Author Topic: Electric Car Controllers  (Read 13040 times)

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cdtomlinson

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Electric Car Controllers
« on: November 16, 2010, 11:48:12 AM »
I am new to this board, but have been researching alternative fuels, especially transportation, for years.  I guess my main issue is why are electric car controllers so expensive?  I know you are controlling a lot of watts of DC power, but still, there must be a way to do it without spending thousands of $$ to get it done.  Basically, all you are doing is deciding what portion of the whole load to send to the motor to make it drive the vehicle, isn't that correct?  Would love to build a car out of my Saturn, but overcoming the controller cost is a major hurdle.

Thanks to all that can help with this.
Chris

ghurd

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Re: Electric Car Controllers
« Reply #1 on: November 16, 2010, 11:59:30 AM »
The problem is not the watts.
The problem is the Amps!

Plus any efficient speed control is switching the amps with PWM.

Reliably and quickly switching large quantities of amps requires very expensive parts.

There are solutions for some of the issues, but every solution comes with more issues.
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dnix71

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Re: Electric Car Controllers
« Reply #2 on: November 16, 2010, 12:13:37 PM »
Used golf carts might be a place to start. You would need more than one to move a Saturn but the parts would be cheap enough to experiment with.

DanG

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Re: Electric Car Controllers
« Reply #3 on: November 16, 2010, 12:27:04 PM »
Newer style golf carts using 48V systems should be coming off their leases at high-end clubs soon - keep you eyes open...

joestue

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Re: Electric Car Controllers
« Reply #4 on: November 16, 2010, 12:55:36 PM »
short answer:

they aren't that expensive,  how much silicon do you think you should need to control a half megawatt motor? 
right now you can get the basic series wound motor controller for about one cent per watt.

if you can find the igbt's on ebay or surplus sites for 1/4th the standard price you can build your own and save some serious money.
If you want to take the risk, try paralleling 100, IRFP460 mosfets, as you can get these for about $1.39 a piece, and this would get you a series wound dc motor driver rated to about 350v @ 300 amp for about 400$ in parts, but it won't have regenerative braking.
Alternatively, the same silicon could build you a 25Kw 200-260vac 3 phase induction motor drive, and that would be a lot easier than making a 200Kw buck regulator.
but then you better be able to play around with 50mhz processors just to handle the PID...

an alternative to ^that is find an older totaled honda civic or such hybrid car and buy it off the insurance company. i don't know how much money the older inverters are still getting, but the geico agent i talked to the other day said he's never heard of them ever failing in the vehicle, so i should be able to get it for pretty cheap. (dunno what that means though)
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taylorp035

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Re: Electric Car Controllers
« Reply #5 on: November 16, 2010, 02:50:07 PM »
You also could go from the small end and buy 90 v  SHV Castle Creation's ESC's, which are good for 200 A.  But that's only 24 hp.  I bet you could ask Castle to build you one (they make custom controllers), so you would probably not spend $5k, but maybe $2k for something in the 50 hp range (I have no idea what the real price would be).

I have seen that Zilla has closed up shop due to legal reasons.  They were the ones who have built the really powerful controllers, which some were in the lower price range of $1000. 

I have always thought you could put some 20hp plentinburg (sp?) motors in parallel, each controlled by a castle ESC.  It would be simple, easily programmable by people who know how to plug in a usb cable, and scalable.  The motor would cost you ~$1000 and the controller would be $320 for 8kw or more for something like the 90v 200A controller (I think it was $500).  Out put rpm would be ~4000, so you could hook it straight to your transmission.

Golf karts are only good for 3-4 hp from what I know, but maybe there is something better out there.



JW

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Re: Electric Car Controllers
« Reply #6 on: November 16, 2010, 03:14:34 PM »
Im not sure what voltage you intend to run, but heres what I use for 12 dc. This mosfet array can handle 360AMP @ 12vdc continuous It has an instant surge rating of about 900amps for 12 volt.



Its made from solidstate relays wired in parallel, I use a PWM circuit feeding the input to vary the speed control. Its quite powerful. costs about 400 bucks for the raw materials.

JW

ghurd

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Re: Electric Car Controllers
« Reply #7 on: November 16, 2010, 03:30:56 PM »
JW,
SSRs for 12V?
What kind of Vf?
Just seems like they would be pretty inefficient.
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JW

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Re: Electric Car Controllers
« Reply #8 on: November 16, 2010, 04:22:13 PM »
Hi Ghurd,

Your thinking of an AC solidstate relay, these are DC solidstate relays they are MOSFET. they are closing the circuit to negative, I think NPN.      : ) 

JW


cdtomlinson

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Re: Electric Car Controllers
« Reply #9 on: November 16, 2010, 06:41:27 PM »
I am looking to run the Saturn on 96VDC.  from my research and limited ability as an engineer, that seems good enough.  I only need about 35 miles round trip in hilly terrain for 90% of the trips I make and my understanding is that this configuration would work for that.  I expect I could do about 50MPH over that range and be happy as a lark.  But putting out several thousand $$ to experiment would make me divorced and in the dog house.  Not my favorite place to be.

I have a background in electronics, mostly radio, but I can build just about anything.  Designing is my limit.
Chris

JW

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Re: Electric Car Controllers
« Reply #10 on: November 16, 2010, 06:57:33 PM »
The big reason the controllers are so expensive is that the motors use electronic commutation. So the type of motor makes a big difference, brush-less etc. What im describing will run a motor with brushes easily, the problem with PM motors is that they tend to overheat. The back-voltage is not that hard to manage.

Here's a link to a traction motor I intend to build at somepoint-

http://www.flashsteam.com/flashsteam_forum/index.php?topic=108.0

In the end your controller requirements will depend on motor selection.

JW

Tinbendr

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Re: Electric Car Controllers
« Reply #11 on: November 16, 2010, 07:05:07 PM »
See also Revolt, an open source controller.
Nothing is foolproof because fools are so ingenious!

Ungrounded Lightning Rod

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Re: Electric Car Controllers
« Reply #12 on: November 16, 2010, 08:23:33 PM »
In addition to having to control a LOT of power, automotive controllers have a risk cost.

If it sticks on you're going to have trouble stopping.  (Think of the problems they've been having with the Prius.)

And if it shorts you could have an electrical explosion and fire while you're in traffic.

Without a proven (in several crash-tests) design you'll have a hard time finding insurance - which means you may have arguments with the cops and courts if you're driving on the public roads.  B-b

dnix71

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Re: Electric Car Controllers
« Reply #13 on: November 16, 2010, 08:50:52 PM »
An "untested" wall charger for an experimental hybrid/EV caught fire today in California and burned down a warehouse. Neil Young's  hybrid 1959 Lincoln burned along with a lot of his personal stuff.

http://www.thenewstribune.com/2010/11/16/1426692/calif-warehouse-fire-began-in.html

That's the risk of experimenting sometimes.

JW

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Re: Electric Car Controllers
« Reply #14 on: November 16, 2010, 09:06:36 PM »
Quote
And if it shorts you could have an electrical explosion and fire while you're in traffic.

Yes, yes that's when the magic smoke heads for the emergency exits : )

In general these devices fail-open. There are also ziener diodes in parallel with each circuit branch.

JW

willib

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Re: Electric Car Controllers
« Reply #15 on: November 16, 2010, 10:28:39 PM »
Am i wrong or aren't three phase motors and controllers available , with much better efficiencies than a DC motor.
Carpe Ventum (Seize the Wind)

commanda

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Re: Electric Car Controllers
« Reply #16 on: November 17, 2010, 01:03:56 AM »
But putting out several thousand $$ to experiment would make me divorced and in the dog house.  Not my favorite place to be.


Just wait till you sink 10 - 20 grand into lithium batteries.  You'll need more than just the dog house to hide in.

Amanda

cdtomlinson

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Re: Electric Car Controllers
« Reply #17 on: November 17, 2010, 11:31:12 AM »
I am still at the experimental stage, since here in MO, I can't seem to find anyone who will insure an electric car at all, even liability.  Cost again is a big factor.  I'm a teacher, so there isn't a lot of $$ to spare.

It was mentioned that choice of motor makes a lot of difference in the controller, so what does everybody suggest?  I will definitely go DC, again because of cost.
Chris

JW

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Re: Electric Car Controllers
« Reply #18 on: November 17, 2010, 12:42:22 PM »
There's been a few folks who have actually built electric cars, Jerry, Rich H. But I havent see them around lately. I would do some searches on google to see whats out there in the way of kits. I hope your saturn is a stick shift, all the conversion kits ive seen use manual transmissions.

Also if you go the kit route, you will get some tech support.

Good Luck  : )  let us know what you come up with.

JW

taylorp035

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Re: Electric Car Controllers
« Reply #19 on: November 17, 2010, 08:33:57 PM »
I agree with JW, a kit sounds like a much better route.  Performance might be paltry, but you weren't expecting a Tesla Roadster anyways.

I wonder if a beefy forklift setup would do the trick? 

cdtomlinson

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Re: Electric Car Controllers
« Reply #20 on: November 17, 2010, 10:45:43 PM »
I was thinking the forklift route actually.  Most of what I have found deals with brushless motors as a start, but I have never heard that the motor type would affect the selection of controller.  I learn something new everyday.

And by the way, anyone on a budget doesn't want to go the kit route.  Sans batteries, they are about $10,000-$15,000 to start.
Chris

Bruce S

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Re: Electric Car Controllers
« Reply #21 on: November 29, 2010, 01:11:21 PM »
I was thinking the forklift route actually.  Most of what I have found deals with brushless motors as a start, but I have never heard that the motor type would affect the selection of controller.  I learn something new everyday.

And by the way, anyone on a budget doesn't want to go the kit route.  Sans batteries, they are about $10,000-$15,000 to start.
I know a little ate to the dance, but was out of the country where cell phone and internet are rather scarce.

What part of MO are you in? I am in St. Louis.
There are actually quite a few clubs throughout MO. You can look at the website gatewayev.org they should be able to help out.

Cheers
Bruce S
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cdtomlinson

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Re: Electric Car Controllers
« Reply #22 on: December 01, 2010, 11:17:10 PM »
I am in SW MO (Ozark County).  I've been to the gateway site, but there was never anyone near me.
Chris