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Discussion Starter · #1 · (Edited)
Well since this last year has been a total shit show and I’m bored out of my mind. Have been in the middle of swapping a v8 into my s10. But I’m bizarre and despise being like everyone else so I thought why not an EV conversion?

Only issue, I know nothing about EV swaps.... but I’m a maintenance mechanic with a good basic understanding of electric and motor controls.

So I’m thinking of doing a DC forklift motor and keeping my s10’s manual transmission. So I found a 36/48v 18.4 KWh forklift motor. I can build an adapter plate, so I guess is this motor a reasonable rating?

I haven’t looked into batteries, but I’m thinking of using a 400 amp Curtis motor controller? Am I on the right track here?
122347


and said POS-10
 

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Hey, I am looking forward to seeing your build! You can check out my thread for lots of ideas of what not to do :). It sounds like that forklift motor should probably be fine - I gather that the ratings are very conservative, and people have put some serious power through them without too much trouble. If you have not at least skimmed the thread on forklift motors, I would say its worth a few hours of your time to go through it. You will probably need to advance the brushes to run a higher voltage, which I am sure some of the other members on here will have some info about. As for a 400 amp controller, it might be enough for a little run-about. I seem to recall those curtis controllers were fairly low voltage, and you might not be able to get much of a top speed with them. Hopefully someone else can chime in with some real-world info.
 

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You will probably need to advance the brushes to run a higher voltage, which I am sure some of the other members on here will have some info about.
My understanding is that brush advance is not directly for higher voltage, but rather for higher speed... and higher motor speed requires higher voltage.

As for a 400 amp controller, it might be enough for a little run-about. I seem to recall those curtis controllers were fairly low voltage, and you might not be able to get much of a top speed with them. Hopefully someone else can chime in with some real-world info.
The power rating is at the rated voltage (but in an EV you can run much higher voltage for higher speed) and for continuous or perhaps one-hour duty (but in an EV you can push much more current, producing more heat, for the short time you need it for a burst of acceleration).

18.4 kW of mechanical power output would correspond to more than 383 amps at 48 volts (how much more depending on efficiency) of electrical power input. That suggests that 400 amps is likely just enough to meet the peak current demand to match the rated performance, and enough for the same torque but more power by running at higher speed.

Curtis offers controllers in various voltage ratings, starting down in the rated range of this motor and going up to about three times as high - still low by modern EV standards.

Triple the original 48 volts at up to 400 amps might provide a peak output power (only in a narrow speed range) of roughly 50 kW (67 hp). If you can shift to keep the motor in the speed range it needs that's enough to drive around, but less than any stock S-10.
 

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Discussion Starter · #4 ·
Interesting, I’m not looking at building a world eater. Just a daily that can do at least 45 mph and have about a 60 mile range. I drive about 15 miles to work one way. I actually have a 48v charger that I got from a scrapped business so I was trying to do this as a 48v system.
 

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I actually have a 48v charger that I got from a scrapped business so I was trying to do this as a 48v system.
At only 48 volts performance will be very limited. 18.4 kilowatts is 25 horsepower; it's questionable whether it could even get to 45 miles per hour.
 

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Discussion Starter · #6 ·
Well that’s slightly disappointing, so I should be looking into potentially a 96v battery bank and a higher voltage motor controller to match.

Will it be an issue to run 96v on a 48v rated motor? Unfortunately as a maintenance mechanic I don’t know much about using motors outside of their designed purpose.

I guess I figured being a motor from a 6,000 lb forklift it would certainly have the umph to push my 2600 lb truck around and having a manual trans would allow for higher speeds. EVs are quite the different beast it seems coming from a caveman fire powered auto perspective
 

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Will it be an issue to run 96v on a 48v rated motor?
No, this has been done plenty of times (but not by me). I would suggest taking a look at Duncan's Dubious Device for what sort of punishment forklift motors can handle. Duncan might be able to chime in with some details - I cant remember off-hand what he did about advancing brushes, or what voltage his motor was originally rated for.
I guess I figured being a motor from a 6,000 lb forklift it would certainly have the umph to push my 2600 lb truck around and having a manual trans would allow for higher speeds.
Yeah, the motor has plenty of power to move a truck, the problem is the motor speed. I have not really taken the time to completely understand how DC motors work, but I think it is basically as follows: As the rotational speed of the motor increases, so does the back EMF (the voltage being induced in the windings from moving through a magnetic field). Which just means that to accelerate you need to raise the input voltage beyond the voltage being generated in the motor. Acceleration obviously causes even more back EMF, so basically for a given voltage there arises a maximum RPM, beyond which the motor cannot spin any faster. You see this when using a 12v source to test the motor. It will spin up to a certain speed, and then stay there. 12v is used because it keeps the motor speed down when it is unloaded.

So basically lower voltages inherently limit you to certain motor speeds (dont ask me how you would compute what those are, I have no idea). But this makes sense on a forklift- the motor does not need to spin fast - it just needs to generate lots of torque to move a huge weight around.

Really, I think for a DC build it maybe makes the most sense to start with the controller and work backwards from there. Any reasonably sized motor (around 150-200lbs 9-11" diameter) should work. Then you design your battery to deliver the max input voltage for your controller.
 

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Will it be an issue to run 96v on a 48v rated motor? Unfortunately as a maintenance mechanic I don’t know much about using motors outside of their designed purpose.
No, this has been done plenty of times (but not by me). I would suggest taking a look at Duncan's Dubious Device for what sort of punishment forklift motors can handle.
Typical motor ratings are for continuous, or at least an hour at a time, operation. As this example shows, they can be pushed much harder... briefly. Duncan runs competition events in which full power is used for a few seconds at a time, at most. If you push them hard for a sustained period, they overheat and eventually fail.
 

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I guess I figured being a motor from a 6,000 lb forklift it would certainly have the umph to push my 2600 lb truck around and having a manual trans would allow for higher speeds. EVs are quite the different beast it seems coming from a caveman fire powered auto perspective
The limitation is power. You can move a freight train with one horsepower, if you are willing to do it slowly enough, by just gearing down the motor output. This is no different from moving things with engines. A 400 horsepower engine can provide extremely high performance to a one-ton sports car, lots of performance to a 4-ton pickup truck, functional performance to a 20-ton highway truck, or effective movement for an airport tug moving a 70-ton airliner.
 

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The limitation is power.
Well, it seems to me that I am maybe getting into the weeds, but the limitation on power is as you pointed out above all about heat. The motor is rated for a certain power for a certain time by the manufacturer - in this case 18kw for (probably) and hour. But the motor is not physically constrained to producing 18kw.

By increasing the voltage the OP should be able to get short bursts of much higher power - and with the addition of more cooling could probably drive at a higher power level for relatively long stretches. My power estimates suggest that an S-10 should be able to go 50mph on flat ground on about 15kw. Acceleration will take more, as well as going up hills. But as long as you are not driving over the mountains, the forklift motor should probably be fine. You just need enough voltage to make it go the speed you want, and a way to remove the heat if that speed takes much more than 18kw to maintain.
 

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Discussion Starter · #11 · (Edited)
A lot of interesting stuff here, thanks for all the replies. Definitely a lot to digest. Think after discussing all this I might look into a slightly smaller motor with a higher rpm range.

Plus I might look into an 8” motor, found out CAN-EV has a discounted s10 adapter plate with flywheel spacer on sale for $280 right now.

So are there any specific DC-DC motor controllers that anyone has experience with that they recommend?

Also the Ac-50/51 series, I’ve seen kits for $3800 or so for motor and controller plus they’re setup for regenerative braking. Does anyone here have any experience with these? Seems like a nice setup but I feel like it’s just an AC forklift motor and Curtis controller, which I could source used cheaper than that. Or is there something theAC-50/51 has that sets it apart from an AC forklift motor?
 

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Also the Ac-50/51 series...
Does anyone here have any experience with these? Seems like a nice setup but I feel like it’s just an AC forklift motor and Curtis controller, which I could source used cheaper than that. Or is there something theAC-50/51 has that sets it apart from an AC forklift motor?
It should be pretty similar, but I have heard (in this forum) that HPEVS buys standard industrial motor parts and has them wound for the desired voltage range, rather than using AC forklift motors.
 

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Discussion Starter · #13 ·
It should be pretty similar, but I have heard (in this forum) that HPEVS buys standard industrial motor parts and has them wound for the desired voltage range, rather than using AC forklift motors.
Hmmmm wonder if I could find said specs, I work for a wire and cable manufacture and see boat loads of mag wire go through here. Can’t be too hard to rewind a motor I imagine. If not I could at least get the wire at cost and ask our local motor shop to do it.

With AC motor controls being so common now is it worth just skipping a DC swap?
 

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I think there is still a time and a place for an old-school DC setup, but they really should not be the default choice anymore. DC I think is in its element for a cheap and simple drag racer setup where efficiency and regen are not important. For the electrically savvy, they can be a very cheap way to go if you build your own controller. There are still used DC controllers floating around for a good price, but buying them new is getting harder, and frankly not very cost effective anymore.

There are off-the-shelf AC options, which is what I went with just because I wanted something that was easy. If you are more constrained by budget, then you can get all the advantages of AC by reusing a motor out of something like a leaf. I see complete, still running leafs on craigslist for less than $3500 all the time. The batteries are probably terrible, but at that price, it would be worth it just for the motor. Consider the batteries as just a stop-gap solution to get you up and running. If I had WAY more free time, I would have bought and gutted a leaf.
 

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Discussion Starter · #15 ·
That’s actually not a bad idea, didn’t realize leaf motors are so cheap. $700 or so for a 2012 motor isn’t bad. I guess the question would be do I adapt the motor to my existing manual trans or what do I use for a transmission? Looks like leafs use a single speed transmission since the motor has an operating range of 10k rpms.

Also talked to my coworker about making one of these 200kW AC motor controllers, he builds computer boards in his spare time.

 

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Looks like leafs use a single speed transmission since the motor has an operating range of 10k rpms.
Yes, like essentially every modern EV. The reduction ratio in this case is about 8:1.

Also talked to my coworker about making one of these 200kW AC motor controllers, he builds computer boards in his spare time...
The most common approach for controlling Leaf motors now seems to be to use the original Leaf inverter, and either replace the controller logic board, or to use an additional controller to provide all of the CAN communications that the stock controller needs to operate outside of the normal environment of a Leaf. But building a controller/inverter would work, too, if you configure it with the right parameters.
 

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I cant recall the details of the drivetrain, but the user Tremelune used a leaf motor in a recent (and well documented) build. Now that I think about it, I seem to recall him getting an adapter plate made, so he might have kept his transmission? Might be worth a look:


I think he used an after-market control board that makes use of the leaf inverter. I think its a 500$ part, but it makes wiring it all together easy enough for anyone to do. Having a custom controller made sounds like a serious endeavor to me, but with the right tools and knowledge, anything is possible. Really it all boils down to what you think sounds the most fun. Either way, document your build! Its always fun to see what other people are up to.
 

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I cant recall the details of the drivetrain, but the user Tremelune used a leaf motor in a recent (and well documented) build. Now that I think about it, I seem to recall him getting an adapter plate made, so he might have kept his transmission? Might be worth a look:


I think he used an after-market control board that makes use of the leaf inverter. I think its a 500$ part, but it makes wiring it all together easy enough for anyone to do. Having a custom controller made sounds like a serious endeavor to me, but with the right tools and knowledge, anything is possible. Really it all boils down to what you think sounds the most fun. Either way, document your build! Its always fun to see what other people are up to.
The control board is pretty cool, but if you have programming skills and some hardware skills, you can put together a raspberry Pi with can controller for around 60$ and control the stock Leaf inverter. The biggest challenge with the Leaf motor/inverter combination is interfacing to a transmission. You can now buy a piece from 'bratitude' here on the forum of you can have one made if splines are your thing.. I'm using a Pi and my own coupler in my Electrified Miata project, found at bbitnerblogs.com/e-miata


Bill
 

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Discussion Starter · #20 ·
Interesting Idea, I was discussing this with my coworker who is our IT guy. He has experience using the raspberry Pi units, thinks it shouldn’t be too hard.

As for motor to transmission I have steel plate I’m going to measure and see if I can make a temporary slip on coupler and line up the leaf motor with my t5 transmission. Then make an adapter out of said plate. Looking at gear ratios if I use 3rd gear only coupled with my rear axle ratio I’d be looking at about 7.8 : 1 ratio. So it would be basically useless other than a convenient way of having a reverse gear to shift to.

I did see somewhere on here though that someone made a leaf motor to common 8” motor adapter. Which I could then bolt to a CAN-EV adapter for my t5 trans. But adapter plate on adapter plate seems excessively redundant, and then need a new flywheel spacer.
 
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