# General questions about my EV plan.



## madderscience (Jun 28, 2008)

Hello and welcome.

You sound like you have a VERY ambitious plan and you sound like you need to spend some additional time educating yourself on some of the fundamentals of EVs and electricity in general. There are books on the subject, or start with the wiki here. Not saying what you want is impossible, but I hope you have significant budget and time to achieve this. 

Strongly suggest you look at how other high performance EVs have been constructed (think white zombie, or tesla depending on the parameters you wish to maximize) and do your best to build something similar. Unless you are a genius engineer of have access to one to help you, you probably aren't going to improve much on what teams of others who have been at this for years have accomplished.

There is someone in my local EVA group who is working on a ground-up conversion of a late model corvette and who has similar goals to yours. He is in it several years and tens of thousands of dollars so far and he still has a lot of work to do. I've been driving my car as long as he has been building his. Just sayin.

In response to some of your questions:

Any AC motor you are looking at is only going to have max torque up to some defined RPM point based on the maximum voltage the controller/battery can deliver to the motor. After that point, torque drops off; the curve depends on the type of motor. So you need to figure in your caclulations whether the torque available from your motors at maximum desired speed is actually enough to get there. It doesn't help if a motor can spin at 8000 rpm if it puts out zero torque at that speed. Similar story for DC motors though the physics behind it is different.

If you do direct drive, you don't need a clutch. Just bolt the motor shaft straight to the drive shaft. You need a lot of motor and controller to do this and have both good acceleration and good top speed. With an AC system, the gear ratio is usually 8 or 10 to 1 in direct drive. With a DC system and a big ass controller (soliton or zilla) it is usually 4 or 6 to 1. 

If you want 450V across the motors (not likely you actually need that much) you do need to consider voltage sag on the batteries. Do some research to figure out what internal resistance the batteries provide (along with the resistance of you wiring, etc) and then you can compute voltage sag at some amount of amps or KW depending on what units you want to think in. In any case, a 450V nominal pack with sufficient amp capacity is probably enough to get a car to 150mph presuming the rest of the system didn't constitute a weaker link in the chain.

Safety is a major concern with anything that is designed to go 150mph, electric or not. read up on high voltage safety and take classes if you aren't experienced with this and take advice of the experts. The car is going to need fusing and circuit breakers capable of breaking a massive amount of amps and the maximum voltage of your battery pack. It is true that AC motors won't run away if their controller power section fails. It is possible with DC motors hence the need for fuses and circuit breakers and in the case of something like what you want, some other kind of kill switch. (w. zombie has a big custom made jumper the driver can yank to cut power though I bet it makes a big spark when they do it)

You can reverse without a tranny, AC or DC. AC requires nothing special. DC will need a reversing contactor.

Yes, double the amp hour capacity of the battery should roughly double range. I say roughly because of course you also doubled battery weight. assuming the car is light and sleek, a 16KWh nominal pack (450v, 40ah more or less) might give a useful range around 50-60 miles at normal driving speeds. (not at 150mph)

look at what motors others are using in their conversions. If nobody is using the UQMs there is a reason. (most likely, they won't sell to individuals which is true of a lot of OEM motor builders) Warp motors are very popular in conversion on the DC side. you can look at metricmind.com for some AC systems available to converters but I don't think any of them have the horsepower you want.

No, electric motors don't need a starter. You don't need a flywheel either unless you are keeping the clutch/transmission which is a common thing to do in conversions as it is easier and cheaper than direct drive.

I drive my car in the rain all the time, and I am still alive. That said, basic weatherization and insulation of high voltage stuff is a good idea in a driveable street car. The higher the voltage, the more important it is to do a good job with this. You want a very high voltage car.

Good luck, and as stated above, first suggestion is to do lots of research.


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## GerhardRP (Nov 17, 2009)

Lovi said:


> Hi everybody!
> 
> I have several questions about the EVs.
> My plan is to make a car which is accelerating well, but don't go faster than 150 mph. (240 Kmh). I want it to be AWD with two motors. So here are some questions.


 Before we try to help you reach this goal, do you have a budget if at least $100K? Something less ambitious might make a better start.
Gerhard


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## Lovi (Apr 25, 2011)

Thank ou for the answers! The white zombie is a realy exciting project, i would totally satisfied with a 3.5 sec 0-60 acceleration, and sure i don't want to spend ten thousands of dollars.
And the price calculation is depending on my wishes. And may i have to make a compromise.
@madderscience you talking about AC motors sometimes, but I'm thinking on DC systems because of the price.
In other case it's not so unequivocal the torque of the netgain. UQM have a simple and clear diagram.
From 0 rpm to 1250 900Nm, than decreasong.
http://www.uqm.com/pdfs/PP200 Spec Sheet 3.30.11.pdf
On the NetGains Warp motor's diagrams there are numbers from 0-5000 rpm and 0 to 200 Nm.. Strange.
http://www.go-ev.com/images/003_20_WarP_11_Graph.jpg
They says the peak torque is 860 Nm (WarP 13), but there are no diagrams. By the was UQM PP 200 have much better weight/torque rating (it's another thing that most of us, can't buy them).

Thank you for the high voltage safety link, it doesn't seems that so dangerous as i thought. My grandfater is an electrician, it's similar to the standard euripean 230V ~32A

One more question:
12.
Do the motor controller know when do it need to power the motor? I mean in with the CID engines we have to push the clutch at lower engine RPM.

Sure, i still need to research much more, I still have 1-2 years until I start building it.


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## Yabert (Feb 7, 2010)

Lovi said:


> And the price calculation is depending on my wishes. And may i have to make a compromise.


I think you will need to start with battery price because you can easely find few motor / controller set-up able to give 250-350 hp for 6-7K$ but if you don't have a 400 hp capable battery pack at 30000$ the motor will do nothing.


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## JRP3 (Mar 7, 2008)

Lovi said:


> and sure i don't want to spend ten thousands of dollars.


You can't really do anything close to what you are suggesting without spending tens of thousands of dollars.


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## Lovi (Apr 25, 2011)

I can build my wishes in aroud 40.000$ (just the electric materials). It's totally okay.
For the question from @GerhardRP:
"do you have a budget if at least $100K?"
No I don't, but around 40K could be enough. I hope!


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## Yabert (Feb 7, 2010)

Lovi said:


> but around 40K could be enough. I hope!


 
40k$ seem ok..., but I think you need to do a right selection of components from first try...... so learn before buy something!

And don't forget, put 30k$ on battery, charger, BMS, etc. and only 10k$ on motor, controller, transmission assembly.

Oh! and all this is only true if your car will be under around 1300 Kg (2860 lbs).


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## Lovi (Apr 25, 2011)

Sure, first of all I look for answers to my questons and planning a lot.
Than plobably there will be another one post with the plans.
I don't want to do any dumb thing, it's great to get some help from you guys. Thank you!

Oh, ahd *one more question*, there is no more important than this one!
How can I make this car street-legal in Europe(an union). Or don't you take care about it, just driving?


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