Alternator to BLDC motor conversion

[Don P]

I had heard about this, found some old alternators in the Red Green pile, and was curious. I watched enough YouTube to think I understood it and ordered a cheapo controller. BLDC is "brushless DC" There is no commutator and brushes although with this setup I do have slip ring brushes. So its kind of hybrid I guess. A few sessions of playing with the wiring, and it fired up today. I had one battery hooked to it, I've seen 3 and was energizing the rotor with 6volts DC using about 4 amps through that charger and then through the slip rings. I had removed the diodes and am  directly wiring each of the 3 alternator phases directly to the controller. My hillbilly understanding is that I've charged the rotor with dc and made a non changing series of electromagnets around the circumference of the rotor. The controller is creating a swirl of magnetism in the coils of the stator. The knob on the controller adjusts the speed of the swirl, the switch changes the direction of the 3 phase swirl.


 



I had it clamped down to keep it from jumping around with the starting torque. No worries, there is no starting torque, I had to spin it up by hand. Once running it had some amount of power but at this point not enough to drag me up the mountain. I think the one in the 00's Yukon will be a 100 amp. I ran it for some minutes with no load, no apparent heat in anything I felt.

[Joe Hillmann]

What did you use for a controller?

I thought of doing the same but when I saw the cost of 1000 to 3500 watt controllers I gave up on the idea.

[Southside]

If you have to spin it by hand to start it does this mean you will need to cut holes in the floorboard on the Yukon so you can Freddie Flintstone start the vehicle?  :D

[Don P]

This was a cheapo $20 controller to play with the idea, I imagine I'll smoke it. Hall effect sensors should tell it where the rotor is in relation to the stator when it is stationary. With that type of controller I think there would be some amount of starting torque. I don't think this thing gives any feedback or it is picking it up by sensing the passing rotor field once it gets spinning. I tried 12v on the rotor and that seriously hindered it, so there is an optimum rotor field strength. I just had 6 or 12 volt choices with this setup. I could drill out the rotor and epoxy in some neodymium magnets to get rid of the rotor wiring. I guess then it would be a true BLDC.

It has not escaped my notice that any time someone shows, proposes or explains some alternative method or solution, the admins are the first to try to shut down the discussion. If this is not a desired forum, and that is fine, this is a forestry forum. Well, quit pretending that this is an area we are going to talk about and remove it. I'm good either way, I'm playing with it and willing to show what I know. It can be here or elsewhere. You control the medium.

[Southside]

Don - it was a joke based on what you said, I didn't say this wasn't a valid discussion, I actually tried to follow along with what you described and when you mentioned the Yukon dragging you up the hill, and having to spin start the current gadget, I pictured the old Flinstone mobile getting rolling.  Nothing more. 

[mudfarmer]

That's a hilarious call-out but you can't just blame the admins, this site is full of idealogues and I try not to read this and other sections of the forum and just stick to the straight forestry topics, occasionally failing like when Don posts an alternator conversion thread

[Don P]

I started this thread to create a build thread away from the other circus going on. I neglected to inform the clowns and took the head off the first one to not read my mind. Basically, when trying to develop something, a negative peanut gallery is counterproductive and creates a stifling environment. Notice what has happened to this entire topic, other than bickering, on a practical level its dead. Talk is cheap, I do stuff, so, stifle or get to work. I have anger management issues, deal with it  :D.

Meanwhile, 2 more batteries held a charge. With 3 in series, at 36 volts supplying the stator, through the controller, with 3 phase power and the charger providing the rotor with 6volts, it self starts and has a good bit more torque. Very good speed control forward and backwards, from crawling to WOT. Apparently my ammeter pooped the bed so I couldn't get a power reading.





I would say it is still fractional horsepower though. It took this much to stall it, and it could not self restart till I turned it off and on again. It wasn't trying, it was as if the controller was confused and shut down, it felt "off".


 

There is enough info to do some math and get into what Joe was talking about,
I didn't smoke the controller but I did get a whiff of ozone for a second at WOT and locking the rotor. It was probably right around the controllers 15 amp rating x 36 volts= 540 watts... 746 watts per HP
So it was cranking around 3/4 HP, that's believable. I think this controller can take 48 volts and the rotor voltage seems to have a marked effect on power.

The batteries could be a more compact lithium pack, the alternator the same. This is not a cart motor, maybe a bike. That would help with the low starting torque. All in all it works and it might be of some use on a deserted island, but it ain't much.

At $130 you can get into about triple the output with a controller and motor. This is one;
Amazon.com: BestEquip Brushless Motor Kit,2000W 48V 42A 4300RPM High Speed Electric Scooter Motor,with Mounting Bracket,Speed Controller Bicycle Motorcycle Mid Drive Motor : Sports & Outdoors

[Southside]

Clowns? Bickering? No, you chose to stomp your feet like a two year old because of a joke that I guess you didn't get. 

It's been said on here plenty of times, it's not the ideas, technology, etc that are the problem. It's the shoving it down the people's throat that is the issue.

Spent the whole day in Richmond dealing with some of these exact issues. 

If anyone wants to see it with their own eyes I can show you where our forest ground that has provided for generations of families is now providing for corporate interests in Germany, Australia, and just enough to  some in Boston to keep it US based. All due to mandatory policy being shoved down our throats. Now mind you, I don't agree with pine monoculture, not at all, but that's better than 4,000 acres of glass, job loss, and an exporting of our treasurer with every energy bill. I do plenty of things in very non traditional ways and hear the naysayers myself. 

[Don P]

That's pretty much what I was seeing walking in the door  :
This is a motor building thread.
Politics is on the 5th floor.

[Joe Hillmann]

Back on the topic of turning an alternator.

If you look up "Robert Murry Smith BLDC" on youtube he shows how to build a comunitator to speed controll large 3 phase motors at high watts using a very small and cheap motor and controller or even a cordless drill.

If there was a cheap way to get 3 to 5 hp put of them alternators would be awesome for DIY projects.  

[mudfarmer]

Veering slightly off topic, is a treadmill motor maybe something worth looking at if the goal is transport? They are permanent magnet, you can get them for free or extremely cheap, mine have all been 90v DC motors, they will run on whatever DC voltage you feed them and we know they can move a human on a belt, at least. Seems like they are 2-4hp. I have only used them in the exact opposite config as the alternators here -- spinning the motor to make a generator, rather than powering an alternator to make a motor.

[Wlmedley]

The first winter I spent in retirement I got a little bored and built a go cart.Something I dreamt about doing when I was a kid but didn't have the resources to pull it off.I got the frame built and welded up.Spent quite a bit of time and money getting steering geometry worked out.Bought,seat,wheels and tires ect.Then I quit on it and it is leaning against my work bench in the garage.Never bought an engine for it mainly because I couldn't decide what to put on it and if I did I would have to store I sort of level and it would take up more room which I don't have.This thread got me thinking maybe I could make it electric drive. I could store it standing up and not have to worry about gas going bad or oil leaking out plus if it was set up correctly could have plenty of power.My son and grandson would probably a good time on it.Having reverse was something I hadn't thought of but would be a nice plus.Anyone have any ideas.Would be pretty neat toy if I could pull it off.

[btulloh]

I bought another used electric golf cart recently, 2017 Ezgo, that has a lithium battery pack instead of the lead acid batteries that they used in the past. The battery pack only weighs 60 lbs instead of 600 plus pounds for a set of deep cycle lead acid batteries. The reduction in weight means much better performance in both acceleration and top speed and distance. You could take a motor, controller, and battery pack from one of these golf carts and put it in your go cart you'd have a screamin' fast machine. The whole power train could be easily transplanted into the go cart. Sounds like fun! 

[Don P]

I searched "golf cart motors" on Amazon and it was interesting seeing all the related parts as well as the motors. It looked like they were 2-5 hp. I saw several identical looking ones side by side, one had 40% more torque but a 14 mph top end, and another had low torque but a 25 mph top end. Might be worth looking for their schematics and see how that works. I saw a conversion to switch a golf cart over to electric, so the whole package, $2,000. Bare motors were ~$650 What are carts going for used?

The HP ratings I'm seeing, and obviously being used, seem low. Looking it up, I saw a post on woodweb saying electric is 2.5x the hp of gas, something about it being a constant torque difference.

I don't think that is the alternator motor. Just looking at the amount of windings in the alternator vs a strong motor, it just isn't there, and then it would take a large alternator and a correspondingly large controller. Speed for me is less important than torque with steep roads. The $130 one above is looking better.

[btulloh]

I paid $3800 for this one, as-is, coming back from a lease. Looking at cost of a motor, controller, throttle assembly, charger, and 56v lithium battery pack that's actually pretty cheap.  The battery pack is $2k by itself, compared to almost $1200 now for a set of deep cycle l/a batteries. The battery pack in the cart I bought still has 2 years left on the warranty.  

I'ii see if I can identify the motor and get the specs. Just guessing but it seems like it has more torque and hp than the ones you mentioned. They do make a range of motors for these things, but higher performance is gonna cost more. Could be something like a Cushman work cart might be a source of higher powered motors. I see used ragged out cushmans advertised for cheap though.

[btulloh]

https://www.extremekartz.com/motors-controllers/

[Don P]

@Southside 
Jim, I'm still trying to unpack my behavior. 
Safe to say I am failing to outrun the demons in my head, miserably, please accept my heartfelt apologies.

On topic, I looked at the 165 amp alternator in the dump truck, it has serious windings and tighter rotor to stator clearance. But, I'm also reading about this related to torque
Microsoft Word - GoldenMotor FOC Motor Controller Guide.doc

[Southside]

No worries Don, my sense of humor can be odd to get at times. 

How will the alternator get it's torque to the transmission? Do you have to use pulley reduction?  It is a very interesting concept.

[Old Greenhorn]

......, my sense of humor can be odd to get at times.
........

Ya THINK? :D :D :D :D :D :D ;D

[Don P]

Thanks for understanding guys. Best I can figure is if your busy beating yourself up and sleeping with one eye open. I can relate to Belben's neighbor stories. I've gone hair trigger. It'll pass.

I don't know enough to know anything about power transmission yet. The "motor" on the bench runs from ~500rpm to ~3000, where it seems to slip off the magnetic swirl and shuts down. I think hall effect sensors fix that and then the controller I linked above really dials in the stator to rotor phasing. ... for ~$750.

I followed that controller down a rabbit hole and have watched a couple of this guys videos. This one had some good tidbits after using one of their motor/controller setups for several years on his sailboat.

Ep141 Lessons learned after 4 years Electric Motor Q&A - YouTube

[mudfarmer]

Sorry Don for further derail but for what it is worth I would like to apologize as well.

I really appreciate this forum and the incredible amount of knowledge that the members past and present are willing to share. I owe you all a lot, hopefully enough said.

[Don P]

Well, I've splattered this thread  :D
Guys, It isn't y'all and I appreciate everyone's tolerance. I had an exchange with a neighbor that did not end well. My head has not been in a good place since, it isn't a daily occurrence for me. Best I can tell I just transferred anger, well that ain't good, this is supposed to be a diversion from the daily poo. Sounds like a good time for me to spend more time with inanimate objects.

I was curious at what point the smoke escapes the controller. No not that way  :D.  I looked up the MOSFET transistors that are doing the switching for the DC to 3 phase. They are rated to 100 volts, 180 amps and can dissipate 370 watts. There are 6 in the little controller I have, 3 pair of 2. I see the 5kw controllers have 18-24. The rest of the components and board I don't know about, the traces themselves are printed circuit so not much capacity. I've seen where some people have overlaid them with copper and solder to make for larger current carrying ability to those transistors that are producing the 3ph. I think the chips are timing, feedback, low current.

Part of the reason for hand starting this at low voltage is the lack of sensors to tell the controller where the stator and rotor are in N-S relation to one another. Just sitting there it cant figure out how to get the spin started. Once motion begins there is a feedback from the current draw to each phase as it passes the rotor's magnetism, and its off to the races. At higher voltage, when I switch on there is a twitch of the rotor, which is enough for it to sense. The better motors use a hall effect sensor, or a pair, to give it that knowledge. I think that would make it quieter too. The alternator has the sound of a 3 phase that is slightly out of phase, sort of like a rotary phase converter with an out of balance phase but not that bad.

All fine and good and probably worth exploring more. Dad built an electric bike he rides daily out of a couple of wrecked ones, but he doesn't know how it works other than plug and play. Looking at just buying off the shelf stuff this looked like it might work for a cart;
BLDC Motor Kit

I've looked quickly at treadmill motors and that is another way to go, brushed, old style which I think I understand better, I'm not sure what it takes to control them?

[Al_Smith]

Couple of things .A standard GM alternator is capable by passing the regulator will put out around 120 volts but my oh my do they get hot .Brushless DC motors are often called servo motors and are very efficient .Golf cart motors are series wound just like a starter motor that starts an automobile and controlled usually by the voltage through the fields .BTW I have two carts I bought for about junk prices .One an Ezgo I use 3 size 27 marine deep cycles hooked up in series to get 36 volts rather than 6 GC 10 or 11 six volts at $150 a pop and weigh 62 pounds each .The other one is a Cushman that came over on the Mayflower that uses a resister controller to regulate the field .That one is tarped down ,I don't like it .

[Al_Smith]

Now thinking out loud some thoughts .The drive motors for battery golf carts are very powerfull but they are also heavy and require some huge batterys .Mobilty scooters use smaller batteries and everything is lighter plus less expensive .Battery drills have been used for things like motorized bicycles with a certain amount of success .What all have in common is to find the exact type requires some action.To prove it you have to do it .

[mudfarmer]

Treadmill motor controll would be IIRC a PWM + pot, what you would need should already be on the treadmill in some form unless you want to get wild or spend money.