# why is it so difficult for electric car to have high top speed ?



## EdwardR (Jun 22, 2010)

Greeting folks 

I just signup for this forum as i'm truly curious about this, and i can't find a clear answer anywhere. 

1. i look at the spec of most electric car, the acceleration is just staggering, yes, but top speed seem to be somewhat, mediocre. Why is this so ?

2. If the above has to do with electric motor limitation, can't we just slab in a set of transmission to improve it ?, and if this is possible, why big name electric car company hasn't already done it ? 

3. Can an electric motor be designed to excel at certain application than others ? for instance, can we design electric motor that will be suitable for highway cruise, but not so much for city commune and vice versa ?

4. If the above is true, can't we just have 2 separate motors in one electric car and switch between them when driving condition changed ? 

I'm no engineer and my physic knowledge is limited to just high school level, but i did some self studies and possess some knowledge regarding the topic

I hope someone in here could give me some pointers

Thanks


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## major (Apr 4, 2008)

I don't think it is so difficult, just expensive.


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## DavidDymaxion (Dec 1, 2008)

The Buckeye Bullet went 315 mph on the Salt Flats! The picture below shows my electric conversion getting pushed at 1 mph on the Salt Flats!

Power usage jumps up very quickly with speed, and cost also jumps up very quickly. I think that's the biggest reason most electric cars are designed with the bare minimum top speed needed, to save money or for better range for the money.

A related reason is it is much easier to dump a lot of power for 10 or 15 seconds for a drag racer, rather than the minutes required for land speed racing -- so electric motorsports have tended to emphasize drag racing over road racing or land speed racing. With modern lithium batteries this is starting to turn around, for instance with the TTXGP series, as well as Ohio State and BYU running electric streamliners on the Salt Flats this summer.

I have a performance simulation http://explodingdinosaurs.com/elandspeedsim/ . After this summer hopefully I'll be able to say the sims were accurate!

For 2.: The Buckeye Bullet used a 5 speed transmission. Electrics have very broad torque curves compared to a gasoline engine, so not as many gears are needed -- one gear is often enough to do the job.

For 3.: Yes, electric motors can be designed for different extremes. You can make a short term motor lighter, as it doesn't run long enough to overheat. You can tweak various motor parameters to make them better at high speed or low speed, such as spacings or brush timing.

For 4.: People looking for great performance over a large rpm range usually do AC motors -- they'll have about twice the rpm range of a typical, cheaper DC conversion.



EdwardR said:


> Greeting folks
> 
> I just signup for this forum as i'm truly curious about this, and i can't find a clear answer anywhere.
> 
> ...


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## Qer (May 7, 2008)

DavidDymaxion said:


> For 4.: People looking for great performance over a large rpm range usually do AC motors -- they'll have about twice the rpm range of a typical, cheaper DC conversion.


I've heard this so often now that I'm tempted to call it an urban myth. 

Let's say that we have two systems, one AC and one DC, that both can provide 100 kW peak power and that the AC system does this at 10k RPM while the DC system peaks at 5k RPM. Since power is the result of RPM multiplied with torque this gives that when peak power is reached the DC system might be running at half the RPM but instead gets twice the torque! Now, it's not practical to connect the motors directly to the wheels since a typical car wheel turns at some hundred RPM:s, which will make the motor run rather inefficiently. This means you will need a gear box. Even if you go direct drive, you will need something to gear down the RPM to sane levels, even if you're doing drag racing.

So, a gear box pretty much trades RPM for torque, giving:

RPMin * TORQUEin = RPMout * TORQUEout

This is pretty much similar to how a controller trades voltage for current, btw. Must be because it's physics. 

Anyway, let's say we gear down the DC-system with a factor four (numbers out of a hat here) and the AC-system with a factor eight total (since it spins twice as fast), we'll end up with the exact same RPM and Torque numbers since the two systems have the same peak power! And since both systems can give full torque (or at least pretty much torque in the AC-system depending on the controller algorithm) from 0 RPM there's no (or very little) difference between the two technologies when it comes to RPM range after the gear box!

The differences in performance comes from other things, mainly the controller and the pack and I can't help thinking that the DC-systems bad reputation comes from the 144 Volt lead-acid era when people had a problem to get the DC-system reach the high RPM's because the lead-acid sagged too much and the trusty, old Curtis went into overtemp cutback as soon as you were trying to have even the slightest wee bit of fun.

Sure, keep the old myths alive if it makes you happy, but if it were anything but a myth the EV drag racing wouldn't be ruled by DC.


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## TX_Dj (Jul 25, 2008)

I concur, not difficult, just expensive.

Furthermore, not legal... so you're talking about a racing vehicle if you're talking about going much faster than posted speed limits, so cost would be very little factor since racing costs real money.

KillaCycle does over 170 mph in the quarter mile. It is not a cheap motorcycle, probably about $250,000 invested.


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## Guest (Jun 23, 2010)

My Ghia would do better than 85 mph and that's with lead batteries. What's so bad about that? You looking to smoke the car next to you or just enjoy a brisk drive. I prefer to enjoy the brisk drive. 

Pete


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## aeroscott (Jan 5, 2008)

didn't GM do a EV1 special that did 180mph. I think the biggest problem is batteries , cost and weight in that order .Part of the weight problem is the C rating or how fast we can get the power out of the battery, so high discharge batteries are even more expensive say we filled up a streamlined 18 wheeler with 40,000 lbs of tesla cells (50 [email protected] 1000 lbs. that can pull 280 hp for about 10 minutes ) ,thats 40 x 50kwh = 2,000 kwh or 2mega watts or 11,200 hp for 10 minutes cost about 1 million dollars for the batteries . No one is even thinking of pushing big/ heavy and expensive batteries that are heavier then the cars they fit in . It can and will be done . its kind of like a rocket, fuel weighs more then the rocket


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## Bowser330 (Jun 15, 2008)

Qer said:


> I've heard this so often now that I'm tempted to call it an urban myth.
> 
> Let's say that we have two systems, one AC and one DC, that both can provide 100 kW peak power and that the AC system does this at 10k RPM while the DC system peaks at 5k RPM. Since power is the result of RPM multiplied with torque this gives that when peak power is reached the DC system might be running at half the RPM but instead gets twice the torque! Now, it's not practical to connect the motors directly to the wheels since a typical car wheel turns at some hundred RPM:s, which will make the motor run rather inefficiently. This means you will need a gear box. Even if you go direct drive, you will need something to gear down the RPM to sane levels, even if you're doing drag racing.
> 
> ...


+1

With all the new DC technology released, the days of the old reliable lead acid 144V setup is long gone...

The "New" DC setup includes something along the lines of...

300V lithium pack 1000A+ peak capable
DC motor built for high voltage (interpoles/kostov)
Controller capable of high voltage and high amperage

While still being cheaper overall...


I think people would be surprised how well a kostov 11" would do with 1000A capable controller and 300V of lithium batteries...


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## zwmaster (Nov 23, 2009)

Bowser330 said:


> +1
> 
> With all the new DC technology released, the days of the old reliable lead acid 144V setup is long gone...
> 
> ...


Bowser you got me again. I was thinking this would be a daily driver setup. Could I with my 280V and 100Ah expect more then that? 250V 11" Kostov if you remember.


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## 2cycle (Jul 2, 2009)

EdwardR said:


> Greeting folks
> 
> I just signup for this forum as i'm truly curious about this, and i can't find a clear answer anywhere.
> 
> ...


power to weight ratio mostly, but when your talking 200 mph your into aero pretty deep. 

The Tesla EV is a great example of what a "useful" powerband is. That car is set up to peak out around 120 mph-ish because it uses fairly high ratio final drive so it will accelerate well at a sacrifice to top speed, which is rather lame IMO. If it had gearing to support 160 mph it would make it much slower off the line, but that is where the brilliance comes in. Why produce a car that can go faster than what you will ever need it to go. It and many others will first be made to work well at normal driving speeds, once the cost comes down on the technology then we may see faster vehicles. Just try to find a 500 hp electric motor to use in an EV. A 500 hp gasser costs about $15K all said and done, with a warranty to boot. It will be a while before that happens in the DIY EV world so we can truely get rid of gassers for good in racing. 
I've been trying to get some customers of ours to switch to EV projects but they just will not give up the hp and light weight.


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## Qer (May 7, 2008)

zwmaster said:


> Bowser you got me again. I was thinking this would be a daily driver setup. Could I with my 280V and 100Ah expect more then that? 250V 11" Kostov if you remember.


If you have a 280 Volt pack, 100 Ah and don't want to go higher than 3C discharge rate (which is rather sane for most batteries) you'd still be able to get 1000 A motor current up to something like 70-80 Volt (sag included) which, if I remember correctly (and if I'm not guessing totally wrong ), would be something like 1900 RPM on a WarP 9" so probably a bit lower on a Kostov 11".

Above that the motor current will start to drop to avoid pulling too much current from the batteries. Provided, of course, we're talking about a controller that CAN limit the battery current. If it can't, sell it on e-bay and get one that can so you don't damage your pack.


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## 2cycle (Jul 2, 2009)

This is a speed calculator I found. Should pretty much answer your questions.
http://vlsicad.ucsd.edu/~sharma/Potpourri/perf_est_intro.html

Most EV's don't have enough hp to go fast, but they usually have enough torque to get the job done in town. Sometimes using different gearing can use your available torque better, but the fact remains to go faster you need more hp, or as electric motor guys will tell you "more torque at the same or higher rpm", they hate to admit that magical torque number they are so proud of is only part of the equation.


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## Qer (May 7, 2008)

2cycle said:


> Most EV's don't have enough hp to go fast, but they usually have enough torque to get the job done in town. Sometimes using different gearing can use your available torque better, but the fact remains to go faster you need more hp, or as electric motor guys will tell you "more torque at the same or higher rpm", they hate to admit that magical torque number they are so proud of is only part of the equation.


Um. I have several controller logs from vehicles going at highway speed. 60 mph doesn't seem to be impossible with as little as 128 Volt LiFePO4, so claiming that they're just good enough for town driving is a bit unfair...

That said, if you have an undersized controller it won't help what size of the pack or motor you have and most old fashion golf cart controllers on steroids simply won't cut it if you crave some serious performance.


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## JRP3 (Mar 7, 2008)

Qer said:


> Um. I have several controller logs from vehicles going at highway speed. 60 mph doesn't seem to be impossible with as little as 128 Volt LiFePO4, so claiming that they're just good enough for town driving is a bit unfair...


I can get 65 mph in second gear with my 115V nominal SE pack. I haven't tried a high speed run yet in higher gears. Truth is most people don't care too much about top speed since it's basically useless in the real world.


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## Bowser330 (Jun 15, 2008)

Qer said:


> If you have a 280 Volt pack, 100 Ah and don't want to go higher than 3C discharge rate (which is rather sane for most batteries) you'd still be able to get 1000 A motor current up to something like 70-80 Volt (sag included) which, if I remember correctly (and if I'm not guessing totally wrong ), would be something like 1900 RPM on a WarP 9" so probably a bit lower on a Kostov 11".
> 
> Above that the motor current will start to drop to avoid pulling too much current from the batteries. Provided, of course, we're talking about a controller that CAN limit the battery current. If it can't, sell it on e-bay and get one that can so you don't damage your pack.


+1

with the setup you have, as Qer has mentioned, its very daily drivable...how much above that?...well...that depends on what we dont know about your setup...

Do you have 100Ah of high performance high C rated batteries? or will you set the maximum battery current to 10C and risk damage? If so, you will have a VERY fast setup.

Do you have a controller that can handle 1000A safely and reliably? If you do not then you will not have that above average performance you might be looking for...

motor + batteries + controller, you have to have all three be quality pieces of equipment to get reliable high power performance...

you are off to a good start with an 11" kostov and 280V...the 100AH batteries are ok, better than lead acid for sure, just get a great controller and you will be off to the races!


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## The Toecutter (May 30, 2010)

EdwardR said:


> 1. i look at the spec of most electric car, the acceleration is just staggering, yes, but top speed seem to be somewhat, mediocre. Why is this so ?


There are many reasons for this.

With regard to OEM EVs and custom builts, it is typical for there to be only 1 gear because electric motors have a wide torque/power band. A single gear "transmission" is very durable and low maintenance, and in the US, the speed limit doesn't ever exceed 80 mph(except certain places in Montana where you can drive any speed you want, within reason, dependent upon factors like trafic volume or weather). Thus, it is most economical and energy efficient to design an EV with a top speed between 75 mph and 90 mph with a single speed gearbox; such gearing will allow said EV to have equivalent or slightly better acceleration than a gasoline powered car with a similar horsepower to weight ratio, only the EV never needs to change gears and achieving the best possible acceleration is effortless through its entire speed range.

With regard to hobbyist conversions that use series DC motors, top speed is often limited because the gearbox that came with the car stock is not optimized for the motor's powerband like it was for the gasoline engine that came with it. A 144V setup with an ADC 9" or Netgain 9" motor and a 1,000A controller, under the condition that it has a sufficiently powerful battery to maximize the power output with this setup, will reach its peak horsepower at around 3,000-3,500 rpm and decline dramatically after, even though the 1,000A from the controller will provide enough torque to embarass any V8. Thus, you could have an EV that makes 120 horsepower, accelerates like a 200 horsepower gasoline car with a comparable power to weight ratio, but ends up only being able to top out at 85 mph because in top gear, it might have its peak power available at 60 mph. With a much taller final drive ratio, this problem could be remedied and a conversion could easily be made to top 120 mph with such a setup, depending on its aerodynamics. With a more powerful setup, and appropriate gearing to go with it, 200+ mph for a street legal conversion is most definately possible, but it has yet to be done. Also, being that torque is proportional to the square of the current in a series wound DC motor, running a DC motor at its max output can overheat it in short order, so the motor's continuous current rating must be kept in mind when trying to maximize speed.

A gasoline car is typically given gears optimized for maximum top speed based on the car's horsepower, weight, aerodynamics, and other parameters. An electric car, depending on the drive system it has, will need to be similarly optimized; conversions by hobbyists often don't have that luxury due to financial limitations.

That being said, even a 72V conversion with a 400A Alltrax controller could be designed to reach 90+ mph, IF it had the appropriate gearing. It would get there very slowly, however. Most 72V conversions end up only being able to reach 50-60 mph or so due to their gearing not being suitable to making use of the peak power the setup can produce with regard to top speed.

Jack Rickard's 120V Porsche Speedster is being re-geared, and it is expected that it will be able to reach ~110-115 mph; as of 10/14/2009 it could reach 95 mph.



> 2. If the above has to do with electric motor limitation, can't we just slab in a set of transmission to improve it ?, and if this is possible, why big name electric car company hasn't already done it ?


The limitation imposed by the electric motor can be attributed to it overheating from exceeding its maximum continuous current rating. A series wound DC setup that can make 200 horsepower peak may only be able to make 40 horsepower continuous; for most cars, this will mean a max continuous speed limitation of about 90 mph without the motor overheating. A transmission could allow the car to have a higher top speed, but the driver could also potentially overheat the motor. Not all motors are created equal; some AC setups, pound for pound, have about twice the continuous current rating of a DC setup.

Tesla Motors very likely geared their Tesla Roadster for a top speed that will require as much horsepower as its motor can continuously output without overheating. It just so happens that based on the car's weight, CdA, rolling resistance, ect. that the motor/inverter's continuous horsepower rating, on paper, is about the same as would be needed to maintain the car at 120 mph!



> 3. Can an electric motor be designed to excel at certain application than others ? for instance, can we design electric motor that will be suitable for highway cruise, but not so much for city commune and vice versa ?


Yes. It depends on how the motor is wound, and what amount current limitation is imposed by the controller, provided you have a battery pack to provide the desired output.

Certain series DC motors, like the WarP 11" HV or the Kostov, are more suited to making their peak power at the upper end of their max rpm, than say, a WarP 9"; this also depends on whether you have a battery pack with a sufficiently high voltage as well.



> 4. If the above is true, can't we just have 2 separate motors in one electric car and switch between them when driving condition changed ?


You could, but two seperate motors will add greatly to expense. Some racers instead opt to use two of the same motor coupled on a common shaft, and with a single speed gear ratio(usually a differential), they can electronically shift the motors between series and parallel, which greatly increases the flexibility of the car's powerband, and doubles the maximum continuous horsepower over a 1 motor setup. "White Zombie" is an excellent example of a dual motor setup.


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## Bowser330 (Jun 15, 2008)

Speaking of the white zombie...John is now targeting the 10's!

0-60 in 2.7 seconds & 1/4 mile is the 10 sec range & 100mile usable range

Recent Upgrade: He got kokam lithium polymer batteries, brings the race weight down 400lbs! AND can pump out more cranking/peak amps. New Race weight 22XX lbs...


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## toddshotrods (Feb 10, 2009)

Bowser330 said:


> Speaking of the white zombie...John is now targeting the 10's!
> 
> 0-60 in 2.7 seconds & 1/4 mile is the 10 sec range & 100mile usable range
> 
> Recent Upgrade: He got kokam lithium polymer batteries, brings the race weight down 400lbs! AND can pump out more cranking/peak amps.


I need a bib...


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## Bowser330 (Jun 15, 2008)

toddshotrods said:


> I need a bib...


I added race weight of 2,2XX lbs to the previous post...

Besides the batteries there is nothing John has that is so ground breaking, even if his performance and times say otherwise...

He's got twin 8" motors (built) and a single zilla 2K, off the shelf parts...

For people without industry connections the kokams could be subed for A123's or Headways...

The Headway 8AH cell, is 3.2V 8AH (20C) & 300g & 19$ea.

1000 units (100s/10p) = 320V 80AH (1600A @ 20C) 300kg (660lbs) & 19,000$total (not bad)

25.6kwh pack which is about the capacity of John's Kokam pack and hes confident with 100mile+ range at a weight of 22XXlbs.

Meaning with 660lbs of Headways, you would have 1600lbs to work up a frame, motors, controller, body panels, interior, suspension, wheels, glass, etc.

Ive heard that tube frames can be race car strong and still weigh in at around 600lbs, can anyone validate that?


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## toddshotrods (Feb 10, 2009)

Bowser330 said:


> ...Ive heard that tube frames can be race car strong and still weigh in at around 600lbs, can anyone validate that?


That's possible. I can pick my frame up and walk around with it. I would guess it's about 100lbs right now. I have a couple more crossmembers to add, and some boxing, but it should still be around 150lbs. Add another 150 for the cage, 300 for the rear end plus front and rear suspension stuff. That gives me a full roller for 600lbs. My vehicle is very small so increase the weight in proportion to the size and you'll be in the ballpark.


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## JRP3 (Mar 7, 2008)

Bowser330 said:


> He's got twin 8" motors (built) and a single zilla 2K, off the shelf parts...


Jim Husted built siamese 8's aren't exactly off the shelf parts...


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## toddshotrods (Feb 10, 2009)

JRP3 said:


> Jim Husted built siamese 8's aren't exactly off the shelf parts...


He didn't say whose shelf.  



Bowser330 said:


> ...Besides the batteries there is nothing John has that is so ground breaking, even if his performance and times say otherwise...


I want to see one of these monster powertrains in a purpose-built race chassis, that translates the power into maximum forward and/or lateral acceleration - oh wait, that's what I'm supposed to be building!


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## TX_Dj (Jul 25, 2008)

The Toecutter said:


> only the EV never needs to change gears and achieving the best possible acceleration is effortless through its entire speed range.


I'm still not sure who "started" this misconception, but it proliferates.

You're saying that a single-ratio EV is better than a multiple ratio EV.

This isn't true, other than the fact that there is no time lost in changing ratios in the single-ratio EV.

The Tesla had better acceleration with the old 2-speed gearbox than it does with the current 1-speed setup.

Here's why:

Lets build a hypothetical setup, WarP11 motor, 500A Controller, 72v system (same as used to generate its performance graph by netgain): ~140 ft lbs at 1350 RPM with just over 450 amps.
Let's say you have a 5-speed gearbox such as the 2005 Mustang GT:

1 - 3.34
2 - 2.00
3 - 1.32
4 - 1.00
5 - 0.67

Final drive ratio of 3.55 (again, 2005 Mustang GT setup).

Input: 1350 RPM, 140 ft-lbs

1st Gear:
Trans output: 404.1 RPM, 467.6 ft lbs
Axle output: 113.8 RPM, 1659.9 ft lbs

2nd gear:
Trans output: 675 RPM, 280 ft lbs
Axle output: 190.1 RPM, 994 ft lbs

3rd gear:
Trans output: 1022.7 RPM, 184.8 ft lbs
Axle output: 288.0 RPM, 656.0 ft lbs.


4th gear:
Trans output: 1350 RPM, 140 ft lbs
Axle output: 380.2 RPM, 497 ft lbs

5th gear:
Trans output: 2014.9 RPM, 93.8 ft lbs
Axle output: 567.5 RPM, 332.9 ft lbs.

Mathematically speaking, in 100% of cases:
332.9 is not equal to or greater than 497.0
497.0 is not equal to or greater than 656.0
656.0 is not equal to or greater than 994.0
994.0 is not equal to or greater than 1659.9

You will always put more torque to the ground in 1st gear than you will in 4th gear.

Total system gear ratios, and max axle speed for max motor RPM (4700):
1st 11.857:1 ratio, 396.39 max axle RPM
2nd 7.100:1, 661.97 max axle RPM
3rd 4.686:1, 1002.98 max axle RPM
4th 3.550:1, 1323.94 max axle RPM
5th 2.3785:1, 1976.03 max axle RPM

With 235/55R-17 tires (742.1 revs per mile, again, staying with my example of 2005 Mustang GT), this equates to the following max speeds per gear:

1st: 32.04 MPH
2nd: 53.52 MPH
3rd: 81.09 MPH
4th: 107.04 MPH
5th: 159.76 MPH

So, if you gear it with one ratio for best acceleration you have a limited top speed. If you gear it for best top speed, you have limited acceleration. By having selectable ratios, you get the best of both worlds.

Note: I'm not saying that a 72v 500A setup can reach those top speeds, I used the 72v 500A setup example because it matched real-world setup provided by NetGain for the motor in my example.


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## The Toecutter (May 30, 2010)

TX_Dj said:


> I'm still not sure who "started" this misconception, but it proliferates.
> 
> You're saying that a single-ratio EV is better than a multiple ratio EV.
> 
> This isn't true, other than the fact that there is no time lost in changing ratios in the single-ratio EV.


That is not what I am saying. What I am saying is that with no gears to shift, the driver of the EV will be able to achieve the maximum acceleration performance that the car is capable of with its given setup(including gearing), at any time. All he has to do is floor it. Not everyone is an expert at shifting.

I am well aware of the performance advantage of keeping a transmission.


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## DavidDymaxion (Dec 1, 2008)

I love the smell of an AC vs. DC debate in the morning!

I would contend DC's dominance in drag racing is due to cost. If we ever see a cost-is-no-object attack on EV racing, it'll be AC. Just like you see lots of Chevy 350 V8's with carburetors at the drag strip, we'll be seeing DC at the strip for a long time.

I understand and agree with you on the gearing thing. Even given that, though, AC will have a fatter torque curve at the rear wheels. It's just physics . All a series DC motor typically adjusts is total voltage and current on the motor. AC can do that, plus change the slip (kind of like doing brush advance and field weakening on the series DC motor). You simply have more control on the AC motor, hence it's torque curve falls off less fast.

Case in point: John Wayland was running 1200 Amps and 336 Volts of batteries in White Zombie. At that time it had an almost identical 1/4 time to the AC Propulsion Tzero, even though the Tzero was heavier and was running only 600 Amps and capped its top speed! The AC system must have either had a fatter torque curve, and/or better efficiency.


Qer said:


> I've heard this so often now that I'm tempted to call it an urban myth.
> 
> Let's say that we have two systems, one AC and one DC, that both can provide 100 kW peak power and that the AC system does this at 10k RPM while the DC system peaks at 5k RPM. Since power is the result of RPM multiplied with torque this gives that when peak power is reached the DC system might be running at half the RPM but instead gets twice the torque! Now, it's not practical to connect the motors directly to the wheels since a typical car wheel turns at some hundred RPM:s, which will make the motor run rather inefficiently. This means you will need a gear box. Even if you go direct drive, you will need something to gear down the RPM to sane levels, even if you're doing drag racing.
> 
> ...


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## ewdysar (Jun 15, 2010)

DavidDymaxion said:


> I love the smell of an AC vs. DC debate in the morning!
> 
> I would contend DC's dominance in drag racing is due to cost. If we ever see a cost-is-no-object attack on EV racing, it'll be AC. Just like you see lots of Chevy 350 V8's with carburetors at the drag strip, we'll be seeing DC at the strip for a long time....
> 
> Case in point: John Wayland was running 1200 Amps and 336 Volts of batteries in White Zombie. At that time it had an almost identical 1/4 time to the AC Propulsion Tzero, even though the Tzero was heavier and was running only 600 Amps and capped its top speed! The AC system must have either had a fatter torque curve, and/or better efficiency.


Just a little OT rant...

There are still many carbureted small block Chevys, but EFI is slowly taking over. That's part of my next major rebuild of my V8 914. 

15 years ago, AC Propulsion was delivering serious performance, they still seem to have a corner on that "secret sauce". How long is it going to take for that technology to trickle down in an affordable format, something for guys like you and me? Since I'm tired of waiting, I've got a WarP 9 on its way

Stepping off my soapbox,

Eric


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## Bowser330 (Jun 15, 2008)

The Tzero was a custom built tubular racecar, so it had optimum aerodynamics and optimum weight distribution.

Also, a performance AC build is pretty much still a non option for the builder shopping now...

They are still either...
(1) too expensive
(2) too untested/no field data
(3) selling out to the bigs
(4) want to make a deal ($$$) with the bigs... so nothing will be released until the company eventually sells out.

so in my opinion yah people could go on and on about how great AC is, until they are blue in the face, the environment on a consumers side isn't going to change until the technology overcomes its hurdles.


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## DavidDymaxion (Dec 1, 2008)

But White Zombie is optimized for drag racing...

Another Tzero advantage I forgot is its fantastic traction control -- you can hear the tires do a micro-chirp several times a second! Still, I would think a car with drag radials would have the advantage.

Agreed AC is not a practical solution for the average hobbyist. Apparently it is the solution of choice if you have deep pockets (like Tesla, Fisker, GM...).


Bowser330 said:


> The Tzero was a custom built tubular racecar, so it had optimum aerodynamics and optimum weight distribution.
> 
> Also, a performance AC build is pretty much still a non option for the builder shopping now...
> 
> ...


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## Qer (May 7, 2008)

DavidDymaxion said:


> All a series DC motor typically adjusts is total voltage and current on the motor. AC can do that, plus change the slip (kind of like doing brush advance and field weakening on the series DC motor). You simply have more control on the AC motor, hence it's torque curve falls off less fast.


But now you're only comparing AC with series wound motors, not AC versus DC. You're, for example, completely ignoring SepEx. You also ignore the little detail that series wound motors have absolute torque at 0 RPM while AC doesn't and that it's that full torque at a stand still that makes White Zombie so successful despite not having the horse powers of it's competitors.



DavidDymaxion said:


> Another Tzero advantage I forgot is its fantastic traction control -- you can hear the tires do a micro-chirp several times a second!


That's more a question of superior software rather than AC superiority. A fast CPU that can handle for example RPM-data at high speed can handle anti-spin no matter what kind of motor you're using in the end. The "problem" with most DC-controllers are that since the task of controlling the motor is butt-simple, the micro controller used is usually a very simple and slow one. 

An AC-motor demands a more complicated micro controller and (usually, not always) a quadrature encoder with lots of ppt where most DC-controllers use something like 4 ppt or so. 4 ppt isn't enough to handle anti-spin efficiently while the demand for a high resolution encoder (or feedback in some other way) in an AC-controller makes it a breeze (well, ok, at least a lot easier) to handle anti-spin.

There's nothing that says that it can't be done with DC, it just hasn't been done. Yet.



DavidDymaxion said:


> Agreed AC is not a practical solution for the average hobbyist. Apparently it is the solution of choice if you have deep pockets (like Tesla, Fisker, GM...).


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## CroDriver (Jan 8, 2009)

> why is it so difficult for electric car to have high top speed ?


This one is easy:


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## Qer (May 7, 2008)

CroDriver said:


> This one is easy:


Ooo. Nice graph!

It should of course be pointed out that ICE-cars have a similar curve, which can easily be verified with a car that can show the current fuel consumption. Most fossil burners use the least fuel at approximately 70-80 km/h and the faster you go above that, the more fuel you'll burn. It's just that most drivers never reflect over that since gasoline contain almost 10 kWh/liter and a filled up tank therefore contain 0.5-1 MWh where a battery pack isn't even on 1/10 of that.

That's why gasoline cars burn so well!


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## toddshotrods (Feb 10, 2009)

DavidDymaxion said:


> But White Zombie is optimized for drag racing...


Uh, not really. Even with the changes he's making this year, White Zombie is years behind on street-legal drag racing technology. He has a decent setup, but not even in the ballpark of optimum.

Disregarding the weight advantages, you can see this in KillaCycle and Current Eliminator. A HUGE part of the jump from 11s to 7s is the chassis. Somewhere in between that - say 9-sec range - is the potential for an optimized, street-going, EV drag racer. The power is available, but no one has built a vehicle to match it - yet.


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## DavidDymaxion (Dec 1, 2008)

Qer said:


> But now you're only comparing AC with series wound motors, not AC versus DC. You're, for example, completely ignoring SepEx.


Don't forget I'm the guy aiming to do 200 kW with a sepex motor.  I have already done 50 kW with my sepex, only another 150 kW to go.







Despite being a sepex EVer, since you can't buy a high power sepex, I left sepex out of my comments. It would be great if you'd design and sell a high power sepex, I would happily buy a reasonably priced high power sepex solution rather than do my own. Realistically, the market for such a thing would be small and I'll wager series DC will continue to dominate.



Qer said:


> You also ignore the little detail that series wound motors have absolute torque at 0 RPM while AC doesn't and that it's that full torque at a stand still that makes White Zombie so successful despite not having the horse powers of it's competitors.


Nah, not ignoring that. If you can spin the wheels from 0 rpm, any more torque at that point is just wasted. Single gear AC and DC cars like the Tzero and Tesla, and NEDRA racers like Smoke Screen and White Zombie can all spin the wheels at startup, and this "lack" of startup torque for high power AC doesn't seem to be hurting the Tesla's or Tzero's acceleration.

I disagree, I think White Zombie has more horse power than it's competitors! For instance, the video you linked shows White Zombie beating a Tesla. Don't forget, though, the Tesla draws about 600 amps, and the White Zombie draws about 1800 Amps, with similar voltages! Also, the White Zombie is a dedicated drag car, with drag radials and traction mods. I contend that if you lowered White Zombie to 600 battery Amps it would then lose to the Tesla.



Qer said:


> That's more a question of superior software rather than AC superiority. A fast CPU that can handle for example RPM-data at high speed can handle anti-spin no matter what kind of motor you're using in the end. The "problem" with most DC-controllers are that since the task of controlling the motor is butt-simple, the micro controller used is usually a very simple and slow one.
> 
> An AC-motor demands a more complicated micro controller and (usually, not always) a quadrature encoder with lots of ppt where most DC-controllers use something like 4 ppt or so. 4 ppt isn't enough to handle anti-spin efficiently while the demand for a high resolution encoder (or feedback in some other way) in an AC-controller makes it a breeze (well, ok, at least a lot easier) to handle anti-spin.
> 
> There's nothing that says that it can't be done with DC, it just hasn't been done. Yet. ...


Agreed the microprocessor enables awesome traction control and DC could also do that. It is, however, an advantage the AC cars typically have over DC cars -- for $100k to $250k I would hope so.

To summarize, DC is great technology, and this whole debate is over a few percent difference. I like to think of DC like the V8 -- yes you could pay triple for a more "elegant" turbocharged overhead cammed variable valve timing solution, but for my money I'll take the bigger bang for the buck.


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## Bowser330 (Jun 15, 2008)

DavidDymaxion said:


> Don't forget I'm the guy aiming to do 200 kW with a sepex motor.  I have already done 50 kW with my sepex, only another 150 kW to go.
> 
> 
> 
> ...


Please keep us posted on your progress...at what rpm are you planning on being able to extract 200kw from this Sepex motor? 11" ? 13" ?



> Nah, not ignoring that. If you can spin the wheels from 0 rpm, any more torque at that point is just wasted. Single gear AC and DC cars like the Tzero and Tesla, and NEDRA racers like Smoke Screen and White Zombie can all spin the wheels at startup, and this "lack" of startup torque for high power AC doesn't seem to be hurting the Tesla's or Tzero's acceleration.


 oh no but it does hurt their low speed acceleration, thats why the DCs with the extra Amps and extra torque can take the 0-60 crown...however the the acceleration at higher speeds, yes, i agree.




> I disagree, I think White Zombie has more horse power than it's competitors! For instance, the video you linked shows White Zombie beating a Tesla. Don't forget, though, the Tesla draws about 600 amps, and the White Zombie draws about 1800 Amps, with similar voltages! Also, the White Zombie is a dedicated drag car, with drag radials and traction mods. I contend that if you lowered White Zombie to 600 battery Amps it would then lose to the Tesla.


What you are comparing is the sophistication and r&d that went into both of these motors...How OLD is the technology behind forklight DC motors?? not to mention the fact that they were purpose built for speeds of under 20mph...come on man, youre comparing the performance of them to something purpose built for high power & high rpm? Its based on your own comparison of the old V8, think 1990 mustang 5.0 vs 2011 mustang 5.0....you keep going on and on about "600A!"...you know that the 1990's 5.0 motor was not as technologically advanced as the new 2011 ford 5.0...what you are comparing is if the 1990 was using 100 octane race gas, vs 2011 using 91 octane....yah...we get it, millions in R&D and 10 yrs later and you have new better technology...great...



> Agreed the microprocessor enables awesome traction control and DC could also do that. It is, however, an advantage the AC cars typically have over DC cars -- for $100k to $250k I would hope so.


Agreed



> To summarize, DC is great technology, and this whole debate is over a few percent difference. I like to think of DC like the V8 -- yes you could pay triple for a more "elegant" turbocharged overhead cammed variable valve timing solution, but for my money I'll take the bigger bang for the buck


Indeed.


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## Qer (May 7, 2008)

DavidDymaxion said:


> If you can spin the wheels from 0 rpm, any more torque at that point is just wasted.


Apparently the White Zombie, Killacycle etc aren't spinning the wheels but rather shooting off from stop, so it's not wasted. After all the current is converted to torque which becomes a force that accelerates the car, as long as the force doesn't get stronger than the friction between tire and pavement, there's no skidding. So it doesn't really matter when the force overcomes the friction, when it happens, the wheels will spin.

Having a flat torque curve from stand still is an advantage as long as you keep the grip.



DavidDymaxion said:


> Single gear AC and DC cars like the Tzero and Tesla, and NEDRA racers like Smoke Screen and White Zombie can all spin the wheels at startup


The logs I have that comes from street racing runs with cars that runs a Z2K tells a different story. The current jumps from 0 to close to 2000 Amps in less than 10 ms and the motor voltage and (in the cases that's recorded) RPM doesn't show any excessive spinning.

I can show you if you like.



DavidDymaxion said:


> I disagree, I think White Zombie has more horse power than it's competitors!


If you search for White Zombie videos on YouTube you'll see that the Zombie shoots off like mad, getting a serious lead in the beginning, but in many cases when the other car is a serious muscle car it gains on the Zilla through the whole race once it gets moving. It just doesn't gain enough to win. The Zombie has brutal start torque, but there's many other cars that has more horse powers.



DavidDymaxion said:


> Don't forget, though, the Tesla draws about 600 amps, and the White Zombie draws about 1800 Amps, with similar voltages! Also, the White Zombie is a dedicated drag car, with drag radials and traction mods. I contend that if you lowered White Zombie to 600 battery Amps it would then lose to the Tesla.


Indeed. And if you plug most of the cylinders in an ICE dragster my Jeep could probably win against it. That doesn't make my Jeep a better car. 



DavidDymaxion said:


> To summarize, DC is great technology, and this whole debate is over a few percent difference.


No. This so called debate is not about me trying to promote DC over AC, but since there's a tradition, especially online, to see things in a extreme bipolar way, that's what most people read in what I'm trying to say.

My point of view is, and has always been, that you can't compare technologies, you have to compare systems. Right now series wound motors with a Z2K rules the EV street races, not because it's a superior technology (it isn't) but because the series wound motors are good at one thing; full torque at 0 RPM and the Z2K is still the most powerful controller there is when you aim for the quarter mile. They excel at that in a way that as far as I know nothing else is even coming close to beating, AC or DC.

Will it always be like that? Of course not. The Z2K is built on power electronics that's, by today's standard, is getting old so there's definitely room for improvement. However, my guess is that it'll be DC-controllers that will continue to rule the strip for quite some time. In the end what matters is the performance, everything's secondary, and even if it's possible to do an AC system that can beat the White Zombie, it's EASIER to do a stronger DC-system that beats both of them simply because the DC-setup is raw power controlled by a sledgehammer and an anvil. There's nothing elegant about it, the technology is next to ancient (even though the IGBT's of today are some hellish beasts of silicon) but the same amount of silicon needed to dish out somewhere between 0.5-1 MW (which you'll need to beat the Z2K) will be able to handle a lot more in a traditional DC-controller.

Will it always be like this? Good question. As the price for silicon drops, the price difference between AC and DC will probably shrink and with that AC might, finally, kill the DC-market even for DIY'ers, although I'm not holding my breath. So why do the big ones go for AC if it's so expensive and complicated? Good question. My guess is that a water cooled motor is easier to make trouble free (no foreign objects that gets into the motor through the ventilation, less risk the motor gets destroyed by high currents at low RPM etc) combined with the fact it can regen without extra hardware. That's probably also the reason Renault went with SepEx in the old Clio (the SepEx is fairly easy to use for regen as well and since they bolted a blower on it it got sufficient cooling even at low RPM's). After all, if you want to build an EV that behaves in a way that an ordinary driver recognize, regen is probably a must.


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## Tesseract (Sep 27, 2008)

Qer said:


> ...So why do the big ones go for AC if it's so expensive and complicated? Good question.....


Two big reasons:

1. Much easier to comply with EMC regulations (no brushes producing conductive dust so the motor can be sealed).

2. More benign failure mode (a shorted switch results in a strong braking effect in the rotor, rather than runaway acceleration).

***

When it comes to controllers, the comparison between AC and DC is very simple.... and there's no comparison. Sorry, that's just the facts. I really don't care one way or the other. I am agnostic about this whole stupid debate, but it really drives me bonkers to see the same myths trotted out over and over again. Hell, you'd think AC motors could cure cancer they are so loved! Anyway, let's compare what two controllers - one DC, the other AC - can do with the same amount of silicon (namely, three IGBTs rated for 500Arms) and a 340VDC battery pack:

The DC controller can drive it's IGBTs all the way from 0% to 100% so the maximum output (assuming no sag) would be 340V x 3 x 500A or 510kW.

The AC inverter can't ever turn its IGBTs on 100% because it has to always modulate them to create a sine wave current in each phase. Thus the maximum output voltage is 340V / 1.414 (2^0.5), or the familar 240Vrms. Furthermore, each phase can't contribute equally to the production of torque, so instead of 3x the phase current the actual multiplier is 1.732x (3^0.5). When you string it all together in an equation you get a maximum power output of: Vbatt x Iphase x (1.732/1.414), or ~208kW.

You will always be able to make a more powerful DC controller with a given amount of silicon. Simple as that.


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## JRP3 (Mar 7, 2008)

Nice explanation. How do PM DC motors fit into the picture?


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## ewdysar (Jun 15, 2010)

Qer said:


> ...Will it always be like this? Good question. As the price for silicon drops, the price difference between AC and DC will probably shrink and with that AC might, finally, kill the DC-market even for DIY'ers, although I'm not holding my breath. So why do the big ones go for AC if it's so expensive and complicated? Good question. My guess is that a water cooled motor is easier to make trouble free (no foreign objects that gets into the motor through the ventilation, less risk the motor gets destroyed by high currents at low RPM etc) combined with the fact it can regen without extra hardware. That's probably also the reason Renault went with SepEx in the old Clio (the SepEx is fairly easy to use for regen as well and since they bolted a blower on it it got sufficient cooling even at low RPM's). After all, if you want to build an EV that behaves in a way that an ordinary driver recognize, regen is probably a must.


And that is what I was hoping for after dropping out of the scene for 15 years, but apparently, things haven't changed that much. There are more AC systems available for DIYers, but their performance isn't what I'm looking for. I figured that after Impacts (or EV1s) and more recently Teslas, there would be more higher tech options at our level. Batteries are better, for a price, but at least they're out there. New DC controllers are pretty cool compared to the old Curtis standards. But most of this seems incremental, not revolutionary. Pirating parts from old forklifts still seems to hold on to a decent market share of this industry. 

I'm finally going to build another DC car, to exploit the Lithium advantage and more controller than what was available in the '90's, then maybe back to sleep for another decade or so. Maybe this time, the rest of the world will catch up to us visionaries... 

Eric


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## toddshotrods (Feb 10, 2009)

ewdysar said:


> And that is what I was hoping for after dropping out of the scene for 15 years, but apparently, things haven't changed that much. There are more AC systems available for DIYers, but their performance isn't what I'm looking for. I figured that after Impacts (or EV1s) and more recently Teslas, there would be more higher tech options at our level. Batteries are better, for a price, but at least they're out there. New DC controllers are pretty cool compared to the old Curtis standards. But most of this seems incremental, not revolutionary. Pirating parts from old forklifts still seems to hold on to a decent market share of this industry.
> 
> I'm finally going to build another DC car, to exploit the Lithium advantage and more controller than what was available in the '90's, then maybe back to sleep for another decade or so. Maybe this time, the rest of the world will catch up to us visionaries...
> 
> Eric


Dude you haven't been paying attention to how life works. Society follows the basic pattern of life. Evolution and change are incredibly slow processes. This whole sustainable, renewable, energy thing being pushed now is decades from reality. It just takes a major initial push to even get the ball rolling, then years and years of subtle refinements. For comparison, study the evolution of the ICE after it was universally adopted as the standard. Even with racing fueling development, _major_ changes didn't occur until emissions laws forced electronic control. That was many decades after it was chosen...

The problem with AC for anyone but manufacturers (for the reasons given above) is there is no real need. It's not going to do anything that much better than those old forklift motors, to justify the cost of adopting it. I wanted SepEx for regen, but for the cost and complexity I can just step on the brake pedal and adjust my driving style.

Considering the fact that the biggest need of a DIY commuter is to get moving, the torque of a DC motor isn't so bad. Considering the fact that they're rarely ever going to need excessive speed there's no issue with the lack of top end rpm.

For a racer (like me) it is far more practical to compensate for the DC motor's weaknesses than try to adopt AC or SepEx. Proper gearing and brakes will elminate those in short order.

I guess what I am saying is you better eat up, it could be a long hibernation. I do believe that _eventually_ AC will rule the day, but that eventually is a long way out. This whole movement is. Oil is still flowing too freely (too much so in the Gulf), and too inexpensively.


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## major (Apr 4, 2008)

Tesseract said:


> You will always be able to make a more powerful DC controller with a given amount of silicon. Simple as that.


Hi there Tesseract,

Yeah, there are simple ways of looking at things. And simple analysis often omits some things which should be considered. I think it is and always has been a given that an equal power AC drive will have more silicon that its DC counterpart. 

I contend it is unfair to compare the two with given amounts of silicon, because the silicon inside the AC and DC controllers performs different functions. You might say that a large percentage of the silicon in the AC controller is devoted to commutation (the switching of the direction of current in the motor). Whereas the DC controller cheats by leaving commutation to the mechanism inside the motor. 

I think that big rotating mass of copper and mica, the carbon brushes, springs, holders, insulator plate, connectors and housing extension are likely worth the price of 3 or 4 of your IGBTs 

Regards,

major


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## Qer (May 7, 2008)

ewdysar said:


> New DC controllers are pretty cool compared to the old Curtis standards. But most of this seems incremental, not revolutionary. Pirating parts from old forklifts still seems to hold on to a decent market share of this industry.





toddshotrods said:


> The problem with AC for anyone but manufacturers (for the reasons given above) is there is no real need. It's not going to do anything that much better than those old forklift motors, to justify the cost of adopting it.





major said:


> I think that big rotating mass of copper and mica, the carbon brushes, springs, holders, insulator plate, connectors and housing extension are likely worth the price of 3 or 4 of your IGBTs


And I think that within these three quotes lies the truth. The AC systems give too little benefit for the average DIY:er to be worth the cost and even if I agree with Major that using brushes is "cheating" it doesn't change a thing when it doesn't mean the AC-motor compensates for the more expensive controller by being cheaper than the DC-motor.

As long as the AC-systems are less !/$ they won't rule the DIY:ers because the average DIY:er is on a tight budget. For example, I don't know how many times I've read posts like "I'd love a Zilla or a Soliton, but...". Those guys would simply never pony up for an AC-system (probably because then they'd have to sleep on the couch for a month, I know I'd end up risking that...  ) and since the DIY-market is rather small, we therefore probably won't see many AC-systems. At least not until there's an AC-motor with a decent !/$-ratio.

Thus, incremental development of DC-systems it is...


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## Tesseract (Sep 27, 2008)

major said:


> I contend it is unfair to compare the two with given amounts of silicon, because the silicon inside the AC and DC controllers performs different functions. You might say that a large percentage of the silicon in the AC controller is devoted to commutation (the switching of the direction of current in the motor). Whereas the DC controller cheats by leaving commutation to the mechanism inside the motor.
> 
> I think that big rotating mass of copper and mica, the carbon brushes, springs, holders, insulator plate, connectors and housing extension are likely worth the price of 3 or 4 of your IGBTs


You are absolutely correct... at least when it comes to industrial motors. A casual survey of the Baldor catalog (chosen only because it posts prices) shows that a DC motor of any given size and ventilation style will cost 5-10x more than its equivalent AC induction motor. 

But... and there's always a but.... The DC motors we most commonly use - e.g., NetGain, ADC, Kostov - are on par in cost, or only modestly more expensive, than their industrial AC equivalents (and don't even try to compare them to their EV AC equivalents).

In general purpose commuting applications the continuous power rating of the motor is most important (e.g. - driving on the highway for 30-50 miles). Here the controller can be sized closer to that of the motor's S2:60 rating (e.g. - a 50kW controller and a 20kW motor).

In racing applications, though, the S2:60 rating of the motor is very nearly irrelevant. You might drive two 20kW motors (Siamese WarP 8's) with a "640kW peak" controller. When you get to such an extremely high controller to motor power ratio the difference in the price of the motor is, like their S2:60 ratings, nearly irrelevant. 

So, my analysis might be overly simplistic, but it still seems to apply. No cheating required


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## CroDriver (Jan 8, 2009)

I wouldn't say that AC is more expensive for OEMs than DC. AFAIK BMW payed $11k for AC-Propulsions's 200kW Motor-Inverter-Charger-BMS system for the E-Mini. That's not bad for such a system. We DIY-ers would pay almost the same for a new 1000 Amp controller, 11" motor, charger, BMS, contactors, throttle pad etc.

And they built "only" 500 of them. The price would probably drop even more with some more serious numbers of units for a player like BMW. 

I don't see a single reason why OEMs would choose DC over AC, and that's why no one does. But I see thousands of reasons why we should choose DC ($$$) 

I haven't seen noone who's willing to pay the $38k for the UQM system. And there was also a new AC system from another US company with high performance AC systems at a more reasonable price but I can't remember the name... The motors looked like Siemens (the motor housing wasn't round, more like a brick..). Can someone remember the name?


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## JRP3 (Mar 7, 2008)

Calmotors, which I think were actually Parker-Hanifin units. I'm not sure they are actually selling anything. As for UQM, they simply do not want to sell to individuals, hence the insane price. I'll bet OEM's aren't paying even half that.


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## JRP3 (Mar 7, 2008)

Qer said:


> As long as the AC-systems are less !/$ they won't rule the DIY:ers because the average DIY:er is on a tight budget. For example, I don't know how many times I've read posts like "I'd love a Zilla or a Soliton, but...". Those guys would simply never pony up for an AC-system (probably because then they'd have to sleep on the couch for a month, I know I'd end up risking that...  ) and since the DIY-market is rather small, we therefore probably won't see many AC-systems. At least not until there's an AC-motor with a decent !/$-ratio.


For a moderate power low voltage system I'd say the AC31 and AC50 are just that. Yes they are around $4K but you have to look at the total package. You also get instrumentation that gives you current, voltage, motor and controller temp, and RPM's. Add all that to your DC system and the price gets a lot closer. Higher voltage, yeah you're out of luck. I'd love a Zilla or a Soliton, but....they aren't AC


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## tomofreno (Mar 3, 2009)

Here's one reason I like AC (lifted from my SwiftE thread): 
Drove up to Mt. Rose summit today. About 4594 ft (~1400 m) elevation gain over 19.3 miles (~32 km) from the bottom on S. Virginia St., so about 4.5% grade average (considerably steeper in parts). Used 65.1 Ah going up, at about 40 to 45 mph. _No use of mechanical brakes on the way down, just electric braking, except near the bottom where I stopped for a traffic light_. It is not at all unusual to smell burning brakes from cars in front of you going down this hill, as there is repeated braking on steeper parts and at hairpin switchbacks. 

It was a joy controlling speed on the way down using only the throttle pedal. And regen for 19 miles! Like Cro said, the cost advantage of DC is much smaller for OEMs. Yeah, I know, "how many people drive up and down mountains like this regularly?" Not this big, but plenty people in the western U.S. regularly drive up and down 1000 - 2000 ft elevation gains when commuting. And this is one of the main routes from Reno to Lake Tahoe, so it has a steady stream of traffic each day. An OEM has to design a car for all uses and areas, cold/hot weather, flat/hills, etc.

There are lots of happy ev'ers driving DC powered vehicles. Just wanted to point out an advantage of AC.


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## ewdysar (Jun 15, 2010)

CroDriver said:


> I wouldn't say that AC is more expensive for OEMs than DC. AFAIK BMW payed $11k for AC-Propulsions's 200kW Motor-Inverter-Charger-BMS system for the E-Mini. That's not bad for such a system. We DIY-ers would pay almost the same for a new 1000 Amp controller, 11" motor, charger, BMS, contactors, throttle pad etc.
> 
> And they built "only" 500 of them. The price would probably drop even more with some more serious numbers of units for a player like BMW.


I would buy an AC Propulsion drive system for $11k. Their current offering of converting a Scion xB for $55k, making the eBox a $70k car, is just too rich for my accounts. I haven't seen anybody making these drives available to individuals.

I heard early reports that the eMinis were not great cars, fun to drive but with fairly short range. The eBox seems to hit a better balance with "... accelerates to 60 mph in 7 seconds, reaches a top speed of 95 mph and will go between 120 and 150 miles on a charge." But it's still too much money...

Eric


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## major (Apr 4, 2008)

Tesseract said:


> You are absolutely correct... at least when it comes to industrial motors. A casual survey of the Baldor catalog (chosen only because it posts prices) shows that a DC motor of any given size and ventilation style will cost 5-10x more than its equivalent AC induction motor.


So what you have discovered is that if AC and DC motors suitable for EVs were manufactured on equivalent basis (such as industrial motors), the AC motor would cost 5 to 10 times less  That leaves a lot of margin to buy that extra silicon.


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## Tesseract (Sep 27, 2008)

major said:


> So what you have discovered is that if AC and DC motors suitable for EVs were manufactured on equivalent basis (such as industrial motors), the AC motor would cost 5 to 10 times less  That leaves a lot of margin to buy that extra silicon.


No, that's not quite it... A 20hp continuous rated AC induction motor from Baldor might cost $1500. A similarly continuous rated 9" motor from NetGain, Kostov or ADC might cost anywhere from $1300 to $1800. There is no price difference between the DC motors we use and industrial AC motors, in other words. There is a HUGE premium in cost for industrial DC motors, though it is not clear to me why that is the case.


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## major (Apr 4, 2008)

Tesseract said:


> No, that's not quite it... A 20hp continuous rated AC induction motor from Baldor might cost $1500. A similarly continuous rated 9" motor from NetGain, Kostov or ADC might cost anywhere from $1300 to $1800. There is no price difference between the DC motors we use and industrial AC motors, in other words. There is a HUGE premium in cost for industrial DC motors, though it is not clear to me why that is the case.


Apples and oranges 

Let me elaborate. You compare the EV DC motor to the industrial AC motor and find cost about equal. You compare the AC industrial motor to the DC industrial motor and find the DC is 5x the cost of the AC. Why then does the logic breakdown when the EV AC motor would have the manufacturing basis of the DC EV motor? The EV AC motor should cost 5 times less than the EV DC motor all things being equal.

Your problem is comparing a DIY EV DC motor to any industrial motor. Why does an industrial DC motor cost 5 to 10x the EV DC motor? Apples and oranges


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## ThWongs (Sep 4, 2010)

Very interesting and educational topic! I'm learning a lot from surfing around. 

I was also surfing around the www this evening and found this...

http://www.nissan.co.uk/vehicles/electricvehicles/leaf.htm#vehicles/electricvehicles/leaf

I want one!


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## zeroemission (Sep 14, 2010)

kudos to dymaxion! graphs like that are (almost) exactly the kind of info i've been banging my head against the wall in vain trying to find!

you wouldn't happen to have a basic X mass by Y watts (or vice versus) at 55mph graph up your sleeve would you? i'd buy THAT for a dollar!


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## DavidDymaxion (Dec 1, 2008)

Glad you liked the plots. Attached is one for Power vs. Weight. I assumed a 2% rolling resistance, pretty high, you can do better with low rolling resistance tires. Note for a steady 55 mph, weight doesn't make much difference -- however accelerating or going up hill is when the extra weight will get you. The other caveat is this is for a fairly aerodynamically clean car.


zeroemission said:


> kudos to dymaxion! graphs like that are (almost) exactly the kind of info i've been banging my head against the wall in vain trying to find!
> 
> you wouldn't happen to have a basic X mass by Y watts (or vice versus) at 55mph graph up your sleeve would you? i'd buy THAT for a dollar!


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## motor guy (Dec 17, 2008)

hello all
i have been reading the thread and maybe i am missing something. are you saying over 100mph or higher?
a week ago i told you all that our s10 went 95.5 miles on a single charge. this was done on a average of 45 mph.
we went out and did a run to see how fast we could get without getting in trouble, we managed to get 97 mph before traffic became an issue.and the truck was still pulling.
we have also noticed that adding weight, (when we make deliveries, by adding up to 800 lbs of motors), doesnt make that much difference in its performance.
i feel that the biggest reason the truck works as good as it does is beacuse, it has a good controller, a working 5 speed trans,no subsitute for torque multiplication.
yesterday, carl clark with the electric car co. came to our shop, he got to witness and video how the truck performs, he said he was going to post the video.
when building an vehicle, race related, ev, custom tube chassis there are certain values that need to be checked, wheel percentages, roll centers, weight bias, and so on, these items will affect the performance of the vehicle. removing weight and readding weight, in different areas will greatly affect overall handling and driveability.
thanks kevin


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## DavidDymaxion (Dec 1, 2008)

Awesome! 97 mph is good, especially for a truck. 95.5 miles is very good range. I'm looking forward to watching the video. I'm local to Carl and hoping to see him build a truck like yours.

The highest verified speed for a conversion (that I know about) is 132 mph, set by Silent Thunder on the Salt Flats. It was a Ford Taurus with four motors and 336V of lead acid. The Tesla goes 125 mph, but is limited, it likely could go faster with taller gearing. Hopefully I'll be able to bump that number up a bit with my conversion with more batteries (just running 48V at the moment). I'm about to start testing a couple of High Power batteries to see if they can dish out enough power.

Have you thought about putting narrow wheels, mooneyes wheel covers, fender skirts, grill cover, a belly pan, and a bed cover on the truck? You might raise the top speed by 10 or 15 mph.


motor guy said:


> hello all
> i have been reading the thread and maybe i am missing something. are you saying over 100mph or higher?
> a week ago i told you all that our s10 went 95.5 miles on a single charge. this was done on a average of 45 mph.
> we went out and did a run to see how fast we could get without getting in trouble, we managed to get 97 mph before traffic became an issue.and the truck was still pulling.
> ...


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## motor guy (Dec 17, 2008)

thanks for the compelment.
we are using batteries from carl. 48 cells at 200 amphr.
some early morning we are going to make another speed run. before the world wakes up and the local police is still at the coffee shop. and we will turn the controller up to full power. we have the soliton1 set at 500 amps. to keep from tearing things up.
carl is a neat guy, full of BS, but funny guy.carl asked if next spring if we would consider taking our truck to the salt flats. something to ponder on.
i built drag cars and did lots of chassis work, so that is were all all the weight values come from. i honestly feel that the truck cold run about 110 to 115mph. call me crazy. or just see/or ask what carl thinks.
i dont spend alot of time worring about lots of electrical formulas, because just like in racing v-8 engines you have torque curves, so does electric motors. and having knowledge with both is a benefit. what most folks forget is that they are designing there vehicle around gear ratios the were designed around a torque cure between 1200-2000 rpm. 
i will leave that for now.
thanks kevin
topekaelectricmotor.com


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## motor guy (Dec 17, 2008)

sorry but my typing and proof reading leave something to be desired.
i will work on it.

thanks again kevin


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## DavidDymaxion (Dec 1, 2008)

I like your attitude and willingness to give your product a speed run!

I would second going to the Salt Flats, it is great fun. I think that Carl should build a truck and you two should run. I'll be running my Porsche again. I still need to post a web page about this year's Salt Flats adventures.


motor guy said:


> thanks for the compelment.
> we are using batteries from carl. 48 cells at 200 amphr.
> some early morning we are going to make another speed run. before the world wakes up and the local police is still at the coffee shop. and we will turn the controller up to full power. we have the soliton1 set at 500 amps. to keep from tearing things up.
> carl is a neat guy, full of BS, but funny guy.carl asked if next spring if we would consider taking our truck to the salt flats. something to ponder on.
> ...


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## The Toecutter (May 30, 2010)

I am interested in the prospect of taking mine to the Salt Flats as well, once it is finished that is... How to get it there might be an issue that poses some problems!

Beating the unofficial record set by Silent Thunder, is in theory, doable for less than $10,000. I might have my conversion finished for less than $7,000 when all is said and done; time will tell whether it performs according to simulation. If it ever matches or beats Silent Thunder's record, it will moreso be the byproduct of designing for long range, than performance.


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## DIYguy (Sep 18, 2008)

DavidDymaxion said:


> Awesome! 97 mph is good, especially for a truck. 95.5 miles is very good range. I'm looking forward to watching the video. I'm local to Carl and hoping to see him build a truck like yours.


 Nice. I've had my Mazda B4000 over 100mph. It was still building quite strong. I don't know how fast it will top out at. it is 192 volt nominal AGM batteries... with the Soliton also. It has a 9 inch GE motor advanced 13 degrees.


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## DavidDymaxion (Dec 1, 2008)

DIYguy: To quote the old Ford commercial: "Fun Truckin'!" Hmm... <scribbles furiously> if a truck can go 97 on about 160V... and 100+ on 192 V... and my Porsche has 1/2 the aero drag... and I go up to 240V... that's about 137 mph... I'd take that! Now just that detail of making it reality...

ToeCutter: Rent a U-Haul truck and trailer to bring your car to the Salt Flats. Another trick is to buy a truck, and then sell it after the event is done.


DIYguy said:


> Nice. I've had my Mazda B4000 over 100mph. It was still building quite strong. I don't know how fast it will top out at. it is 192 volt nominal AGM batteries... with the Soliton also. It has a 9 inch GE motor advanced 13 degrees.


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## Alexander_B (Oct 19, 2010)

neat  and no, beating records doesn't have to be over $10k, you don't need awesome range, you only need batteries with a low internal resistance, and a low drag car with a big motor. in fact, with less battery (less weight) it should only be easier. a 3 kwh pack of A123's is about 5k$, and can deliver 150 kilowatts for 1.5 minute (until empty), and recharger for the next run in about 15 minutes.. the car itsself should be the most low and aero little sportscar you can find, some pretty good ones were made in brittain, to name something, but other cars should work as well. then you only need a big 11" or so motor, and a suitable controller (with contactor override for extra power @ cheap, and pwm controller for the initial acceleration and/or slower driving) and you're set to break records or gearboxes.

- donor car $500
- battery $4500-5000
- motor $1500 unless you find a nice forklift motor.
- controller $1500? perhaps less, perhaps more, depends on what you buy/can afford.
- wiring, connectors, contactors <$500-1000
- charger $200
- other misc stuff: $300-800 left!


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## Jason Lattimer (Dec 27, 2008)

I think the old saying my dad used to tell me about musclecars when I was a kid still rings true.

"How fast do you want to go? How much money do you want to spend?"

Besides, unless you live in Germany, why do you need a car that can run triple digit speeds? You can't go that fast on any road, and I don't even know of a race track, other than a drag strip you can do it. I think it is purely for bragging rights.


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## DavidDymaxion (Dec 1, 2008)

I have hit almost 130 mph at a road racing track with a 300 hp daily driver. Some of my friends have hit 145+. Also, don't forget the Salt Flats, cars have gone 400+ mph there, plus an electric has exceeded 300 mph.

I think high speed exploration actually benefits electric cars. High speed = good range. For instance, Bill Dube estimated the Killajoule land speed racer could go about 500 miles, on a 200 pound battery pack! http://www.facebook.com/killacycle . Land speed racers optimize for aerodynamics and run narrow tires. If you want to find an efficient car, or good aero mods, look to the land speed racers.

For practical reasons, you need enough power to go maybe 40 mph faster than cruise speed, to have adequate margin to fight headwinds and climb hills.

Finally, don't forget the marketing aspect. I was amazed how few people knew about the EV-1, or that Chevy and Ford had electric trucks, or about the Honda EV+, or about the RAV4EV. In contrast, I'm amazed how many people know about the Tesla -- speed sells!


Jason Lattimer said:


> I think the old saying my dad used to tell me about musclecars when I was a kid still rings true.
> 
> "How fast do you want to go? How much money do you want to spend?"
> 
> Besides, unless you live in Germany, why do you need a car that can run triple digit speeds? You can't go that fast on any road, and I don't even know of a race track, other than a drag strip you can do it. I think it is purely for bragging rights.


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