# Why so expensive ??



## Harold in CR (Sep 8, 2008)

I have been reading this and other forums, trying to decide what controller I might need for my Jack & Heintz 500 amp Aircraft starter-generator.

The Curtis seems to be the most dependable, but, $1500.00 seems a little steep ???

My little bit of experience with controlling an electric motor (DC) is a ¾ HP 12V DC motor on a homebuilt portable sawmill. I bought a PWM off Ebay. Had problems with burning out mosfets? or copper tracks? on the Circuit board. Finally found someone that knew someone, that got me the answer to my problem. It was high voltage ?? spikes backfeeding into the controller. A couple capacitors or resistors placed across the motor lugs to ground, stopped the problem. This has and is working well after 6 years ??

I paid $65.00 for a 120 amp pot controlled PWM. ??? Is there so much more to an EV car syatem, to warrant the $1600.00 ?????? You can hold the thing nearly completely in the palm of your hand ??? 

What am I not seeing ???

I plan to run the motor on 96 volts, and have some steep hills to climb back to my house. Probably make up a hybrid charge on the go system, to help keep decent charge in the batteries, for the trip up the mountain, 500 meters altitude in a 3 mile run. ??? 

ANY details y'all can share, would be greatly appreciated. Thanks


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## TX_Dj (Jul 25, 2008)

If you had a 120A 12v controller, that's 1440 watts, or 1.44 kW.

However, a controller capable of 550A at 120V = 66 kW.

Perhaps that's what you're not seeing?

The components are larger, more expensive, lots more design work has been done, there's a warranty, etc, etc...

$1500 is actually a fairly decent price for a curtis controller, depending on which model it is.

If you want to save pennies, go get a cheapie like a Kelly. The trade off is wondering if it's going to work, wondering if it's going to set your car and house on fire, wondering if you'll ever get it repaired or get your money back when it does blow out.

With Curtis, you're paying for peace of mind knowing that you're buying from the #1 best track record PWM DC motor controller manufacturer for EV applications.


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## ClintK (Apr 27, 2008)

Harold in CR said:


> I plan to run the motor on 96 volts, and have some steep hills to climb back to my house. Probably make up a hybrid charge on the go system, to help keep decent charge in the batteries, for the trip up the mountain, 500 meters altitude in a 3 mile run. ???
> 
> ANY details y'all can share, would be greatly appreciated. Thanks


With 96 Volts you have quite a few options when it comes to controllers.

Quick search through my bookmarks of EV suppliers...
Kelly for $550 (up to 96V) at beepscom.com
Curtis 1221C (up to 120V) for $1075 at evsupplystore.com
Navitas (72-96V) for $1129 at cloudelectric.com

Definitely shop around... I frequently see prices vary up to 25% between suppliers on a lot of EV components.


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## Harold in CR (Sep 8, 2008)

OK. In my old age, I miss figured the Killiewinkles involved. 

The price I posted WAS the Curtis 1221C. $a grand is a LOT more reasonable. Guess some stores don't mind gouging, anymore ??? 

Thanks for the responses.


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## TX_Dj (Jul 25, 2008)

That's the truth!

With the recent fuel price surge, there was a large increase in demand for EV parts. Many suppliers simply raised prices to mitigate customer frustrations that come with long lead times. I.E. raise the price, reduce demand, keep customers happy by getting the product to them in a few weeks instead of 16.

Others have more stock, and/or better plans with the manufacturers, and can either deliver more quickly and/or don't care if the customers get upset when they have to wait 10 weeks to get the product they paid for.

Curtis makes good stuff. $1000 is much better than $1500 in my book, but if $1500 means I get it today instead of next year, I might be willing to shell out the increase depending on my timeline.


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## KiwiEV (Jul 26, 2007)

TX_Dj said:


> If you had a 120A 12v controller, that's 1440 watts, or 1.44 kW.
> 
> However, a controller capable of 550A at 120V = 66 kW.
> 
> ...


Can't argue with you there. Bob from EV America says he only has a 2% failure rate with Curtis controllers. That's a tiny number when you realise the installation of the Curtis Controller is out of Curtis' control. 
Hehe, I almost made a play on words there.


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## ga2500ev (Apr 20, 2008)

To answer the OP,

What you are not seeing is the engineering design that it takes to get a controller to work even close to properly. Or the taxes, insurance, infrastructure, salary, and the millions of other expenses that a company has to pay in order to be in business.

The average controller is about $150-$200 in parts. If you're building one from yourself, everything else is time and frustration. But if you are building hundreds for others, that's a whole 'nother ball game.

I think this is where a community based open source controller is going to get some traction. There are many who will put in the sweat, but do not have the design chops to put a controller together. However, those same folks can follow a schematic and a list of instructions. That's why there are a minimum of 5 different home brew design threads floating around the board right now. I truly believe that we will distill a useful design from the discussion and that will offer another avenue for getting a controller going.

But the cost isn't going to drop. The overhead and the demand are both rising, not falling. So expect decent controllers to get more expensive, not less so.

ga2500ev


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## ClintK (Apr 27, 2008)

ClintK said:


> With 96 Volts you have quite a few options when it comes to controllers.
> 
> Quick search through my bookmarks of EV suppliers...
> Kelly for $550 (up to 96V) at beepscom.com
> ...


I decided to add a wiki page of all the EV suppliers I've been checking with. Prices vary so much I think it could be a good asset to people. http://www.diyelectriccar.com/forums/showthread.php?p=80303 I know I'm missing lots of sites/information, but if you've got a few more to throw in there please do!


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## Harold in CR (Sep 8, 2008)

I used to have a newspaper clipping of some guy, in Ft. Pierce, Florida, that was doing backyard conversions. Recently found that he has become a conversion business and I have found his phone number and name. 

Next trip to Florida, guess who's getting a visit ?????????? He's 20 miles from where I visit my family. !!!!!!!!!!!!


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## ga2500ev (Apr 20, 2008)

Harold in CR said:


> I used to have a newspaper clipping of some guy, in Ft. Pierce, Florida, that was doing backyard conversions. Recently found that he has become a conversion business and I have found his phone number and name.
> 
> Next trip to Florida, guess who's getting a visit ?????????? He's 20 miles from where I visit my family. !!!!!!!!!!!!


What kind of controllers does he use?

ga2500ev


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## Harold in CR (Sep 8, 2008)

It's GrassRoots EV, and he has Kellys and Logisystems. HAD Zilla, but, I guess they are not building, anymore , or something like that. ???


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## Harold in CR (Sep 8, 2008)

When I originally posted this thread, I was trying to think about what the parts were, for the homebuilt controller we were trying to build, in 1980. 

I do know, we had a blue capacitor, about 3" dia, X 4-5 inches tall. We had 3 --200 AMP Transistors, that were to be switched off and on, by a "Pulser" circuit. The transistors were about 2.5 inches square, and ½" or so thick. We had them mounted on a piece of Alum Channel, 3/8" thick, X 12" long, and planned to orient the channel, so air would flow through the channel, not over it. 

There was assorted Diodes, resistors, and what not ??? I'm NOT into Electronics. Give me 120-240--7200-12,500--, 34,500 volts, and I can do whatever you need.

My point is, I also mentioned a PWM I bought, to supply pulsed DC to a ¾ HP 12V DC motor, on our sawmill. When we had trouble burning out mosfets, the guy I bought it from, built a copper clad board, with more powerful conponents on it, to be run by the PWM. It didn't do what he hoped, but, this is what I have been sleeping on. 

IF i can buy a PWM, rated at 100 amps, it should pulse a POWER Board or BIG transistors--Mosfets-- IGBT's, (whatever they are), correct ??? The PWM will only send a controller signal to that board, and the board on to the motor ???

I understand all the math and design work involved, but, I just can't see it being all that difficult ??? At my age, I don't have the time, OR the school available, to learn any of this stuff. 

What about buying a controller from a used outfit, like I posted a link to, in another thread, and upgrading the proper components to handle the load ???

There has GOT to be a way for some smart electronics guy, to work up a controller, that won't cost $1000.00, and take the place of that Zilla that everyone seems to think is the better controller, and not available ???

Don't need any putdowns, just help me understand why this is such a tough nut to crack , OK ???


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## ga2500ev (Apr 20, 2008)

It's such a tough nut to crack because of the power involved. Hundreds of amps of current magnifies every design flaw.

As for the cost i'm pretty sure that discussion has gone on here. Someone selling controllers needs to make a profit. Also because it's not easy to do and there's a small market, there is a huge markup.

The power electronics from the driver to the motor is the critical part. The PWM electronics isn't too difficult to handle.

ga2500ev


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## Wirecutter (Jul 26, 2007)

ga2500ev said:


> It's such a tough nut to crack because of the power involved. Hundreds of amps of current magnifies every design flaw.
> 
> ga2500ev


This reminds me of the answer to the question:

"Why does a divorce cost $30,000?"

"Because it's worth it."

I have to agree with ga2500ev here. Going to the extremes of *anything* tends to enhance weirdness. This applies to deep sea diving, high voltage, high current, high frequency, and even very low frequency, as in radio. Harold sounds like he may come from a power transmission background. Perfect example - look at the difference between how you wire across your house and across your state.

With the EV controllers, you're generally talking about high currents - hundreds and sometimes thousands of amps. With PWM controllers, you're switching all this power pretty quickly considering the currents involved.

Now let's move sideways a bit and consider that a major application for Curtis controllers, for example, is in golf carts. Search YouTube for golf cart and you can see some of the crazy abuse heaped upon rented electric golf carts. So Curtis controllers have to be built to last, rather than becoming a maintenance headache for the golf course operator.

In practical terms, when you switch so much current on and off, your power rails might want to sag and bounce around. This can be very bad for your switching elements (transistors, IGBTs, etc) Also, a motor can act like a flywheel or a spring in the electrical realm - you kick it to get the wheels to turn, but you have to remember that it can and will kick back.

Having said all that, I'm one of the people here that hasn't learned that you can't make your own controller. I'm in the early stages of building one, and I'll share my experiences here. 

-Mark


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## ngrimm (Oct 19, 2007)

Deleted by Norm


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