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Discussion Starter · #1 ·
I have been doing some research for about two months now just trying to get a ground of where to start a new EV and could use some help. I am going to make an EV from scratch. I am expecting this project to take about 3 to 5 years or so, thus I am in no rush at all. I still have tons to learn about a variety of things for this undertaking and I am pretty optimistic about it. I have been thinking about a good place to start, and after much deliberation I have decided to start with a motor and plan on from there. I definitely want to go with an AC motor. My budget that I plan on spending for the whole car is about 50,000, give or take 20,000 if need be for everything that i want in it. So back to starting with the motor I would like something around 250-300kw. Anyone have any suggestions? Again, I am just starting out, thanks for any help!

-Jake
 

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Discussion Starter · #3 ·
Well I have thought about a conversion, but it won't have everything that I want in it. That's when I decided to go from scratch, that way I can control every aspect of the car.

Thanks for the suggestion though, I revisited the thought but I think it would be rather difficult to place the motor in the back of the car.
 

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What car or truck are you planning to convert? Are you looking for an 'easy' conversion?

What type of range are you looking for?

And for that kind of money, you might want to look into an EV from a big car company.
 

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Hi Pirate

$50,000 will build you an awesome car
BUT it won't build you a saloon car as good as a Tesla S

It can build a car to meet specific needs (high performance, looks....) better than something like the Tesla - but not overall

There is a reason it has cost millions to develop the Tesla

Anyway - the first thing you need to do is to determine
What are your specific needs??

Then we may be able to help you with ideas/suggestions
 

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With the budget you have and the performance you want, I think your best AC option would be to get a motor and controller from Bob Simpson. His motors are very well built, with liquid cooling and even with cooling of the rotor. So it has a very high continuous power rating (much higher than any DC motor which are very good for peak power but bad for continuous since it is difficult to do liquid cooling). His controllers are made by Rinehart, which for my money is the best AC controller available to DIY. It won't be cheap, but it will be a monster. He has just one that sounds like it is just what you want for 37k. You'll need probably a 30kwh pack to run it. That would put you back another 15k if you bought it today...probably cheaper when you are ready for that part. Another 10k for a donor worthy of these components, and another 5-10k for charger, dc-dc and odds and ends, and you will be pushing the upper limits of your budget. But if you do a good job it would be worth way more.

Interested to see what you have in mind for a donor. Me, I'd see if I could cram it in an Audi TT Quattro...that kind of power would like 4wd. I don't have your budget though :)

You'll get plenty of pressure on here to do it cheaper. You could have similar peak power for 20k less if you went DC. But I say if you have the money, go for the gold.
 

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Since you say you want to build from scratch, and not convert an ICE car, you may want to read the following report that I found for a small EV.
http://www.ohio.edu/mechanical/design/projects/team2_design_report_final.pdf

You can scale up to meet your desires. 250-300 kW is a lot of power for an electric motor, and is equivalent to a 1000 HP (peak) ICE. So that is the realm of serious racing cars and dragsters, or heavy trucks and buses.

If you are really just starting out with little experience in electrical and mechanical engineering, I would suggest first "cutting your teeth" on a small test project, which could be a bike or a tractor or golf cart. You should be able to get something up and running in a few months and the experience will carry over to your main project. You can afford to make mistakes and start over a few times if you are building a $300 bike or a $600 tractor, but for a monster like you are planning, mistakes can be costly and quite dangerous! :eek:

Good luck, have fun, learn much, and be safe! :)
 

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With the budget you have and the performance you want, I think your best AC option would be to get a motor and controller from Bob Simpson. His motors are very well built, with liquid cooling and even with cooling of the rotor. So it has a very high continuous power rating (much higher than any DC motor which are very good for peak power but bad for continuous since it is difficult to do liquid cooling). His controllers are made by Rinehart, which for my money is the best AC controller available to DIY. It won't be cheap, but it will be a monster. He has just one that sounds like it is just what you want for 37k. You'll need probably a 30kwh pack to run it. That would put you back another 15k if you bought it today...probably cheaper when you are ready for that part. Another 10k for a donor worthy of these components, and another 5-10k for charger, dc-dc and odds and ends, and you will be pushing the upper limits of your budget. But if you do a good job it would be worth way more.

Interested to see what you have in mind for a donor. Me, I'd see if I could cram it in an Audi TT Quattro...that kind of power would like 4wd. I don't have your budget though :)

You'll get plenty of pressure on here to do it cheaper. You could have similar peak power for 20k less if you went DC. But I say if you have the money, go for the gold.
A link might be nice...
 

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Discussion Starter · #10 ·
Pstechpaul,

250 kw is about 335 hp if I am not mistaken, Which after a little more research into motors may be somewhat more than I need.

Duncan,

I think you just about have my idea pegged! I'm not exactly trying to build a Tesla, but something similar to it where i have all the control over the design. I have been thinking about my requirements and two things come to mind. Range being the first. I live in Austin, TX and would like to have the ability to travel to some of the major cities on a single charge. That being said 250 to 300 miles would be ideal. Secondly i would like a good deal of power to be able to get up and go. I do a considerable amount of interstate driving, so being able to get up and around people would be nice if needed. I assume that the 250 kw that i stated would be peak power, only used when say going uphill or to pass someone. I will have to figure out specific figures later, but are electric motors rated by their peak power? I read the amount of kw produced depends on your controller and if your motor and batteries can handle the load. I think i need to buy a book and do more research on this matter as I feel so lost! Any suggestions?

-Jake
 

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I think you just about have my idea pegged! I'm not exactly trying to build a Tesla, but something similar to it where i have all the control over the design. I have been thinking about my requirements and two things come to mind. Range being the first. I live in Austin, TX and would like to have the ability to travel to some of the major cities on a single charge. That being said 250 to 300 miles would be ideal. Secondly i would like a good deal of power to be able to get up and go. I do a considerable amount of interstate driving, so being able to get up and around people would be nice if needed. I assume that the 250 kw that i stated would be peak power, only used when say going uphill or to pass someone. I will have to figure out specific figures later, but are electric motors rated by their peak power? I read the amount of kw produced depends on your controller and if your motor and batteries can handle the load. I think i need to buy a book and do more research on this matter as I feel so lost! Any suggestions?

-Jake
There's certainly nothing wrong with buying books and doing research, but you will probably learn more from here than from any given book.

As far as power requirements go, you need a lot less than you might think to cruise around at interstate speeds. But I'm guessing you don't want a weenie car that's barely powerful enough.
Electric motors are in fact measured in peak power as well as continuous power rating. But you have to be careful comparing electric power ratings with ICE power ratings. With an ICE, the peak power is a point on a narrow power band that falls off rapidly to each side. On an electric motor, you have a wide flat power band. The maximum power rating is a point at the high side of the flat part (since power is torque times speed) but that same torque extends all the way back to zero RPM instead of falling off. So you get a lot more out of an electric motor than you do out of an ICE for a given power rating. With an electric motor, when we talk about peak power, that's referring to how long of a time the motor can output that power before it has to pull back due to temperature issues. For a brushed DC motor, the difference between peak and continuous ratings is huge. A DC motor can briefly handle mindblowingly high amounts of power for brief periods of time, as long as you have a controller that can throw the current at it. But, since they are pretty much always air cooled (the heat is generated primarily in the rotor, which is hard to liquid cool) the continous ratings are actually quite low. With a liquid cooled AC motor, the peak values tend to be lower while the continuous values are much higher. With an undersized DC motor, you can run into temperature problems with normal driving. With a liquid cooled AC motor, a motor that is powerful enough to accelerate you will probably have enough power to drive around at decent speeds. The motors you will want for quickness will much more continuous power than you ever need.

For the range you are wanting, that's going to cost a good 30 grand, so that will eat up a lot of your budget. On the other hand you probably don't really need as much power as you initially said. I still would say go with evdrive.com...but if you go down to a single controller option, you can get a 180kW peak system for under 20 grand. It won't be as powerful as a Tesla but it will be very quick and fast.

One thing that going overboard on power gets you is the opportunity to go single speed. I don't know if that is important to you or not, but if you went for the ~180kW peak option, I would probably retain multiple gears.

What do you have in mind for a "glider" or donor car? It kind of sounds like you want to make your own. While that is not impossible, it does suddenly make the project at least an order of magnitude more difficult and expensive. Keep in mind that even Tesla didn't make their own glider their first go around. There are a lot great donor car options out there...I'm guessing you might find one that suits you well. Do consider using one with all wheel drive. That way you won't just use all that power to convert your tires into smoke.

Sounds like a really fun project! I wish you lived in Portland so I could help you with it. Ah...maybe some day I'll have a decent budget available :)
 

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If you're wanting to build the car as well, consider buying a kit. There are some very interesting kits available from Factory 5 Racing (famous for the AC cobra kit). One of their new ones is called project 818, for 818 kg. It's a mid engine layout that starts with a Subaru WRX for the majority of it's parts. If I remember correctly, they were also working on a similar kit based on the VW Jetta, for a diesel mid-engine 2 seat sports car. Either way, there's a great base for a mid-engine EV. :cool:

Also, it helps a lot to consider the base weight and especially the aerodynamic drag of the vehicle. If you're spending the majority of your time at highway speeds, a low Cd will be a big help for range.

There's a nice feed back-loop: Lower weight/less drag > fewer batteries needed > lower weight....
 

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Hi Pirate
Have you built a car before?
The reason I ask is because it is the little jobs that eat the time and money
If you have a body/chassis built with motor and all running gear in place - you are about 7% of the way there!
The other 93% is all little finicky jobs

Your options:
Conversion
Kit car
Scratchbuilt - existing design
Scratchbuilt - your design

Each step is a lot more work than the previous one

If you have a budget of $50,000 and range requirement of 300 miles
your battery will cost ~ $30,000
Leaving $20,000 for everything else

How often do you drive for 300 miles? - is it worth hiring a car for those journeys?
300 miles is getting awful close to the edge of the envelope with today's technology

If you want your own design - what do you NEED?
What can you live without?

My car is real basic
- no doors, no windows, no windscreen, no heater, no padding, no interior trim
It is great fun - but no good for a long drive
And because it is no good for a long drive it does not need a long range

http://www.diyelectriccar.com/forum...-dubious-device-44370p2.html?highlight=duncan
 

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Discussion Starter · #14 ·
Sorry I've been away for a while with work. So Duncan this will be my first car. My father has experience building cars, when I was little he was always doing something or another, restoring cars in his spare time. I realize this will be a tremendous amount of work, but the challenge is what makes me want to do this even more. That being said, the budget can be flexable, as I will have plenty of time to buy the parts needed. I have been doing a little research on batteries and the prices of lithium-ion are dropping yearly so I am not too concerned about this. Currently I drive the 300 mile trip up to see my family in East Texas maybe once a month, but when this car is done I am planning on about two trips a month, maybe a few more. Lastly as far as needs I want it to be street legal and have the same amenities as a traditional car. My brother has some background in electrical engineering and programming so I plan on integrating some cool electronics further on down in the production.
 

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I'm not exactly trying to build a Tesla, but something similar to it where i have all the control over the design.
I realize this will be a tremendous amount of work,


Hi Pirate
I don't want to throw cold water on this BUT
Tesla will have put a huge amount of man hours into their car
Maybe 600 man years - possibly more!

If you want a car this millennium you will have to either use other peoples work or settle for something easier (simpler)

People say things like
"Issigonis designed the mini"
What they mean is
"Issigonis headed up a team of 100 engineers who designed the mini using a lot of parts from existing cars"

There is a huge amount of work in the simplest areas

Range requirements
300 miles is close to the limits with present technology
But if you expect to take a couple of years it may be OK by then - maybe not
Designing a car with the ability to take 300miles of batteries will cause a lot of compromises on other things like performance

I would advice designing with a more modest range and
(1) Hope that you will be able to put 300 miles worth of batteries into a hole for 150 miles
(2) Use the extra batteries on a trailer for your bimonthly trips
 
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