# ICE & Electric motor HP



## Efiero (Feb 7, 2009)

Ok i want to know if you have a 100 hp electric motor is it the same as a 100 hp ICE why i ask is i see some posting that it will only take them like 5 HP to go 60 MPH now from what i know from racing and building car engines that the areodynamics and frontal area plus roll risistance will cost you more HP than that on an ICE based on a production car so whats the deal


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## Guest (Feb 15, 2009)

Efiero said:


> Ok i want to know if you have a 100 hp electric motor is it the same as a 100 hp ICE why i ask is i see some posting that it will only take them like 5 HP to go 60 MPH now from what i know from racing and building car engines that the areodynamics and frontal area plus roll risistance will cost you more HP than that on an ICE based on a production car so whats the deal


Electric motors and ICE engines are not rated the same. That 5 hp DC motor is continuous HP where that 100 hp engine is peak. That little 5 hp DC motor may actually make 50 hp depending upon the ability for that motor to accept high voltage and amps. It also has loads of torque at the beginning of the curve where that ICE has low torque and low HP and builds up. The electric just goes and has loads of power. You will be surprised when you get your first ride in a decent EV. Do not compare the Electric to an ICE. The dynamics are totally different. Do some research and you will find a better answer than I just gave. 

Pete : )


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## Efiero (Feb 7, 2009)

ok i see what your saying but how can it take say 20 HP to push a car 60 MPH with a ICE and Guys are saying it only takes 5 HP with an electric motor this cant be true the car takes the same energy to go the same speed with the same car


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## Guest (Feb 15, 2009)

Efiero said:


> ok i see what your saying but how can it take say 20 HP to push a car 60 MPH with a ICE and Guys are saying it only takes 5 HP with an electric motor this cant be true the car takes the same energy to go the same speed with the same car


On average it takes 20 hp. You have a 100 ice that only uses 20 hp to keep the car moving. The electric motor is 5 hp continuous but you need 20 hp so you give a bit of juice and you bring that 5 hp up to 20. Remember you may actually have 50+ available to use so you can still move the vehicle. 

Like I said there are others that can better answer this. One of these days I am going to keep those answers and post them for all to read as prerequisite homework to building an ev. 

Pete : )


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## order99 (Sep 8, 2008)

There's one thing i've noticed about HP...

Most salesmen and distributors rate ICE motors by their maximum output, i.e. near the top of their performance peak. Running at that performance level will be...unpleasant for that poor engine after awhile.

Most EV dealers seem to rate their HP at their continuous output-i.e. the level at which they could run for an hour or more easily. A 5HP DC motor might actually put out 12-16HP or so when you floor it, and proper cooling might get you even more.

Both ICE and EV motors have recommended RPM ratings-if you can find more detailed analysis of a particular model you might find ratings of 'X HP at 1100 RPM' or 'X Torque at 900RPM'. Just to make it more confusing you might get Compression Ratings at X etc for ICE and so forth-no, i'm not a very Technical person, why do you ask? 

Then you've got differing efficiency profiles-ICE gets really fuel-efficient at low RPM as long as it isn't straining too much, while EV seems to waste less of it energy at the high bands...

Okay, now MY head hurts.


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## Efiero (Feb 7, 2009)

I understand that a 5 HP electric motor will put out more power pleas read what I asked I will say it again How can 5 hp push a car the same speed as 20 Hp its not a trick ? lets say i use my fiero it takes 25 HP to go 75 Mph with a ICE so how many HP will i take with an electric motor It should be 25 hp to go 75 mph correct but some one told me thats not right and that is bull it takes the same amount of energy for the same car to go a certan speed nomatter if it fart power or electric or gas


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## MalcolmB (Jun 10, 2008)

20 horsepower at the wheels is exactly the same whether it's produced by an ICE or electric motor. In two cars that are otherwise identical it will get you to exactly the same speed. The differences in horsepower numbers just come differences in the way engines and motors are rated, as the guys above explained. From what I've heard it's difficult to measure the performance of an electric vehicle using a conventional dynamometer, so there is very little data for making a direct comparison.


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## Efiero (Feb 7, 2009)

Ok now that that is claer then to find out how many watts it take to go like 75MPH i take 25 HP X 746 i think that 746 is how many watts in 1 HP that is 18650 watts now the 18650 watts is how many watts i would burn in 1 hour of driving at 75 right so to find my watts per mile i need to divide it by the miles traveld in one hour correct 18650 divided by 75 = 248.6666 watt hours per mile ok if i did this wrong pleas show me what i did wrong i had one guy tell me its wrong but he dint show me what or explain so i think he was full of it


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## GTWCMT (Jan 22, 2009)

Efiero said:


> Ok now that that is claer then to find out how many watts it take to go like 75MPH i take 25 HP X 746 i think that 746 is how many watts in 1 HP that is 18650 watts now the 18650 watts is how many watts i would burn in 1 hour of driving at 75 right so to find my watts per mile i need to divide it by the miles traveld in one hour correct 18650 divided by 75 = 248.6666 watt hours per mile ok if i did this wrong pleas show me what i did wrong i had one guy tell me its wrong but he dint show me what or explain so i think he was full of it


 
I think youre going about this a bit backawards.
Its not the speed to speed but the weight to power requirements (1 watt = 1kg per meter per second)
then you take the math from the weight of the car.
Then take one mile, which is around 1060 meters and convert this into the speed ( best working in all metric - KPH) say that 70 MPH is 120kph

120 KPH is 120/60/=2 (2 meters per second)

then you take the weight and as its 2MPS you double it to get the power requirements.
a 1000KG car needs 1000watts X2 =2000 watts to go 70 and a HP is somthing like 768watts /2000=2.064HP

Now for moving, and what I think that your questions refers is torque, the eletrive motor has alot of torqure when starting so it can push a greater weight from stop over that of a ICE (which is why you rev up to pull off and you use a higher gear to allow the ICE to have the torqure and HPs to get you rolling)


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## DC Braveheart (Oct 12, 2008)

GTWCMT said:


> I think youre going about this a bit backawards.
> Its not the speed to speed but the weight to power requirements (1 watt = 1kg per meter per second)
> then you take the math from the weight of the car.
> Then take one mile, which is around 1060 meters and convert this into the speed ( best working in all metric - KPH) say that 70 MPH is 120kph
> ...


Sorry - but that is so wrong ... the power required to MAINTAIN a particular constant speed depends on the aerodynamic drag and rolling resistance on the vehicle - if I was not so lazy I'll pull out the equations but they are easy enough to find here and elsewhere on the internet. In particular the aerodynamic drag is proportional to the CUBE of the velocity (so to make a car keep a car going at DOUBLE the speed required EIGHT times the HP of the lower speed [ignoting rolling resistance]).

EDIT: OK - no need for me to be quite so lazy - have a look here http://www.metricmind.com/audi/3a-simple_sim.htm


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## Efiero (Feb 7, 2009)

but your nt taking into acount areodynamics that needs to be included like frontal area the wieght is part of the factor but is a small part and the best way to show what i am saying is take a 4x8 3/4 inch plywood lay it down go 70 not to bad on power to push it now stand it up it takes alot of power to push it 70 mph now so to just say a car wight is say 3000 LBS it will take X amount of power with out areodynamics I mean the fiero I am doing would only need like 7 HP but when it is all included it realy take 25 HP to go 75 MPH


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## GTWCMT (Jan 22, 2009)

yeah I was being lazy, but then your not quite right either as the air density would be a considerable factor, most drag is about 50mph to 80 is about 6 times greater, but below these speeds is different, there is a considerable amount of factoring that needs to be considered. Of course the 1w-1kg is in a vacuum.
if we did want to go into all the details then we would consider the tyres on the road surface the tyre pressures, wheel diameter, motor RPM, transmission, the mirror drag and cars rear drag, brake drag, battery surge and drop, umm and a whole long list or everything else.
but I feel that this would over complicate the matters of the questions basic's


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## Efiero (Feb 7, 2009)

I agree with what you are saying that tire pressure and others have an effect on it and the calculator i used on line did all that and it came up with 7 hp roll resistanc and 17. somthing HP for the areo so add the to together and i got 24. something so i rounded up to 25 Hp and i know the areodynamics forces is a curve


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## GTWCMT (Jan 22, 2009)

Efiero said:


> I agree with what you are saying that tire pressure and others have an effect on it and the calculator i used on line did all that and it came up with 7 hp roll resistanc and 17. somthing HP for the areo so add the to together and i got 24. something so i rounded up to 25 Hp and i know the areodynamics forces is a curve


well if you have 7hp rolling resistance, and 17HP for areo dynamics, these are both negatives. dont forget that there is nothing fixed for acceleration
(your 0-60mph) so the math I gave you has nothing on this infact generally speaking its around 26 secounds if you use the weight to power ratio.

But main drag from areo dynamics typically in a car is anything over 50mph with around 66%

If you looking at speed, you want to be looking at your RPM gear box and wheel radius, just do the math and see what you get RPM to RPM (at the wheel) but its should rougthly be the same as a gas engine, yet you should be able to get some more with higher RPM motors. This mean that you will need higher voltages to get there, I would suggest 124 volt min


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## Efiero (Feb 7, 2009)

Well i have learnd a few things and the guys that think there gona go 65 mph with 4 or 5 HP are all wet I think they could make a super light aredynamic car that would use low power but just not that low for real world use


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## Duncan (Dec 8, 2008)

Hi Efiero,
Some cars can do 65 mph on 5 HP - think solar racers, small light very very low drag
25 HP is a more sensible number for a normal car.

At any speed you need enough power to counter the drag and rolling Resistance - any extra power you have is available for acceleration

The thing about an ICE engine is that it has full power available at peak revs - 6000rpm or so

At 3000 rpm it will have just over half of the power available

An electric motor has most of its power available all the time

most people don't drop two gears to accelerate, they just floor it 
If they do this at 3000 rpm in their 100 HP car they have 50 HP to play with
in a 60 HP electric you have 60 HP all the time

If you are using 30 HP for drag + rolling resistance the 100 HP IC car has 20 HP left for acceleration and the 60 HP Electric has 30 HP available

If you just stomp it which one is faster?

On the other hand if you drive the 100 HP car at peak revs it will blow the electric away


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## Efiero (Feb 7, 2009)

well i did say a car for the real world not a solar racer one seat bicycle tire non practical use car and a steady speed of 75 MPH not acceleration . I thought the torque of the electric motor is constant not the HP as voltage is applied the HP go's up. HP is based on torque & rpm so HP is not the same at all rpm


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## JRP3 (Mar 7, 2008)

Efiero said:


> well i did say a car for the real world not a solar racer one seat bicycle tire non practical use car and a steady speed of 75 MPH not acceleration . I thought the torque of the electric motor is constant not the HP as voltage is applied the HP go's up. HP is based on torque & rpm so HP is not the same at all rpm


Actually torque drops off a lot in a DC motor as RPM's climb. Notice how torque and HP drop in this Warp8 chart:
http://www.go-ev.com/images/003_12_WarP_8_SpreadSheet.jpg


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## Efiero (Feb 7, 2009)

the hp and torqu both go down as the rpm clime but if you started at O rpm you could or would have the 70 ftlbs of torque but o HP due to there are no rpm .

*To calculate the horsepower of a motor when the speed and torque are known, apply this formula:*
*HP = rpm x T(torque)
 5252(constant)*​


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## JRP3 (Mar 7, 2008)

Yes but I was replying to this statement:


Efiero said:


> I thought the torque of the electric motor is constant not the HP as voltage is applied the HP go's up.


The torque of an electric motor is not constant, it's just very high at lower RPMs, and at a certain point it drops low enough that HP stops increasing as well. This is more pronounced in series DC motors, AC motors hold their torque longer and usually have higher RPM ranges.


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## Bowser330 (Jun 15, 2008)

JRP3 said:


> Yes but I was replying to this statement:
> 
> The torque of an electric motor is not constant, it's just very high at lower RPMs, and at a certain point it drops low enough that HP stops increasing as well. This is more pronounced in series DC motors, AC motors hold their torque longer and usually have higher RPM ranges.


JRP3,

What about in a higher voltage DC situation? 

Would the increase in voltage make the motor capable of pulling higher amps at higher rpm? Thus making more of the power available at one ratio....


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## JRP3 (Mar 7, 2008)

Higher voltage allows the same power with less amperage, or more power at the same amperage, power being amps x volts, or watts. I think it's better to look at watts than just torque. Pulling 50 amps at 300 volts is more power than 100 amps at 100 volts. Now, is there any difference in performance between 50 amps at 300 volts and 100 amps at 150 volts, with both totaling 15Kw, other than heat losses, I'm not sure.


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## Bowser330 (Jun 15, 2008)

JRP3 said:


> Higher voltage allows the same power with less amperage, or more power at the same amperage, power being amps x volts, or watts. I think it's better to look at watts than just torque. Pulling 50 amps at 300 volts is more power than 100 amps at 100 volts. Now, is there any difference in performance between 50 amps at 300 volts and 100 amps at 150 volts, with both totaling 15Kw, other than heat losses, I'm not sure.


But in reagrds to rpm, how does a higher or lower voltage affect the power at rpm?


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## JRP3 (Mar 7, 2008)

That's an interesting question since higher voltage should mean higher RPM's. I think a 48 volt pack at full throttle should turn the same motor the same RPM's as a 96 volt pack at half throttle, but since the 96 volt half throttle isn't really 48 volts but 96 volts pulsed are the amps cut in half?


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## Efiero (Feb 7, 2009)

thought i would post this site good for figuring out how much power you will need
http://ecomodder.com/forum/tool-aero-rolling-resistance.php


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## Bowser330 (Jun 15, 2008)

very cool calculator, thanks!


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## Efiero (Feb 7, 2009)

Glad to help thats what we are all on the forum for


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## Bowser330 (Jun 15, 2008)

JRP3 said:


> That's an interesting question since higher voltage should mean higher RPM's. I think a 48 volt pack at full throttle should turn the same motor the same RPM's as a 96 volt pack at half throttle, but since the 96 volt half throttle isn't really 48 volts but 96 volts pulsed are the amps cut in half?


I think you are correct there...

But what I was getting at, and I may be way off on this, but i thought i read that a higher voltage could pull the same amount of amps for more rpm than a lower voltage setup.. so...for example...

if... 
*120V *can pull 500A from 0-*3000rpm* (motor)

then can...
*240V* can pull 500A from 0-*6000rpm* (motor)??


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## Gavin1977 (Sep 2, 2008)

JRP3 said:


> Higher voltage allows the same power with less amperage, or more power at the same amperage, power being amps x volts, or watts. I think it's better to look at watts than just torque. Pulling 50 amps at 300 volts is more power than 100 amps at 100 volts. Now, is there any difference in performance between 50 amps at 300 volts and 100 amps at 150 volts, with both totaling 15Kw, other than heat losses, I'm not sure.


You have to be a bit careful here not to confuse battery volts & amps with motor volts and amps. If you take a motor and double the voltage it will double its speed (in theory) and take a heck of a lot more amps

I would guess that a higher pack voltage would be better, as less current = less I2R losses in the battery cable, and also allows for higher motor speed (depending on your setup) Once passed your controller however, what the motor sees is more or less identical regardless of your battery setup (As long as you're haven't hit your voltage limit)


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## Gavin1977 (Sep 2, 2008)

Bowser330 said:


> I think you are correct there...
> 
> But what I was getting at, and I may be way off on this, but i thought i read that a higher voltage could pull the same amount of amps for more rpm than a lower voltage setup.. so...for example...
> 
> ...


Yes, as long as your motor/controller/gearbox setup allowed your motor to get up to the higher speeds.

What i mean by this is that you have to look at what's the limiting factor in your setup under different scenarios. ie, if you have the vehicle going flat-out and its reached its top speed, then at this speed, you measure the motor voltage and amps. If the motor voltage is at 120v, and the current is say 300A, then yes a higher voltage battery pack would allow you to go faster. If however the motor voltage is at 90V, and your motor amps are at current limit (In your example, 500A) then for this situation, adding a higher voltage pack will make no difference, as your battery voltage is not what's limiting you.

Bear in mind, thats all theoretical, in practice, your battery voltage will sag quite a bit, and the motor voltage wont quite reach the controller voltage. Also I have no real world experience with electric cars, all the motor/controller stuff i do for a living is much smaller scale. Hope thats of some help


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## JRP3 (Mar 7, 2008)

Gavin1977 said:


> You have to be a bit careful here not to confuse battery volts & amps with motor volts and amps. If you take a motor and double the voltage it will double its speed (in theory) and take a heck of a lot more amps


How will it take more amps? The current capacity of the motor should stay the same, but the higher voltage allows more power, wattage, at the same amperage. A motor that can handle 500 amps at 120 volts can't handle 800 amps at 170 volts, it's still stuck at 500 amps.


> I would guess that a higher pack voltage would be better, as less current = less I2R losses in the battery cable, and also allows for higher motor speed (depending on your setup)


Yes but in regards to torque is there a difference between 50 amps at 300 volts and 100 amps at 150 volts since the wattage is the same, 15 KW?


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## Efiero (Feb 7, 2009)

? is there a way to figure out how many amps you can put to the motor with out the specs like by wire size


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## piotrsko (Dec 9, 2007)

yes wire gauge charts for current exist, but you will need to factor in temperature rise because if you feed in too much current then the wire gets too hot in some location and melts. melting wire makes smoke, which causes motor to stop turning. I believe the wire paint insulation is rated for 300 degrees.

For example: a wire the size of the human hair will conduct 10 amps while immersed in liquid hydrogen, or about 1/10 amp at room temp.

rule of thumb: current X voltage = watts watts divided by 726 is the formula for HP equivalents, but electric HP and ICE Hp aren't really the same thing.


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## JRP3 (Mar 7, 2008)

Most forklift motors are class H insulation which is rated to 180 degrees Celsius, 356 Fahrenheit.


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## Gavin1977 (Sep 2, 2008)

JRP3 said:


> How will it take more amps? The current capacity of the motor should stay the same, but the higher voltage allows more power, wattage, at the same amperage. A motor that can handle 500 amps at 120 volts can't handle 800 amps at 170 volts, it's still stuck at 500 amps.?


Hi JPR3, I made a bit of an assumption that the motor was connected to a load & that as it sped up, the torque required to turn the load would also go up, hence the current. Depending on the application, this isn’t necessarily the case. As for it being stuck at 500Amps if you increased the voltage, that is because the controller is current limiting it, and if, for a particular load, the controller is at its current limit, then increasing the battery voltage isn't going to make any difference as the controller will still be in current limit. Remember, the motor and controller is essentially a current controlled device.



JRP3 said:


> Yes but in regards to torque is there a difference between 50 amps at 300 volts and 100 amps at 150 volts since the wattage is the same, 15 KW?


Again, is this battery or motor volts & amps? If battery, then I would assume the torque would be the same, as at the controller side, the voltage and current would be the same.

If its motor volts and amps, then at the motor, the 100amps would be generating more torque, but 300V motor would be spinning much faster. If you put this through a gearbox to bring the final drive down to that of the 150V motor, then the torque would now be the same at the final output (ignoring losses)

Does that make any sense? probably not, i'm not very good at explaining myself.


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## Efiero (Feb 7, 2009)

I think you are correct the geraring to get the same rpm at the wheel would be lower so it would make it like it had the same torque of a lower rpm higher torque motor only thing is the lower the gear might resault in bigger loss but it might not either . I am running 2 motors and will be in sieries this way i will have what ever the amps the controler can handle going to both motors but i must up the volts due to each motor will only see half of the total voltage so 240 gives me 120 at each motor. I think that multi DC motors are the way to go run in sieries it gives you the same amps to each motor with out increasing the current draw frome the batteries but you must increas the voltage to get rpms back i think it will be more efficant than one large motor with lower volts. if i could i would do 4 smaller motors in sieries 480 volts with like 500 amps


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## mattW (Sep 14, 2007)

I think it would be helpful here to introduce the concept of back emf. My understanding of why torque drops off in electric motors is due to back emf. Most of you know that most motors can also act as generators (series motors are more complex but bear with me). When a motor is spinning at a given RPM with current from the controller, the fact that the motor is spinning means that it actually acts as a generator trying to push current back against the controller. So lets say you are giving the motor 120V to give 3000rpm, the fact that the motor is spinning at 3000rpm creates a back voltage of maybe 50V. So the motor only 'sees' 70V. If the resistance of the wires in the motor is constant then at 0rpm you will have a full 120V to draw current through the motor, but at 3000rpm there is only 70V across the motor. So less current can flow and you get less torque.

If you upped your system voltage to say 144V then you would still get the same proportional back emf at 3000rpm (i.e. 50V) but now you have 144V -50V which is 94V. That higher voltage means you can draw the same amperage for longer. It would be at a higher rpm, maybe 3500rpm, when the motor would be at 70V. So you can keep drawing your peak amps for an extra 500rpm. After that the current starts dropping as the voltage drops (i assume according to V=IR) until the mechanical drag matches the power and the rpms stop going up.

I hope that makes sense, ask questions if it doesn't and correct me if I am mistaken.


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## mattW (Sep 14, 2007)

And in terms of ICE hp and electric hp there is no inherent difference. They are mechanically the same thing. The difference is mainly in the torque/power curves. The reason you can compare different ICE motors pretty well just by their peak power is because the power curves look more or less the same between models. But as an illustration even is you just think of a petrol (gas) car with big turbo lag and compare it with a diesel with the same peak power, they will both accelerate really differently... The diesel will pull out ahead early and the turbo car will accelerate more when the turbo spools. Same peak power, different acceleration. Electric cars are more like diesels but with even more torque down at low rpms so while the peak might be lower, the total power delivered will be more in an EV than a ICE of the same peak power.

So if you are wondering how the car will accelerate compared to an ICE then you need to know more than just the peak power. But if you want to know the top speed or how it will cruise at a set speed then there is a 1:1 comparison.


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## JRP3 (Mar 7, 2008)

Gavin1977 said:


> As for it being stuck at 500Amps if you increased the voltage, that is because the controller is current limiting it, and if, for a particular load, the controller is at its current limit, then increasing the battery voltage isn't going to make any difference as the controller will still be in current limit. Remember, the motor and controller is essentially a current controlled device.


 But the motor can physically only handle so many amps, regardless of the controller or voltage. Amps=heat and the motor can only deal with so much heat.


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## Efiero (Feb 7, 2009)

Ok ? what is the back EMF in more than one motor when there run in series or run parralell can you tell me any info


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## JRP3 (Mar 7, 2008)

I think the back EMF is specific to the motor and the power it is generating while running, regardless of the other motor or how it's wired to the pack. From the description it seems as if higher voltage reduces the effects of back EMF to some degree.


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## Efiero (Feb 7, 2009)

can i use capacitors or somthing to help reduce back EMF more


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## Anaerin (Feb 4, 2009)

Efiero said:


> can i use capacitors or somthing to help reduce back EMF more


The way I understand it, when you push power into the motor, it reaches a point where the motor starts "pushing back". Then your only option is to increase the power you're pushing in (increase the voltage). All putting capacitors into the line will do is create a "Lag" in your control as they charge and discharge. They can't "bleed off" the EMF power, as you're trying to put more power in at the same time. If you have a pipe that you're pushing water into from both ends, the end with the higher pressure is always going to win, even if you have a large sealed container in the middle. The container (The capacitors, in this case) will "fill" with pressure until it has somewhere to release that pressure, which will be into the motor if the EMF backs off (IE, the load goes away), or into your controller if you back off the power (And if the Capacitor hasn't already blown because you're driving it backwards).

IANAEE, however, so my understanding could be faulty on this.


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## Bowser330 (Jun 15, 2008)

mattW said:


> I think it would be helpful here to introduce the concept of back emf. My understanding of why torque drops off in electric motors is due to back emf. Most of you know that most motors can also act as generators (series motors are more complex but bear with me). When a motor is spinning at a given RPM with current from the controller, the fact that the motor is spinning means that it actually acts as a generator trying to push current back against the controller. So lets say you are giving the motor 120V to give 3000rpm, the fact that the motor is spinning at 3000rpm creates a back voltage of maybe 50V. So the motor only 'sees' 70V. If the resistance of the wires in the motor is constant then at 0rpm you will have a full 120V to draw current through the motor, but at 3000rpm there is only 70V across the motor. So less current can flow and you get less torque.
> 
> If you upped your system voltage to say 144V then you would still get the same proportional back emf at 3000rpm (i.e. 50V) but now you have 144V -50V which is 94V. That higher voltage means you can draw the same amperage for longer. It would be at a higher rpm, maybe 3500rpm, when the motor would be at 70V. So you can keep drawing your peak amps for an extra 500rpm. After that the current starts dropping as the voltage drops (i assume according to V=IR) until the mechanical drag matches the power and the rpms stop going up.
> 
> I hope that makes sense, ask questions if it doesn't and correct me if I am mistaken.


Excellent example!!!

So....lets go one further...at 250V (using an interpoled DC motor) you would still have 200V after back emf and the 3krpm would increase to somewhere close 5-6Krpm....

So if 800A was the peak amps.... you could draw 800A all the way up to 5000rpm...

200V * 800A = 160kw = 214hp

So with a 5:1 ratio....0-1000rpm = 0-90mph??? (with standard 16" tire)...and the entire time you have access to 214hp, from 0mph-90mph.......


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## Efiero (Feb 7, 2009)

yes you would have 214 HP I wonder what the torque would be thats what accelerats you but with 5 to 1 gearing it should be pretty quick


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## Efiero (Feb 7, 2009)

I will be using a automatic trany minus the toque converter i will be using a front pump & drive like in this pic this one is for a powerglide. 
Geting rid of the torque converter should pick up the efficiency of the trany to i would think equal or better than a standard Oh for those who are intrested TCI makes drives for turbo 350 & 400 and i think C6 ,727


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## JRP3 (Mar 7, 2008)

Bowser330 said:


> So if 800A was the peak amps.... you could draw 800A all the way up to 5000rpm...
> 
> 200V * 800A = 160kw = 214hp


I don't think so. As motor speed increases so does back EMF. Not to mention if 800 amps is your peak amps that's only momentary and the motor and controller couldn't handle a constant 800 amps.


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## Efiero (Feb 7, 2009)

I keep hearing things from you JRP3 that makes me like more than one motor and run in series every thing from the controller to arcing of the brushes on DC motors that is. I would think that multy small motors would be able to turn higher rpms than one big havey motor plus i would think a smaller motor would rev faster than a big one due to the diameter


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## JRP3 (Mar 7, 2008)

Multiple motors have their own problems. As we know voltage to each motor is less, which means amp draw is higher, which means we lose energy through heat, so it's less efficient, and a motor can handle only so many amps. The lower voltage probably means greater back EMF effects, and lower voltage means they won't turn as fast. The RPM max of any brushed motor has more to do with the ability of the commutator to stay together under high centrifugal loads, which has more to do with the way they are constructed. Smaller motors have smaller brush and comm area which limits how much power they can handle. Then there is the cost and complexity of multiple motors and controllers. There are always compromises.


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## JRP3 (Mar 7, 2008)

Here's is a relevant post by Ian Hooper from the EVDL:


> .......the rev limit on most motors is due to the
> centripetal forces pulling the armature apart at high revolutions....
> 
> The best way to avoid a transmisison (in my opinion) is to use two
> ...


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## Efiero (Feb 7, 2009)

but i said i would put duble the volts to it so you are right backe up there with the volts so you will end up using less amps i dont think it will be less efficient i think it would be like one biger motor with 120 volts to it but you will be using 240 volts devide by 2 from what i understand that way each motor see's 120 volts but the amps dont need to be dubled because it is runing in series so you will need less amps. ? advancing the brush timing takes away low rpm torque if so why not make it so the brush timing can be added as ther rpm go's up it wouldnt be that hard for some one with the tools you would run like 2 degree's advance at like 500 rpm and it would go to like 15 advanced at 5000 rpm


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## Bowser330 (Jun 15, 2008)

JRP3 said:


> I don't think so. As motor speed increases so does back EMF. Not to mention if 800 amps is your peak amps that's only momentary and the motor and controller couldn't handle a constant 800 amps.


Hmmmm Ok so the back emf wouldnt be the 50 that was mentioned in the example...If it goes up as speed goes up... is it proportional?

So 50V of back EMF at 3000rpm and 100V at 6000rpm?


I cant wait till I can start testing this stuff....


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## DC Braveheart (Oct 12, 2008)

Bowser330 said:


> Hmmmm Ok so the back emf wouldnt be the 50 that was mentioned in the example...If it goes up as speed goes up... is it proportional?
> 
> So 50V of back EMF at 3000rpm and 100V at 6000rpm?
> 
> ...


I believe that is correct - it's a concept known as "RPM per volt" - basically for each volt applied an electic motor will spin at a constant RPM (say 1V = 50RPM, 2V=100RPM, 100V=5000RPM). 

The reverse applies to back-EMF - so if a motor's RPM per volt is 100, then when spinning at 1000RPM it's producing 10V back-EMF, and at 5000 RPM, back-EMF is 50V. You motor will stop producing torque when the back-EMF is the same as the voltage being applied by the controller (torque is proportional to current and current stops flowing when controller voltage is the same as back-EMF).

(Note this is what I picked up from reading about BLDC motors here - http://www.southernsoaringclub.org.za/articles.html - I believe it applies to other motor types too).


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## Efiero (Feb 7, 2009)

Ok then ? if i run 2 motors in series and turn 3000 rpm is it 30 volts back EMF or 60 volts 2X 30


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## mattW (Sep 14, 2007)

Efiero said:


> Ok then ? if i run 2 motors in series and turn 3000 rpm is it 30 volts back EMF or 60 volts 2X 30


You will get back emf from both motors, so they will add, but it they would be smaller so the net effect would be about the same as one big motor.


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## JRP3 (Mar 7, 2008)

Yes each motor produces it's own back EMF so in your example 60.


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## JRP3 (Mar 7, 2008)

Efiero said:


> advancing the brush timing takes away low rpm torque if so why not make it so the brush timing can be added as ther rpm go's up it wouldnt be that hard for some one with the tools you would run like 2 degree's advance at like 500 rpm and it would go to like 15 advanced at 5000 rpm


Jim Husted at hitorqueelectric.com has made adjustable advance rings http://hitorqueelectric.com/gallery/v/Variable+timing+rings/


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## Efiero (Feb 7, 2009)

Nice i like the timing now they need to come out with the servo to adjust timing according to load and rpm for best prefomance from the motor at all times or centrifugal weights to run it


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## Efiero (Feb 7, 2009)

? running motors in series or paralell ok if i put 2 motors in paralell both will see full voltage but half the amps so hi rpm low torque running in series both motors will se all the amps and half the voltage so high torque low rpm . the real trick is knowing the rpms the motors will have peak HP . I am looking at this like a 454 chevy VS 283 chevy high rpm Vs high torque. the high torque will pull a higher gear and the low torque a lower gear. so more fuel = higher amps or more volts= higher efficency with motors in parralell you are going to hit rpm and voltage limits faster and with series it hits amp limits faster


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## JRP3 (Mar 7, 2008)

Efiero said:


> Nice i like the timing now they need to come out with the servo to adjust timing according to load and rpm for best prefomance from the motor at all times or centrifugal weights to run it


Since brush timing needs to advance with voltage a simple servo controlled by the voltage going to the motor should work.


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## JRP3 (Mar 7, 2008)

Efiero said:


> ? running motors in series or paralell ok if i put 2 motors in paralell both will see full voltage but half the amps so hi rpm low torque running in series both motors will se all the amps and half the voltage so high torque low rpm . the real trick is knowing the rpms the motors will have peak HP .


One problem with your motors is I doubt they could handle the full pack voltage of 240 volts when paralleled.


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## Efiero (Feb 7, 2009)

i wouldnt run in parallel because to bring the torque up you need to add amps and amps drain batteries but if you run in series like i want, if you put 1 amp to the motors both see that 1 amp but if you put 2 volts at the motors they each will see 1 volt. I think my motors might be able to take 150 Volts max and not sure how many amps but if i get a controler that can do 300 volts and 500 amps then i will have 150000 watts of power. Each motor will only see 150 volts if 300 volts are put in but each will see the 500 amps max . if i ran it in parallel with my motors i could go maybe 150 volts and i would need to go to 1000 amps to get the same power but it would drain the batteries faster


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## Gavin1977 (Sep 2, 2008)

Efiero said:


> i wouldnt run in parallel because to bring the torque up you need to add amps and amps drain batteries but if you run in series like i want, if you put 1 amp to the motors both see that 1 amp but if you put 2 volts at the motors they each will see 1 volt. I think my motors might be able to take 150 Volts max and not sure how many amps but if i get a controler that can do 300 volts and 500 amps then i will have 150000 watts of power. Each motor will only see 150 volts if 300 volts are put in but each will see the 500 amps max . if i ran it in parallel with my motors i could go maybe 150 volts and i would need to go to 1000 amps to get the same power but it would drain the batteries faster


It wouldnt drain the batteries any quicker as the battery current would be the same in either case. (Give or take a little as were not in an ideal world  )


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## Efiero (Feb 7, 2009)

I thought that current = AMPS if this is so then 500 amps drains the batteries slower than 1000 amps


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## Gavin1977 (Sep 2, 2008)

Efiero said:


> I thought that current = AMPS if this is so then 500 amps drains the batteries slower than 1000 amps


Correct.

But assuming that you have the same pack voltage in either case, the Battery amps would be about the same.

The controller (very crude explaination) rapidly switches the motor on and off to give you the correct output voltage. So if for example, you have a 300volt battery pack, but your motors are running at 150v, 1000A, then the controller will be running at 50% duty cycle, that is, on and off for the same amount of time. The controller would pull 1000A out of the batteries for 1/2 the time, therefore, on average it is 500A. Also the controller has capacitors at the input to smooth these current gulps, so the batteries see closer to a 500A constant current, rather than 1000A gulps.

Gav


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## Efiero (Feb 7, 2009)

I see what you are saying is that it sees all the volts and amps at all times but how long is the switch on so at 50 precent it on half the time so it like seeing halfe of the total but what do's that have to do with having a battery pack that put out 300 volts and 500 amps vs 150 volts 1000 amps they both have the same watts but the 300 volt 500 amps is more efficient less curent draw . with the dual motor setup run in series at full throtel max draw on the batteris will be a full 500 amps each motor will see the 500 amps now the volts will be a full 300 but becuas it is in series each motor will see 150 volts . If I run in parallel and do it with 150 volts each motor will see 150 volts and i draw 1000 amps each motor will see 500 amps and last i knew from reading in this forum that large current draw made biger voltage drop more heat both are ineffeciency plus 500 draw is less than 1000 but will the batteries go the same distance if the same amout of watt hours are in the batterie pack well if the 300 volts 500 amps is more efficecnt it shoud go a little further


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## Gavin1977 (Sep 2, 2008)

EfieroOK I see what you are doing now, my previous posts assumed the same battery configuration for your two setups, and was basically just some theory on motor controllers, rather than practical stuff.

I would be inclined to agree with you, that in your case, a series setup would be more efficient, as you will have lower currents in your motor cables, hence less heat loss.


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## JRP3 (Mar 7, 2008)

Gavin1977 said:


> I would be inclined to agree with you, that in your case, a series setup would be more efficient, as you will have lower currents in your motor cables, hence less heat loss.


 Assuming the same pack voltage, isn't the opposite true? Series motors see full current and half voltage, parallel motors see full voltage but half current. That's why using series/parallel switching of the pack is best, high current at lower speed for torque but high voltage when switched to parallel for higher speed.


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## Efiero (Feb 7, 2009)

when runing the motors in series you get duble the torque for the 500 amps because both motors see the 500 amps and in parallel they only see 250 amps each so each motor produce half the torque so less power is made unless you draw 1000 amps but in the series you have to go to 300 volts so each motor see's 150


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## Efiero (Feb 7, 2009)

I thought i would tell what i am thinking i am thinking if you run in series you get more torque for each motor you add with out drawing any more amps but to keep the rpms you must put more volts to it so as the torque increases you will use less amps but it will still be the same watts due to it is a higher voltage in the battery pack . basicly lets say you have 1 motor and to go 65 MPH it takes 200 WH of work per mile so if you have 150 volts to the motor then you need 1.333 amps now lets take and put 4 motors and you put 150 volts to each of the motors so you need 600 volts total so 200 wh devided by 600 = .3333 amps are needed now each motor is making 50 wh worth of work x 4 = 200 wh I hope this is correct in my thinking


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## bipolar (Mar 11, 2009)

Here is what you going to find;

Firstly, in regards to EMF, when your motor spins, it acts like a generator and produces an 'EMF'. This becomes the 'resistive' force upon which applied voltage builds. Rotation will increase until the produced 'counter electromotive force' equals the applied force, less losses. EMF is directly proportional to rotor speed.

At no load full speed, your current draw will be the difference of EMF to applied voltage / internal winding resistance.

Secondly, in regards to series connected DC motors. What happens if both motors are spinning at the same speed and both delivering the same EMF for equal votage drop, when for some reason one of the motors is slowed (ie by applied load). The motor that begins to slow will now have a reduction in EMF. This effectively increases the voltage drop across the other motor, causing it to increase in speed to counter the applied voltage. Your net result is a loss of motor speed control. In addition, if your controller was double the hp of either motor (in an attempt to run two motors equally), you would likely fry one motor in short order.


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## JRP3 (Mar 7, 2008)

bipolar said:


> Secondly, in regards to series connected DC motors. What happens if both motors are spinning at the same speed and both delivering the same EMF for equal votage drop, when for some reason one of the motors is slowed (ie by applied load). The motor that begins to slow will now have a reduction in EMF. This effectively increases the voltage drop across the other motor, causing it to increase in speed to counter the applied voltage. Your net result is a loss of motor speed control. In addition, if your controller was double the hp of either motor (in an attempt to run two motors equally), you would likely fry one motor in short order.


In this case the motors are physically connected so will always see the same load.


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## bipolar (Mar 11, 2009)

Duh, I must have been thinking about that electric airplane


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## barntechsolar (Mar 5, 2009)

Efiero said:


> Ok i want to know if you have a 100 hp electric motor is it the same as a 100 hp ICE why i ask is i see some posting that it will only take them like 5 HP to go 60 MPH now from what i know from racing and building car engines that the areodynamics and frontal area plus roll risistance will cost you more HP than that on an ICE based on a production car so whats the deal


 
If memory serves me right, a 1 hp electric motor is equal to a 3 hp ICE. My motorcycle conversion has what the owners book indicates, B&S Etek 6 hp cont 15 hp peak @ 48 volts In short it is 18 hp and 45 hp equivalent. In my motorcycle conversion, can be seen here www.evalbum.com/2196 has no tranny, just direct drive. Just try that with your Infernal Combustion Engine. Yes, in the pics there is an engine and it powers an alternator for anytime anywhere battery charging. Before you laugh yourself silly, fuel consumption is 100 kilometers per liter.


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## bipolar (Mar 11, 2009)

Your thoughts on the original post are correct though. Moving a vehicle along that requires torque at some speed can be calculated to horsepower. That will be the same requirement independant on the device supplying the power.

The difference of course is how the prime mover is rated. An ICE's hp is typically rated at some high rpm, while the motor is rated at a different speed. 

If you check the ICE's hp rating at comparible speeds, you will come closer to the answer. Don't forget also that an ICE's torque/hp falls rapidly at low speeds


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