because when I am decelerating my alternator is not turning, but I still need 12+ volts at 1-2 amps to run my auto shift microprocessor and to downshift. Mine was a discount brand. I used the simple lead acid, as it is more forgiving of charges/discharges and I require only 1-2 watt hours, delivered at 12-24 watts for a minute or 2, in between recharge cycles.
Seventh pic is of my front light. It is a Night Ryder 12 volt, 3 position light that had been powered by a rechargeable water bottle battery. When the battery failed I clipped it off and now power it from my controller.
Last pic is of my hub transmission, and motorized actuator, http://64.66.190.27/docs/DevKit_Manual.pdf. This is most of my “load”. Long story, but “sticky balls” are moved between input and output spheres, to enable a total transmission range of ~3.5. FYI, most CVT’s have a range of 2-2.5. These have gotten a bad rap because (1) they are really more suited for jackshaft apps with the power produced more from rotational velocity than from torque, and (2) they demand very well conditioned electric power. I have seen ZERO other successful MB apps, I believe for these very reasons. Folks hook them to tall wheels with powerful engines and/or don’t have stalwart charging/electrical systems. But my app is low powered (if low geared), my 20” powered wheel reduces the hub torque requirement. and I have no problem delivering 12+ volts to the actuator ( a Ford window motor with screw gear reduction) at 0-5 amps.
Happy to help with anyone’s specific calc requests, or any other questions.
 

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