# New DC Controller User Input Requested



## customcircuits (Dec 21, 2008)

After having read many of the posts here and given the lack of quality off-the-shelf DC controllers, I'm considering development of a new controller aimed specifically at the EV community, similar to the Zilla.

I'm relatively new to the EV community (I’m just finishing up my first conversion) and therefore am hoping that some of the more experienced members can help identify and prioritize the most critical/useful requirements for a mainstream controller.

For the conversion I’m currently working on I have built my own custom controller to my own requirements. I wanted a single “Magic Box” under the hood that would contain everything I needed: controller, DC/DC, contactor, heating relay, logic, data acquisition system (temps, rpms, currents)… However, I realize that this is not the standard approach. Are users generally in favor of more integrated controllers like the Zilla or bare bone units like he Curtis? Is there anything the Zilla lacks that would be nice to have? I’m in favor of having the DC/DC and controller combined. Does anyone see any problems with this approach (assuming thermal issues are handled properly)?

Lastly, I’m hoping to market these units to users that are looking for a high reliability (automotive/military grade) street vehicle controller and are willing to pay slightly more for a quality design. And because of this, I intend to only use single high power IGBT modules instead of a bunch of MOSFETS paralleled together like most manufacturers. 

Any input I can get would be greatly appreciated and will go to help refine my current design.

Thanks,
Dave


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## Bowser330 (Jun 15, 2008)

customcircuits, In my opinion people are looking for the "magic box"...more and more DIYers are coming out wanting to build an EV with limited knowledge of electronics, etc...So an integrated controller would be one less thing for them to learn/worry about.

I think offering quality will be your ace, Kelly and Logisystems are getting hit pretty bad on the forums because of their failures, however curtis seems to be the one taking those customers because of their reliability....you could take those customers too...with a quality product...

The zilla has high quality and people paid for it...make yours similar and people will pay for it aswell...I know I would...

Lastly to compete with the already reliable, tried and tested Curtis you would need to offer something that can handle more power than 144V and 500A...might I reccomend 144V and 1000A....?? hehe


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## dimitri (May 16, 2008)

I would prefer a bare bone unit, perhaps with DC/DC, but nothing else, so I can have my flexibility of design and choice of components.

I would prefer single large IGBT type, but I will not pay Zilla price, I don't care how reliable it is, its just not worth that much money to me.

If it has barebone functions like Curtis, it should not cost more than Curtis, hopefully less, since you don't have an army of employees to feed.

It must be 500-1000 peak Amps, and up to 192 V.

just my $0.02


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## elevatorguy (Jul 26, 2007)

I would hope that the different components, dc/dc, relays etc would be user replaceable. Exchange/core program? I think of combo dvd/tv or similar that if one part fails you have to buy a big money controller with subsystems again.
It would be nice to have the ability to tune it for your application too.
Data logging would be a plus as well.
As mentioned before, higher current and voltage than Curtis has a present with reliability... You may have trouble keeping up with demand


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## CPLTECH (Sep 14, 2007)

My suggestion is to read this entire “*Controller*” section of the forum and note the failures of well meaning, scholarly designeers who find that all is not as simple as it may look at first glance. It looks simple on paper, but the real world of EV motor electronics is cruel. Too many of us have had the new generation controllers give up the previously contained smoke within those silicon devices and become very irate when it happens to them.

Yes, EV converters are begging for someone to come forward with a decently priced, powerful, reliable unit. Therefore, all are impatiently waiting for someone to step forward with the magic touch.


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## customcircuits (Dec 21, 2008)

Thanks for all the input so far.

I read every controller post and IGBT/MOSFET app note I could find prior to building my own unit. The two major lessons I came away with are "DO NOT PARALLEL" multiple devices and if you do keep it only a couple units, not 8 and especially not 30 like some. The second lesson is to design in a much greater safety factor given the wide operating conditions. Some manufacturers spec their units right up to the lowest rated components. This type of anaylsis is poor at best. For example, all it takes is for one cap to blow and that starts a chain reaction. If a proper safety factor is designed in this should not happen.


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## DIYguy (Sep 18, 2008)

CPLTECH said:


> My suggestion is to read this entire “*Controller*” section of the forum and note the failures of well meaning, scholarly designeers who find that all is not as simple as it may look at first glance. It looks simple on paper, but the real world of EV motor electronics is cruel. Too many of us have had the new generation controllers give up the previously contained smoke within those silicon devices and become very irate when it happens to them.
> 
> Yes, EV converters are begging for someone to come forward with a decently priced, powerful, reliable unit. Therefore, all are impatiently waiting for someone to step forward with the magic touch.


Very good advice CPL. 

One thing I have always kept in mind while evaluating automation for the company that I worked for many years... the device, whatever it may be, must be extremely good and reliable WRT is PRIMARY FUNCTION. So many things in our world are marketed for their respective "bells and whistles". If it is a Welding Robot, it must be dam good at welding,.... reliably, repeatably, soundly. It's wonderful if it collects data, does neat math, sends u reports at home etc... but if it can't weld really dam good without faulting all the time, it matters not what other functions it has. 

I don't doubt anyones' capabilities... You are starting out the right way, by asking. Some of the very best things are designed by people who have very little, (that's right, very little) knowledge of their intended "widgets' " best features. Many engineers assume they know all they need to know about something and set off to make "the very best one", only to find out later about all the things they didn't realize. The Fender Guitar was designed by someone who never played a guitar. Consequently, he asked many many musicians what they liked, disliked, wanted, hated... dreamed of etc etc. 

Even I have heard of a Fender guitar.. and I know nothing of instruments.

Go for it.

G


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## CPLTECH (Sep 14, 2007)

DIYGuy...
Do/did you work for a robot firm of CRS???


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## JRP3 (Mar 7, 2008)

750-1000 amps, 156 volts or better, something that won't blow up if hooked up to a Warp11. Integrated DC/DC makes sense, though if it could be a modular design that allowed leaving unneeded items out that would be good. Many might like to upgrade their existing controllers but already have a DC/DC.


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## DIYguy (Sep 18, 2008)

CPLTECH said:


> DIYGuy...
> Do/did you work for a robot firm of CRS???


No, I work for a tier one automotive supplier of frames and underbody components, bumpers etc. Strange... I was the welding engineer on the GM electric truck frame, which was built in our plant.. I've worked on many platforms though, over the years. A lot of ppl think the big companies make all the parts.... they "farm out" most of the tougher ones, like frames and cradles.....


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## tj4fa (May 25, 2008)

I agree with the others...Higher amp and volts ratings above what are available.

Keep it simple and easily reparable with possible Line Replaceable Modules.

Fuse it in case of somebody hooking up a pot box wrong or something like that so it can be an easy fix.

Maybe a better heat sync body and weather resistant.

Don't rule out a potential market for simplified AC controller systems. Something simple, reliable and cost-effective would likely convert others to AC systems over DC.


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## booksix (Aug 26, 2008)

contactor control, series/parallel switching, data logging, lots of user adjustability and HBO


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## customcircuits (Dec 21, 2008)

Here are a few more questions I want to throw out there.

I see a lot of requests for higher volts/amps. What volts and amps would you like to see? Are you looking for a street vehicle controller or a racing controller?

The Zilla 1K for example is rated for 1k amps peak and 350A continuous. In practice, what levels of peak and continuous amps are people actually seeing? What setup are you using to achieve these levels? 

What are people's preferences on cooling: conduction, natural convection, forced convection, liquid cooling?


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## booksix (Aug 26, 2008)

I think 1000 will be necessary for a lot of people. As the EV community grows, we come across more people that simply will not be ok with the stereotypical slow EV. People want cars as they know them and power will be necessary. I'm building a street car and I eventually want the ability to pull 1000 amps when I want to lay into the pedal. 

As for voltage, it's be nice in the mid 200's to 300 range...? not really sure, but i see a few cars setup that way (maybe more race rides though)


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## JRP3 (Mar 7, 2008)

As I mentioned earlier I'd shoot for at least 152 volts and 750 amps. Make that reliable and reasonably priced and you'll dominate the market.


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## frodus (Apr 12, 2008)

So, why the higher voltage????

There's an RPM limit for the motors you'd be using the controller with.... and after that the torque drops to hardly anything.... and thats IF the motor coils can even handle the voltage.... and you have to advance the timing so much that it wrecks the efficiency at lower speeds. If you don't advance the brushes you get arcing and efficiency drop.....It seems like people just want higher numbers just to have higher numbers...2-300V... thats assuming you can get a DC motor that will handle that wide of a voltage range.... maybe netgain could handle it, but you'd have to advance the timing quite a bit.



Concerning the real issue at hand... we all want a good controller that gives us higher current and is more reliable....Thats the point right? One module would simplify the power side, but what about the side that switches the gate? the gate drive circuit has to be able to hammer that gate on the IGBT to get it to turn on and off correctly because of the capacitance on the gate.... which can lead to a higher cost due to the higher power/complexity....


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## JRP3 (Mar 7, 2008)

While I agree that voltages around 200 and up are not practical for series DC motors I thought the Zilla allowed higher pack voltages but the motor saw lower voltage from the controller?


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## frodus (Apr 12, 2008)

It sees the full pack voltage, except it only sees it for a percentage of the time. PWM turns the FETS on full, then off. 25% of a 100V pack would be 100V 25% of the time, and 0 the other 75%.... for an average of 25V. The inductance of the motor helps smooth it out a little so it looks more smooth.

I'm just saying, why use the motor outside of its limits.


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## grayballs (Aug 27, 2008)

frodus said:


> So, why the higher voltage????
> 
> There's an RPM limit for the motors you'd be using the controller with.... and after that the torque drops to hardly anything.... and thats IF the motor coils can even handle the voltage.... and you have to advance the timing so much that it wrecks the efficiency at lower speeds.
> 
> Concerning the real issue at hand... we all want a good controller that gives us higher current and is more reliable....Thats the point right?


Practical and reliable,, I vote for that. I don't think that EV's sitting on the side of the road, letting smoke out, or just sitting in the garage because one cannot keep them running, do the EV world any good. Match a modular controller to what is available in DC motors. People need to start seeing the vehicles on the road burning miles rather than electrical parts, or worse yet, sitting in the garage. 
When we start talking much higher voltages, I think we should be talking AC drives, as I believe that is where we are all headed at some point.


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## Bowser330 (Jun 15, 2008)

the reason i mentioned 144V and 1000amps is because thats what the DC motors that most people are using are reliable at...

156V is the maximum the DC motors can take without failing, is what I've read, and seeing as you are building a safety margin into your controller, I think thats what curtis, etc, have done with creating controllers to 144V...

1000 Amps is requested because according to my 144V graph for the 9" FB1 motor, 1000 Amps would put the motor at 250ftlbs Torque and 100hp...

Get two controllers and two motors and you have yourself a serious sportscar setup...500ftlbs and 200hp...


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## JRP3 (Mar 7, 2008)

frodus said:


> It sees the full pack voltage, except it only sees it for a percentage of the time. PWM turns the FETS on full, then off. 25% of a 100V pack would be 100V 25% of the time, and 0 the other 75%.... for an average of 25V. The inductance of the motor helps smooth it out a little so it looks more smooth.
> 
> I'm just saying, why use the motor outside of its limits.


I understand how PWM works, but my understanding was that the Zilla allowed higher voltage pack while sending lower peak voltage to the motor. So you could have a 200-300 volt pack with only a 156 volt peak to the motor. The benefit would be that the motor would not experience a voltage sag as the pack is discharged, and of course smaller wiring could be used. I could be completely mistaken though


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## JRP3 (Mar 7, 2008)

Bowser330 said:


> the reason i mentioned 144V and 1000amps is because thats what the DC motors that most people are using are reliable at...
> 
> 156V is the maximum the DC motors can take without failing, is what I've read


A number of people are running Warp9 and 11's higher than that.
Whatever voltages and amps you build for one goal is that the controller should be able to handle a Warp11 without dying, something no current controller seems to be able to do, other than the Zilla.


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## frodus (Apr 12, 2008)

JRP3 said:


> I understand how PWM works, but my understanding was that the Zilla allowed higher voltage pack while sending lower peak voltage to the motor. So you could have a 200-300 volt pack with only a 156 volt peak to the motor. The benefit would be that the motor would not experience a voltage sag as the pack is discharged, and of course smaller wiring could be used. I could be completely mistaken though


unless there's a transformer inside, its really 156V average, but the peak to peak is 200-300V.... but the duty cycle is 50%.


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## frodus (Apr 12, 2008)

grayballs said:


> When we start talking much higher voltages, I think we should be talking AC drives, as I believe that is where we are all headed at some point.


Exactly. Once you start talking higher voltage, AC is the direction to go. Cheaper off the shelf motors.... but expensive AC drives.




bowser330 said:


> Get two controllers and two motors and you have yourself a serious sportscar setup...500ftlbs and 200hp...


see, now you're talkin, if the motor is the limitation, not the controller, add another motor for more HP.


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## Bowser330 (Jun 15, 2008)

frodus said:


> see, now you're talkin, if the motor is the limitation, not the controller, add another motor for more HP.


but what about direct driving two 9" motors...would that work?

what if they were both set at 5:1 ratio?

5000rpm motor = 1000rpm wheel

That means about 60-ish mph (at 1000 wheel rpms) 
A 9" FB1 at 144V at 5500rpm is going 60-70mph would give you 90% efficiency (according to the motor graph I have)...

It is still around 80% efficient at 3000rpm (which would translate to 35-40mph)

....

LETS GET THAT 1000AMP controller out ASAP!!! haha, jk...


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## customcircuits (Dec 21, 2008)

Thanks for all the input so far. It helped us narrow down the power stage design. 

Originally, we had hoped to develop several different controllers based on using single IGBT power modules. However, these are only available up to about 800A (at 600V) and are not very efficient at this level. We did find a very efficient module which we can create a 1000A controller using two IGBTs with a Vce that is 30% less than what the Zilla uses. We had hoped to use only a single IGBT for improved reliability but have settled on using multiple IGBTs so long as each unit is independently current monitored.

Our goal now is to find out what people consider to be the most important user inputs and outputs. Obviously you have to have an enable input and a throttle input but what else? What are your thoughts on the following or any others you might think of?

motor rpm
motor temp measurement
transmission rpm 
contactor control (single, reversing, motor paralleling? )
battery temp measurement
power steering control
heater control 
led status indicators ( and used for what specific indications? )

thanks for the input-
Dave


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## JRP3 (Mar 7, 2008)

Most useful, (my opinion):
Contactor control 
Motor rpm


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## DIYguy (Sep 18, 2008)

JRP3 said:


> I understand how PWM works, but my understanding was that the Zilla allowed higher voltage pack while sending lower peak voltage to the motor. So you could have a 200-300 volt pack with only a 156 volt peak to the motor. The benefit would be that the motor would not experience a voltage sag as the pack is discharged, and of course smaller wiring could be used. I could be completely mistaken though


This is accurate, as long as the pack voltage is not higher than the controller rating. I plan to do this with my controller also. I'm probably going to run a nominal pack voltage of 180 and limit the motor to 170 max.


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