# my prefect ev



## appleseed (Sep 12, 2010)

hey everyone this is my first time posting here but i have read many forums here already n enjoy hearing about all the projects goin on

in my (future: just planning now) ev ill be converting a 1995 BMW 3 series 2 door coupe. im tryin to get it as good as i can within certain parameters such as 

best range (tryin to get every thing as efficient as i can, hopin for 120 mile range)

good power ( 7-8 seconds 0-60 time, the weight of the car b4 converting is 3100 lbs with ICE intact)

Rev range of electric motor about 4500 RPM or more (will use transmission with clutch to get the car to highway speeds n keep RPM low)

budget: i would hope for around $20 000 after everything but if a motor/controller/batteries dont giv me this performance the budget can be increased

i dont care about really high RPM limit or weight of the motor but lighter is better.

i dont need reverse (transmission can do tht), and regenative braking is a bonus but not needed 

top speed of the car should be about 120km/h (this speed should keep the car with in safe RPM range)

oh btw i dont need the a/c but i will be havin a loud stereo (wont use it all the time) n power steering is a must

thks everyone, i am a beginner but im sure am learning fast by using this forum


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## Automcdonough (Sep 1, 2010)

this is an E30 or E36?
I've run my E30's without power steering, they are light enough to not need it. Much better feel on the freeway too!

The more research you do about components, the more you will realize that every choice involves compromises. No vehicle is "perfect" unless you intend to spend $20k


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## appleseed (Sep 12, 2010)

its a e36 bmw
but if the motor is small enough to fit the controller (possibly batteries too) under the hood make the steering difficult at lower speeds (ex 30km/h)

after further readin i realize my range goal is abit steep but i hope atleast a 60mile range at 60mph is realistic enough (while keepin the performance aspects)

im mostly just tryin to find out what kind of motor would best suit my needs


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## Crash (Oct 20, 2009)

Audio shouldn't hurt you at all... Even a 500 watt system is hardly any power usage off a traction pack.

500 watts / 13.2v = 37.88A...

Obviously, if you need a higher wattage sound system, the math is the same. (1000 watts / 13.2v = 75.76A)

You should have no problem pulling that from a DC/DC converter as long as you have an auxiliary 12V battery still.

You have very reasonable goals. Do you know what motor you want to use yet? Do you know if you want to go AC or DC?


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## appleseed (Sep 12, 2010)

it will be an 1000 watt stereo
but no i am stuck on what type of motor.
im tryin to find a motor tht will move a 3300lb ish car from 0-60 in 7secs

i no dc can do tht but their efficiency isnt as good so i would need more batteries? can anyone tell me a good dc motor for this
any ac motor? brushless motor?

both ac and brushless are most costly but both have improved efficiency so it will help me with my range

one thing i am stuck on is the efficiency of a dc controller vs ac vs brushless

since ac needs a inverter would the inverter be less efficient than a dc controller

how bout the efficiency of a brushless controller? all the information i have found is about the efficiency of the motors but not the motor plus appropiate controller

i figure ill definately need li-ion batteries or atleast li-iron-phosate


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## Crash (Oct 20, 2009)

Well, there's quite a bit of speculation which is more efficient: AC or DC. 

Converting to AC from DC and back (during regen) is less efficient than going directly from DC to DC.

But most DC motor setups are lower voltage which means to achieve the same power goals as AC you'll need more current. But more current means more heat due to electrical resistance which in turn is power loss. 

One of the moot arguments is that AC can spin up higher, so torque can be made by gearing down. However, the same can be said for a DC motor by gearing up. A DC motor will likely make more torque RPM for RPM than an AC motor, whereas the AC motor will make more power RPM for RPM than the DC. 

Gearing up or down decreases efficiency in itself, so depending on what your setup demands, picking a motor that is suited for the RPM range is going to be more important than the efficiency of a motor that doesn't fit your RPM range. For example, an AC motor that spins to 12,000 RPM and has a 92% efficiency isn't going to be as good as a DC motor that spins to 5500 RPM and has an 80% efficiency if your RPM goals are not to exceed 6000 RPM because you're going to lose much of the AC's efficiency with gearing down.

As for regen, you can get regen on some brushless DC motors. 

You may want to look at the UQM motors. They can be pricey at the higher spectrum, but their 50Kw setup may be perfect for what you're looking for. It's a compromise between AC and DC for the most part. No need to gear up or down since it's max RPM is the same as an ICE at 6500. Bolt it directly to the transmission. It makes 325Lbs of tq and can sustain 40HP which is more than enough to push your car beyond 70MPH on the freeway. Voltage is between 300-420, so you have plenty of room to work with. You also don't need high current like you do with DC. 400A is the max you'll need.

I would say this is your best bet. I just don't know how much the system costs, and you'll need to inquire about it.

Going with a system like that would yield you better choices for batteries (maybe cheaper too).

For example, if you went with 110x Thunder Sky 100AH batteries, you would have 407 Volts and 40.7kWh. That'd probably be good for around 120 miles. (Cost would be around $14k)


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## Automcdonough (Sep 1, 2010)

your comparison could be totally bunk depending on the motor controller. The DC motor's brush's are basically a crude DC-AC converter, which sort of kills the mindset of there being another conversion in one case VS another. Those brushless permanent magnet motors have a very broad operating range of 95+% efficiency.


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## appleseed (Sep 12, 2010)

i have looked into alot of motors recently 

i am leaning towards a warp 11 or 13 dc motor

dc for i have heard it is easier to install and allows me more money for more batteries

i am just wondering, do you think tht the warp 11 would be enough to get the 3300 lbs car to 0-60 in 8 seconds or under

i would probably have a zilla 1k controller or 2k if needed (idk wat one is would suit me better) 

or should i just pay the $2000 more for the warp 13, its a big motor so ill have to make sure it fits first lol


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## Crash (Oct 20, 2009)

If you're using a transmission, that should be possible with the 11". Just keep the RPMs below 5000RPM for the longevity of the motor. The DC motors make LOTS of torque. The 11" makes 320Lbs/tq at 1000 amps which is likely more than the car originally had with the stock motor. Hell, my 3400Lbs LT1 Trans Am made 320-ish Lbs/tq and the 0-60 on that was well below 6 seconds. My 3500Lbs LS1 Trans Am made 340Lbs/Tq and had a 0-60 in about 5 seconds. So you should be doing pretty well with an 11" linked to a transmission at 1000 amps as long as your car is below 3500 Lbs.

I hope that all made sense. LOL


Oh, BTW, the 13" Warp motor makes 440Lbs/Tq at 1000 amps. That's a ridiculous amount of torque if you want to go fast.


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## appleseed (Sep 12, 2010)

thank you thts basically what i wanted to here

i went with dc basically because there is so much agruing over ac vs dc and wat is better that the differences arent great enough (for my case) to warrant an extra $5000 for ac or brushless

and those uqm motors the price....i heard around $20 000 +! lol not worth it till tht comes down to round $10 000 or less


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## Crash (Oct 20, 2009)

The Warp11 is a good choice. The main reason you'd want the brushless or AC is for regen. But again, the argument is that you can add more and better batteries for the price difference which more than makes up for the regen to begin with. 

You're making the right choice. Now price out some good batteries and don't buy the controller until you've purchased everything else. When you're using brushed DC, you have a lot of options for controllers, so it should be the last thing to figure into the equation. 

Now you should figure out the voltage and amperage requirements for your project.

You can go with the high voltage version of the Warp11 or the regular Warp11. The difference in price is about $600. The performance difference is that the HV makes more power but a little less torque than the standard Warp11. The HV is also going to make the system more efficient because you're going to pull less current from the batteries.

If you go with the HV, you'll need to make sure you get a controller that handles HV as well, which there are a few of them out there.

Once you figure out which motor you want, then you should start looking at which batteries you want to use and you can size out the pack according to performance and range.


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## meanderingthemaze (Jan 25, 2010)

Sadly, power steering will be the substantial added draw on your pack since it has to continuously run while you are driving. But again, you goal for 60 miles is modest enough to reach.


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## appleseed (Sep 12, 2010)

how much power would a power steering system take? i read tht electric is more efficient than hydrolaic but the exact amount of watts well they didnt say


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## meanderingthemaze (Jan 25, 2010)

appleseed said:


> how much power would a power steering system take? i read tht electric is more efficient than hydrolaic but the exact amount of watts well they didnt say


You're going to have to shop around to find out what loads the different units will draw, I'm sure efficiencies vary. but from everything I've read about, it is one of the significant "add-ons" to a conversion. But again, if you have the money to buy enough batteries, then you just need to plan it in your calcs.

Try searching the forum, It's a relatively common discussion item.


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## Automcdonough (Sep 1, 2010)

pumping a traditional hydraulic system is a huge drain, even on a normal engine you can gain a few % improvement by dumping it for manual steering. An all electric rack is much better because it only draws power when needed, and can be switched totally off when going faster than 10mph.


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## Crash (Oct 20, 2009)

That's a $5K system though. All electric steering will always definitely be a plus and is very programmable. But again, who's willing to throw $5K at steering to keep 3-5% range?


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## Automcdonough (Sep 1, 2010)

really? some newer cars already feature this, should not be so expensive to source a rack from one of these cars.


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## Crash (Oct 20, 2009)

Maybe so, but a real pain to implement. Those boxes/racks are designed for those cars. They're definitely out there in lots of cars but when you're a large company like Toyota, Ford or GM, you can get these things a LOT cheaper and it's not like you're buying off the shelf, so they're OEM grade, not consumer grade. That means they're going to be a lot more specific to the vehicle and stamped out in large cheap mass quantities.

I don't know how possible it would be to retro fit one from a wrecked car to any other car, but considering the time it would take, it may be worth it just to buy the kit.

I did, however, find these kits. They seem way cheaper than some of the others I've seen on the internet:
http://www.unisteer.com/electric_power_steering.html


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