# "Overclocking" a lower voltage motor...



## ArJay (Dec 14, 2007)

Sifting thru some past threads and came across a post which talked about running lower volt forklift motors at a higher voltage...



TexomaEV said:


> I see others out there using 36-48volt forklift motors @ 120+vdc, one gentleman mentioned in a email, he'd been using one now for over 10years this way.


http://www.diyelectriccar.com/forums/showthread.php?t=1908

Can anyone extrapolate on this? Can it be done (reliably)?

R


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## houseoffubar (Nov 18, 2007)

For the most part, you are limited by temperature. The more you "overclock it" the less time it can withstand that voltage without overheating. Some motors have advanced cooling to help the motor take the heat. 
Basically for acceleration you will probably be OK, but if you are pulling a lot of amps going up a mountain pass, you will have trouble. I have also heard of people having their motors reworked, to up their voltage capacity, but I really have no info on this, and suspect it isn't cheap.
I'm sure someone else will have much more informed thoughts on this subject, Stay tuned, Eric


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## ArJay (Dec 14, 2007)

Thanks Eric...

The other post mentioned that you'd draw big amps doing this. Is that where the heat would become a factor? Would that mean that range would suffer too?

Have to do a bit more research on the subject I guess. As you know, I'm pretty green when it comes to electronics...

Also thinking it might be a bit difficult to insure if the insurer found out you were pumping twice the rated voltage thru the motor....

Rory


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## mattW (Sep 14, 2007)

For any set power level (i.e. a cruising speed) the amps in a higher voltage motor will be less because the total power = voltage x amps. higher voltage means less amps for the same power level. I'm pretty sure the problems with higher volts is to do with the new capabilities of the motor. Higher volts means more power for acceleration and hill climbs which also means more heat in the motor and batteries. To quote Austin Powers "Its not the size that matters, its how you use it..."


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## ArJay (Dec 14, 2007)

Ah ok thanks Matt.
So from what I can gather it's the amps that create the heat as a result of the increased voltage thru the motor (especially during times of intense load)?

What actually transpires when a motor overheats? What's in danger of failing?

R


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## ArJay (Dec 14, 2007)

FYI (you may have already seen it ) I've been looking at Jack Knopf's setup on his Chevelle...

http://www.poormansev.com/id22.html

Looks to be running a 36V GE forklift engine rewired to take 3000 plus amps. 

Interesting...


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## Hi Torque Electric (Dec 23, 2007)

In general, the only real difference is the wire size and amount of winding turns between let's say a 36 volt (AKA forklift motor) and something rated higher (like the Warp / ADC motors. In fact I've modified a number of lift motors being used as drive motors for EV's, both cars and MC's. Advancing the brushes (to align with the warped over field magnets which keeps the brushes from arcing) and dealing with the existing shaft are the two biggest issues if looking at using a forklift motor. With that said, there are better choices than others, with some being great while others are not. I've been viewing peoples motor choices on the EVDL for a couple of years now and will offer it here to send me a pic's and I'll offer advise as to how I think it might do for you (before you buy) if so desired 8^)

Using a courser wound motor will cost you more amps but will have a higher top end speed at X voltage. As an FYI, current equals torque and voltage equals RPM's. Another piece to obtaining a good motor choice really comes down to the mass of the copper and steel. You could wind a slot car motor to take 200 volts but it still wouldn't drive your conversion. In general the smaller the motor (and or the higher the current) the shorter it's duty cycle will be at a given load. A modified 7" Prestolite and an ADC FB1 9" motor can both be used for a conversion but the 7" motor will probably need to be blower cooled in anything but a light convertion. 

Hope this helps.

Jim Husted
Hi-Torque Electric


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## mattW (Sep 14, 2007)

Yay just what i wanted for Christmas! Someone to answer our motor questions! Welcome to the forums Hi Torque.


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## ArJay (Dec 14, 2007)

Thanks heaps Jim...awesome reply! Learn't a lot from that post....

A few more questions if that's ok...

In Jack Knopf's setup he's actually had the motor rewound to take a higher amperage? 

When you say "dealing with the existing shaft" are you talking about the actual coupling with the trans?

In your opinion is it worth the buggering around/cost of sourcing a suitable forklift motor vs a new EV item?

Thanks again for your time mate.
Rory


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## Hi Torque Electric (Dec 23, 2007)

Having read back through this thread I wanted to start with a couple of things. Current is what causes heat, heat can / will wear out your insulation. Picture putting a piece of cardboard in your oven and cranking it to 500 degrees. It'll take it for a little while, but as time goes by it'll get hot enough to catch fire. Just a little visual for you as it's basically the same thing for a motors insulation. By turning the oven down to 425 it'll prevent it from catching fire but as with the cardboard if left at a high temp for long periods of time the insulation becomes weakened. Keeping the motor cooler will increase it's life span. The other issue with heat is it makes things softer and you run a higher danger of blowing the commutator apart at the high RPM's.

As for rewinding a motor, sure it can be done (fields easier than armatures) but it'd be to allow a higher voltage and not current which was stated but it gets spendy so at this point a new motor starts to even the field. 

Any decent sized motor will take a full punch from a Zilla (at it's voltage rating let's say) but it's how many volts will it take before it can't commutate the voltage switching from comm bar to comm bar. As for advancement of the brushes, they commutate in line with the field magnetics. If that magnetic pole has been pushed away by the armature acting upon it, then the brushes are no longer in their "sweet area" and they arc.

As for using forklift motors at a higher than rated voltage, you need to understand that it's just one reference point. I've see (and built) a number of 7" 36 / 48 volt Prestolite motors for 120+ volts and they run just fine (as long as the conversion is light or they're blower cooled). At just 70 to 80 lbs though they are as small a motor as I'd advise using. Getting a hold of a 9" or 11 " 150 lbs to 200 lbs forklift motor would rock your boat so to speak (if you can feed it, lol). 

Here's some pro's and con's to using a lift motor (which I have moded a number of for people) as I see it:

Pro's:
The biggest and about the only reason to go this route is getting a cheap or free core by seaching scrap yards and Ebay sales, where If found local it saves you additional money in freight savings. Another reason is some like the good old fashioned, hands on, DIY way of doing things and having walked a few through it, is one reason I started my site (although as a one man shop it's hard to take pics of myself actually doing anything lmao). 

Con's:
The Warp / ADC style of motors have adaptor plates and blogs of how to do it from other before you. Using a lift motor forces you to pave a new road so to speak. Buying a taper lock is much easier than trying to match up some funky forklift spline as another "issue". I have found keyed shafts for the 7" through 9" ADC/Prestoliet/Crown motors that I can remove and replace with but many would need a cutom shaft to be made. Sometime you get lucly and the shafts thick enough to be turned down and have a key machined. If you could have a piece broached to mate you'd be golden as well. 

You'll also need to advance the brushes (usually done by rotating the CE plate 10 degrees in the opposite direction of intended rotation) where you mark/ drill / tap new mounting holes. Unless you've found a new or super clean motor (which does happen) plan on changing the bearings and turning the comm (even if you have to sub this part out to a shop) while you're in there anyway and try to factor in some clean up costs. 

There is no way I can describe to you how and what to look for here but in general look for golden or wine colored insulation, brush leads that are copper in color that haven't been cooked (a motor with good reusable brushes is a perk). Also try not to look eager to buy as the price goes up lol. If someone isn't willing to bargin down to your budget leave and come back in a week or two and check again 8^) I have cores that are based on their "usefulness" that fetch a better price but I usually pay more for them as well. Look for comm's with a lot of bars, if you look in ( a window) and only see a few and they are 3/8th" wide, pass on that one and look for a better choice (more bars more voltage). 

One piece of advise here, take your time and get a nice choice. Alomost 1/2 the motors I've built are still sitting undriven, so unless you have controller and batts in hand you probably don't need a motor asap.

As another FYI as I'm thinking of it 150 volts at 100 amps is the same as 100 volts at 150 amps. The reason most people go with the higher voltage route is it allows you to use smaller cable, ect, plus it costs you less current for a given HP. 

For those with the ability there really are diamonds in the rough to be found out there! There are a number of lift motors that are all but the same motor as the popular ones with the shaft and DE plate being the difference.
Guess that's about it for now
Jim


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## ArJay (Dec 14, 2007)

WOW....awesome post yet again Jim. Kudos++++ This should be a "sticky"...

I'm personally I'm looking at converting a small hatchback for commuting to work etc. 
The 7" 36/48V motors you were speaking of...would it be better to get a professional such as yourself to set a motor up for the intended purpose, or is it something someone with limited know how can diy?

Thanks again mate for all your help and info.
Rory


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## Hi Torque Electric (Dec 23, 2007)

First, thanks for the kind words.

It really depends on ones skills, budget, and value set on ones time. Last year Damon Henry (an EVDL member) who lives in Vancouver WA came down with his 16 year old son for spring break for a little motor schooling 101. I helped them locate and buy a core which Damons son Mike reworked in two days. He did have my shop as a play ground and my brain as a guide but he did most if not all the work himself.

The motor was installed into a Datson truck and is to be Mikes first car and to be used to get him to school and back. Anyway I was pleased to have been a part of a great father and son project, although it caused me to become a little behind as I had played for two days lol.

Anyway if a 16 year old boy can do it I'm betting that you could do it as well, of course having the tools and toys to play with make the job a little easier. About the only major issue you'd have is the armature. If you find that the motors shaft just isn't suited than the cost of shipping just it up is small tators, and I could reshaft it and turn it and send it back where you'd just have to put it all back together. Again in as much fun as this might be to one, it'd be a nightmare for others and is why sometimes I get whole motors while others send in just parts for me to work over 8^)


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## ArJay (Dec 14, 2007)

Cheers Jim...

I was looking at this blog last night. Shows a little bit about rebuilding a gungy old lift motor...think he mentions your name in there as supplying the brushes.

http://www.electric-lemon.com/?q=node&page=4

Are there any resources you can recommend (websites, books, etc...)?

When you talk about reshafting the armature what's involved? Is there anything to look out for when selecting the motor in the first place to make it easier/avoid having to do this?

Thanks again, learning at a great rate...
Rory


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## Hi Torque Electric (Dec 23, 2007)

Hey Arjay

EVen though I've built motors since 1981 I've only been mod'ing them for EV use for the last couple. There are so many motor types out there that have been used in forklifts that there is just no way I can word what I know into something you'd be able to relate to without some form of refferance. This is why I do offer sending me pics which I could offer my two cents on before one were to buy, not the best way but beats buying blind, lol.

I did supply the bruahes for that GE motor, whiched turned out was very dirty and actually had been overheated pretty good. That's actually (for me anyway) one reason I offer a look for people so that they do buy a clean viable motor.

Pressing the shafts from these armatures isn't rocket science but you can crush the comms if you aren't setup and know what you're doing. I still have to bore some of them out as I know I'll crush the comm down if I didn't stop pressing (actually I still crush one EVery once and a while)(these arm shafts are designed to "not" be pressable).

The Gamera 9 (Gamera's the monster that fought God(Zilla)(linked from my site) that started life as a 72 volt 9" Prestolite (model number MNF) that I reshafted and swapped the drive plate to the standard FB1 style. The best that I can offer is to look through the pics at my site and study what the comm bars and windings look like. As you look at core options you'll notice things that look the same. I'm usually close to my computer and try to get back to people quickly if there is a need for quick info (10 minutes till Ebay auction end, you know that kind of thing, lol). I'll try and get some unpublished lift motor pics at my site as a guide when I get some free time, how's that sound?


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## ArJay (Dec 14, 2007)

Sounds great Jim. I've been picking my way thru your site...it's brilliant. You sure do some quality work.

Thanks again for taking time out to answer the newbie questions. Hope you don't mind if I shoot a few more your way when I've found something worthy...

Rory


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## MARTY (Dec 16, 2007)

Hi Jim;
Would you answer a question that I have.... What is the difference between the different Motors Advantages and disadvantages... I have a D&D Motor, which I like and am happy with.. I have it in my Bug, a 144 Volt Series Motor, which I will run at 96 volts. All else being equal.  I hear alot about Warp and Advanced Motors, So not only for my future information, but I am sure others would like to know.. Are they pretty much the same or what ???
THANK YOU Marty


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## Hi Torque Electric (Dec 23, 2007)

Advance was formed by some old Prestolite EE's, and D&D was an offshoot from ADC who went off and started making thier own brand (although just 6.7" and under). NetGain jumped into the game with their versions and then started making larger motors than what ADC has to offer. In general, thay are all a good motor and there are things that I like and don't like about individual motors per se but get's a little tough to describe it all in a short posting. Sometimes it comes down to attention to detail (like the issues I've found and fixed on just about all makes. 

With that said, I'm promoting the Netgain motors as it seems they are very pro-EV and are very open to suggestions and input of things I've found. With that said I try to support those who are doing what they can to improve EV tech! All and all they are very much so very closely comparable to each other and are in general very reliable motors.


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## MARTY (Dec 16, 2007)

Hi Jim;
THANK YOU for your prompt Reply !!!!!
Would you agree that 96 Volts is about right for a Bug, Given the weight of the Batteries.... About 85-90 pounds each, I would Guess. With the Curtis Controller I have , I can go up to 120 vols...Right now I have 8 12 Volt Batteries, I got these used... They seems to work fine... or for more Range could I use 12 8volt batteries, when I can raise the money ???? 
THANK YOU Marty


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## Hi Torque Electric (Dec 23, 2007)

Hey Marty

Your question doesn't give me enough info to go on, and then, EVen at that is kind of subject to individual wants or needs. Face it what John Wayland might term "about right" as a voltage, might also be a little more than you'd need 8^o

If we look at the general rule of voltage= speed, and amps=torque, 96 volts might give you more than enough top end speed, if you're a "driving miss daisey" kind of guy 8^) or it might not EVen float your bubble if you're the "gone in sixty seconds" type 8^o I built a 7" Prestolite (fairly close to your motor size maybe a bit bigger) a while back that was put into an older super light Honda, that I heard did 55MPH on 48 volts (although I've not seen it, as it's out of state and haven't confirmed, but was from a reliable source). Marko's Fiamp using a 7" Presto does 90 MPH under 120 volts as another example.

I have no idea what motor you have (I saw 144 volts on the one posting) but if they've set it up to run 144 volts (finer wire and more wraps, and advanced the brushes to boot) then it may have issues running on just 96. Feel free to send or post pic so I can put an eye ball on it *^) Try and get the pole shoe bolts "and" the brushes in the same pic so I can see how advanced the brushes are. Advancing the brushes get's you a higher RPM @ X voltage, and allows the motor to run at a higher voltage (without flashing over) but you loose torque the farther from neutral it is. With that said at just 96 volts you may need to, or want to move them back toward neutral a bit (not directly neutral mind you). You'd probably need to drill and tap holes in between the two you have now. Again I'd know more after pics.

As to the 12 vs 8 volt batt's, sorry I'm just the motor dork here 8^o so I'm learning that aspect of things just like EVerybody else 8^) and hopefully someone more versed on that side of things can answer that part better than I can. I will say that in general, I think it'll be just fine, but like I stated there just isn't enough info to make an edumacated guess with the info on hand.
Hope this helps
Cya
Jim


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## MARTY (Dec 16, 2007)

Hi Jim;
Thank You for your prompt reply !!!!!!
What I have is a D&D Motor Model Es-31B which is 6.7 in. X 15.5 in Lng. It is Rated at 90 hp @ 144 Volts DC. At he Present I have it at 96 Volts.. With a Curtis Controller (I think) 1221 B , Maybe C.. 72 volts to 120 Volts at 400 Amps... It is in a 1971 Bug... I just wrote you another email about 96 volts Vs. 120 volts and whether the car would support the added weight ???? And if the Motor would be less prone to overheat with the 120 volt versus 96 volt option.... 
THANK YOU Marty


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## MARTY (Dec 16, 2007)

Hi Jim;
I forgot, The Motor is basically brand New, Built 12 - 19 - 2007, I got it on the 29th, and it has been run at the most 15 to 20 minutes...   Unfortunately, right now I am in one state and the car is in another state....   
THANK YOU Marty


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## Hi Torque Electric (Dec 23, 2007)

Hey Marty

A general rule (or so I've been taught) is volts up amps down. Running 120 volts at 100 amps is the same power as 100 volts at 120 amps and 125 amps at 96 volts. This is just an example and doeasn't account for battery sag ect. If the motor is rated to 144 voltas then running it between 120 and 144 will get you it's best eff. Now, that's a long 6.7 but it's not a 150 lb 9" so the more weight you add to this convertion the harder the motor's going to have to work. Keeping the motor RPM's up, say, 3K to 5K will keep the motor in it's sweet spot and where the motor RPM's allow the internal fan to push air. If the motors turning slow (and grunting hard current) (AKA hills) it isn't getting any air cooling.

As to how the weight will effect the conversion, I'm just the motor guy and would have little input other than Marko stuffed 10 12 volts in a Fiat 600. Have a look at the EV photo album (linked from my site)(easy google)to see what others have done with bugs. Not sure if you've been there or not but you can search by vehicle type and then click VW, there's got to be a number of Bug conversions there.
Hope this helps
Cya
Jim


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## SirisC (Feb 8, 2008)

At what point is a higher voltage a hindrance instead of a benefit? I know that a high enough voltage will ionize air and spark across it, but that takes ~30kV per cm distance between two points. So what keeps someone from building a 10kV/10 Amp system instead of a 200V/1000 Amp system?


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## Dennis (Feb 25, 2008)

> At what point is a higher voltage a hindrance instead of a benefit? I know that a high enough voltage will ionize air and spark across it, but that takes ~30kV per cm distance between two points. So what keeps someone from building a 10kV/10 Amp system instead of a 200V/1000 Amp system?



For DC motors there is a limit due to the fact that they require commutation via the use of brushes and commutator to switch the polarity of the current in the armature conductors. The down side is at high voltages there is a high chance of flash over in where there are arcs jumping commutator bar to commutator bar until the arc reaches the other brush, causing a dead short since an arc IS a short circuit although there is no physical connection (plasma is a good conductor!!!). Obviously this can be mitigated by brush timing advancement and/or the use of interpoles. Still there is a limit to such that even these techniques will not help. The highest voltage I heard about is 750 volts for large DC motors used in locomotives and some higher 1000+ volt motors used in paper mills and steel mills.


For asynchronous AC motors the voltage rating can be much higher as there is no commutator or brushes needed because the rotor receives its current from electromagnetic induction (think of a transformer). These motors can be rated to about 15Kv. Its not too hard to tell if its high voltage because they will be covered in glyptal--a red colored paint that is a good electrical insulator. However, there is a limit as well for these motors, as the insulation material such as the glyptal and varnish on the windings will breakdown at very high voltages resulting in corona. The corona will eventual damage the insulation to the point of exposed copper and then an arc will occur, leading to catastrophic failure (the phase windings of the stator will be charcoal black).


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## Bugzuki (Jan 15, 2008)

MARTY said:


> Hi Jim;
> THANK YOU for your prompt Reply !!!!!
> Would you agree that 96 Volts is about right for a Bug, Given the weight of the Batteries.... About 85-90 pounds each, I would Guess. With the Curtis Controller I have , I can go up to 120 vols...Right now I have 8 12 Volt Batteries, I got these used... They seems to work fine... or for more Range could I use 12 8volt batteries, when I can raise the money ????
> THANK YOU Marty


When it comes to the batteries. It would not matter if you used 8 12v batteries or 12 8v batteries, unless the amp hour rating was different in the batteries. If both batteries had a 50 amp hour rating you would end up with 4.8 KWh of power. But, on the other hand if one of the batteries had a 100 amps then that pack would have 9.6 KWh of power.

Usually higher amp batteries are bigger and heavier.


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## BGT (Apr 7, 2008)

OK guys dont laugh.

How would one apply an electric vehicle idea to let say a Mac truck ( 18 wheeler )


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## JRP3 (Mar 7, 2008)

Lots of batteries, huge motor.


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## MrCrabs (Mar 7, 2008)

BGT said:


> OK guys dont laugh.
> 
> How would one apply an electric vehicle idea to let say a Mac truck ( 18 wheeler )



Probably like the hybrid desiel trains do, with a generator making electricity, and an electric traction motor, that can also do regen... along with a large battery bank/ultra capacitor bank to accept the power generated during regen.

The way the trains do it, is have 1 large generator in the "engine" car. Then have smaller electric motors at each wheel in each car.
The controller syncs all the motors together, and it gives the train insane starting torque, (which is needed with the weight they pull)
In case of really heavy loads/extra long trains, they can connect 2 "engine" cars to produce more electricity.

Imagine if your rig has 2 or 4 drive motors (1 for each rear axle, or 1 for each wheel) and the trailer has 2 or 4 motors. Then the rigs would be responsible for generating power, and controlling all the motors.


-Mods, feel free to move this to its own thread, since we hijacked the original topic with delusions of a hybrid Mac truck.


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## BGT (Apr 7, 2008)

Yes move it. I just bought a Peterbuilt project .


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## ronis108 (Dec 14, 2007)

MrCrabs said:


> Probably like the hybrid desiel trains do, with a generator making electricity, and an electric traction motor, that can also do regen... along with a large battery bank/ultra capacitor bank to accept the power generated during regen.
> 
> The way the trains do it, is have 1 large generator in the "engine" car. Then have smaller electric motors at each wheel in each car.
> The controller syncs all the motors together, and it gives the train insane starting torque, (which is needed with the weight they pull)
> ...


Or just put batteries and motor on the trailor, forget the tractor and send the trailor on its way! 

ron


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