# Contactor bypass Turbo Mode



## BenNelson (Jul 27, 2007)

For a while, I have thought about using contactors to bypass the PWM controller, while adding in extra batteries for a "Turbo-Mode"

Yes, I know that having the extra batteries in all the time is better, more efficient, etc, etc. but I am already maxed out on my voltage.

I am running a Curtis 400 amp 72V controller in my EV Geo Metro.

My idea was to use two reversing contactors to take the controller out of the battery loop, then connect in two additional batteries, and connect all eight batteries directly to the motor.

I tried it and it works!

Normally, I can get this car up to about 45 mph, although it's pretty slow to get from 35 to 45.

Now, I took it out for a run, got up to around 45, let off the gas pedal (no more amperage for the controller) and hit the turbo. The contactors kick in and connect max amps of the 96 volts straight to the motor.

I felt like a drag-racer! The car quickly accelerated to 55 and then worked up to 60 mph.

Here's the contactors I used









And here's the octopus of cables it became once everything was hooked up.









I added two more batteries, just on the floor of the passenger seat, and added the turbo switch there. Those two batteries also provide the 24V to power the contactor coils.

http://gallery.me.com/benhdvideoguy/100952/DSC_0207/web.jpg

Again, this is all sort of an experiment, and just a cheap way for me to try to squeeze a little more speed out of the car without spending the big bucks on upgrading the controller, charger, etc.

Any advice on what I would need to do to make this a reliable, permanent modification?

I know I need to get diodes on the reversing contactors.

What about back EMF to the motor? When I turn the turbo mode off, the contactors just kick back to the controller being in the loop. Since the motor is already spinning, is it going to feed bad electro-magnetism into the controller and fry it?

Also, do I need to re-pre-charge the controller capacitors? I don't think I do. Capacitors should stay charged longer than a few minutes, shouldn't they? Not sure though.

All advice welcome, I don't want to fry my controller!

Thanks,

-Ben

http://www.evalbum.com/preview.php?vid=1595


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## major (Apr 4, 2008)

BenNelson said:


> What about back EMF to the motor? When I turn the turbo mode off, the contactors just kick back to the controller being in the loop. Since the motor is already spinning, is it going to feed bad electro-magnetism into the controller and fry it?


Hi Ben,

Why would this be any different than letting up on the throttle pedal and coasting downhill reaching a higher speed than normally possible and then pushing down on the throttle again when you level out? The controller will output maximum voltage to the motor, but it will draw little current and produce little torque, so the vehicle will slow. That's my take on it.

And, the controller may have a bleed resistor to discharge the caps. So a precharge may be needed even if it is only off for a few minutes. Then again, you may be able to keep the 72 volt input to the controller while in by-pass.

Fun playing with this stuff, isn't it. But you never know all the quarks, so a blown controller is still a possibility. The cost of going where no man has gone before.

And be careful out there. You lose safety when you by-pass that controller. What happens if the by-pass contactors weld up? You better have a plan B. Safety disconnect of some sort.

Regards,

major


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## BenNelson (Jul 27, 2007)

Yep, of course I have another contactor to disconnect in case of emergency.

Also, since the bypass is TWO contactors, I think the odds of both of them welding up simultaneously is not that high.

If one welded and the other didn't, it would disconnect power to the motor, and the car would just coast to a stop.


I always hear about "back EMF" and the likes when motors and contactors are involved. I don't know too much about all that and just don't want to fry my controller!


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## JRP3 (Mar 7, 2008)

Cool setup, I've seen a few others doing this as well. You can test your controller caps to see how long they hold their charge, just disconnect the pack and see how long they take to drain down.


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## ice (Sep 8, 2008)

Nice work!


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## 300zxev (Dec 5, 2008)

Great to see this actually getting tested.
i did post a number of queries regarding this sort of bypass in the past, but never scraped up enough ideas to draw any conclusions.

I was planning on implementing a bypass contactor, not to add extra batteries, but in a 144V setup to bypass the controller in the effort to supply more amps to the motor than the controller would allow.

My setup was leading to having a hi cap circuit breaker as emmergency disconnect before the "turbo contactor". So can be used in emmergency regardless.

I hadn't thought of using a reversing contactor ... I had planned on 2 contactors, one with precharge for the controller (which stays on) and one just to bypass. The reversing contactor seems a more economical option ... (same amount of unknowns ... but economical).

I did receive bit more practical suggestions from an electrical forum i subscribe to which suggested i use a flyback diode between the controller and the motor ... but didn't receive any suggestions on which diode would be suitable.

If you are still testing this setup, I would be interested in hearing any conclusions you come up with ... How are the batteries holding up ? any notice in the battery temp ? motor temp ? are you monitoring the amps drawn when directly connected ? Let us know what diodes you'll be looking at if any


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## BenNelson (Jul 27, 2007)

This is VERY experimental.

I have only done one run with it so far.

I totally pegged out my ammeter. I have a 400 amp 72V Curtis controller, and only a 300 amp ammeter.

One thing I would like to figure out is how to control current draw when connecting directly to the batteries like this.

One person suggested that I simply use the manual transmission to do it. Since higher gears draw more current, simply use the TURBO in a lower gear to reduce current.

After my road test, I did pull over and manually checked temperatures. That is to say that I put my hand on the motor, controller, cables, and batteries to feel if any were warm.

The motor, controller, and contactors were all dead-cold. One battery was warm, but all the others felt as they normally would. That battery was known to always have a lower voltage than the rest. I might have to keep my eye on that one.

One battery cable was warm. It was as heavy-duty as the rest, but it was coming off my most positive battery post, where I have a 250 amp slow-blow fuse and a couple other small ring connections.

I think the heat may actually have been generated at the fuse and simply conducted into the cable.

I have since swapped that cable out for a different one, so I will be able to tell next time if it was the cable and terminal, or its location connected to the fuse.

I don't know a whole heck of a lot about diodes, other than that they let electricity go one way and not the other! I will have to learn more and figure out what I need, that's why I am taking it slow with this TURBO circuit, and trying to figure it all out WITHOUT blowing up my controller!


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## judebert (Apr 16, 2008)

I believe John Wayland did this in his White Zombie, for drag racing. His contactors welded shut; he had to pull an emergency breaker that he had in his cabin. The spark was so big his opponent thought he was taking flash photography.

It'll work. But it's not all that safe. You might be better off with a contactor controller. The version with the big plywood disk with copper plating was always interesting to me.


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## bblocher (Jul 30, 2008)

Pretty cool. I would at minimum get another amp guage in there to see where things are. Despite temps, you should still make sure you're not over amping the motor. My other concern is how many amps you're pulling from the batteries and how that may affect life. The lower gear idea will work as long as you're not over revving the motor. So as long as you can keep an eye on RPM and AMPs you're good.

Of course you probably should just get the next size up controller. 
Either way fun to experiment!

I can't imagine what would happen with a direct connection on my setup...scary.


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## BenNelson (Jul 27, 2007)

Too bad a Curtis 1231 would cost more than I have spent on the entire project, including the car, motor, batteries...EVERYTHING!

I am hoping to be able to "road-test" a friends 144V Open Source controller, once he is done building it!


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## ice (Sep 8, 2008)

keep us updated always!


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## BenNelson (Jul 27, 2007)

I ran the turbo again today while out running errands.

This time, I engaged it while in third gear. The lower gear did limit the amperage draw.

The ammeter shot right up to 300 and then came back down into measureable range a few seconds later.

I only ran the turbo for maybe 7 seconds. Acceleration was fairly brisk, and I didn't want to speed!


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## ice (Sep 8, 2008)

Nice! 7 seconds turbo!


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## EV59RAG (Oct 6, 2008)

Any update?


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## bblocher (Jul 30, 2008)

EV59RAG said:


> Any update?


Not a good sign when the guy testing this doesn't respond.


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## hondo (Mar 30, 2009)

Ben, we haven't heard from you in a while, I hope it is still working. I am going to try a similar experiment on my Fiero. I am running my fiero at 48 or 96 volts using a series/parallel swithch. I have 3 banks of resistors and a make before break switch for the contactors for each of the 4 circiuts. (no "controller", just contactors) It keeps you very busy while driving but it works and it was cheap. Anyway, I have an old 48 volt 250 amp curtis controller that I am going to use on this experiment. I am going to wire the contoller as usual, but I will wire in a contactor in parallel with the controller that is engaged by a micro switch when the pedal gets to full throttle. I will not be bypassing the controller. If it blows, I'm only out a cheap controller. But the reason I want to leave it in the curciut instead of bypassing it is because when you let off the throttle and the contactor disengages, the controller is there to carry some of the amps. I am worried about the contactor sticking shut if you let off the pedal while pulling 500-1000 amps. If this works, I can try it with a 400 amp 96 volt controller. Maybe we could meet and conpare set-ups sometime, I am just north of you in Appleton.


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## major (Apr 4, 2008)

hondo said:


> I am going to wire the contoller as usual, but I will wire in a contactor in parallel with the controller that is engaged by a micro switch when the pedal gets to full throttle. I will not be bypassing the controller.


Hi hondo,

How do you figure you'll not be by-passing? All the current will flow thru the contactor and none thru the controller. That's a by-pass. The controller will still be connected in the circuit, but because the contactor has a lower voltage drop, or resistance than the controller, it will conduct essentially all the current. The danger is that when you come out of by-pass, the current will be higher than the devices in the controller can handle. Even if you lift completely off the throttle, setting the controller to zero duty cycle, the freewheeling diode will be in the motor circuit. Too high a current for too long there, she'll blow. No way to control that.

I've mentioned before, maybe in this thread, that older forklifts used by-pass pretty much as a standard for years, called 1-A. But those controllers were designed to do this and had control of the 1-A contactor. By-pass is a legitimate strategy, but needs to be correctly implemented. You're willing to risk an old controller. Go for it. Might just work.

Regards,

major


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## rmay635703 (Oct 23, 2008)

ice said:


> keep us updated always!


http://ecomodder.com/forum/showthread.php/ben-nelsons-electro-metro-build-thread-848-105.html

He does, just not at this forum


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## hondo (Mar 30, 2009)

Thanks for the reply Major! You would think that all of the current would go through the contactor but, I have found on my fiero that it doesn't. I have indicator lights on my dash to tell me when a contactor is on. When driving if I have the throttle on to where the last two lights are on (Direct & 1 resistor) the resistor continues to put out heat. I know this because I have this resistor mounted in the heater box where the heater core used to be and is my source of heat for these cold Wisconsin winters. It doesn't put out as much heat as when it is the only contactor on, but it does put out heat. But you are right in what would happen when I would disconnect the bypass, but I guess how much it would effect the contoller can't be known for sure without testing.


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## major (Apr 4, 2008)

hondo said:


> You would think that all of the current would go through the contactor but, I have found on my fiero that it doesn't.


hondo,

I guess the next question is: So what? The current takes the path of the least resistance, in proportion. If the non-by-pass path has a resistance low enough to conduct around the by-pass circuit, let it. You're better off. But then why does your by-pass circuit have that much resistance? Got some burned contact buttons there?

Regards,

major


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## hondo (Mar 30, 2009)

Major,

I might, I haven't checked them in a while. That would explain things. Anyway I am going to tear it apart tonight and test this idea out. I think the main thing is to not just floor it from a stop. I have an older Yale electric fork lift here at my business and I notice when you floor it, it starts out slowly, and after it picks up a little speed you can feel an additional kick-in. I wonder if it is the by-pass you talked about. 

Thanks for your input
Hondo


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## EV59RAG (Oct 6, 2008)

hondo said:


> I am running my fiero at 48 or 96 volts using a series/parallel swithch. I have 3 banks of resistors and a make before break switch for the contactors for each of the 4 circiuts. (no "controller", just contactors) It keeps you very busy while driving but it works and it was cheap.


Hondo, I am very interested on your series/parallel setup. Do you have a website where you explain more? or maybe a link that you can give so i can further research this setup. Do you have a thread on this forum explaining this?


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## E4mula (Mar 31, 2009)

hondo said:


> Major,
> 
> I might, I haven't checked them in a while. That would explain things. Anyway I am going to tear it apart tonight and test this idea out. I think the main thing is to not just floor it from a stop. I have an older Yale electric fork lift here at my business and I notice when you floor it, it starts out slowly, and after it picks up a little speed you can feel an additional kick-in. I wonder if it is the by-pass you talked about.
> 
> ...


The bypass contactor on your old Yale forklift would only activate at full throttle after the controller has ramped up as much as it could. It was originally used to bypass the voltage drop across the SCRs or mosfets in the controllers.

Activating the contactor from a stop is a good way to weld or blow out the tips.


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## hondo (Mar 30, 2009)

To EV59RAG- 

No I don't, but it is not that complicated. It is kind of like 2 knife swithches that are hooked together. I built it out of 1/4" thick copper strips. I will take a picture tonight before I take it apart for my experiment.

Hondo


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## EV59RAG (Oct 6, 2008)

hondo said:


> To EV59RAG-
> 
> No I don't, but it is not that complicated. It is kind of like 2 knife swithches that are hooked together. I built it out of 1/4" thick copper strips. I will take a picture tonight before I take it apart for my experiment.
> 
> Hondo


I hate to hijack this thread but here is my question to Hondo or people that have experience with this setup... so you are running a two speed setup? 48 first then 96? but you mentioned that you have resistors... can you elaborate? what did you use as resistor? Does it give you a big jolt from 0 to the first resistor? what about the 1st to 2nd resistor?


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## hondo (Mar 30, 2009)

EV59Rag

I will take some pictures tonight that will help explain it better. With the switch, you can operate at 48 or 96 volts. I actually only have 2 banks of resistors now, I forgot that I took out the first one that wasn't really needed. Here is how I typically drive. When I first press on the pedal my "make before break" switch turns on the first contactor that allows the current to go through both banks before going to the motor. It is not much of a jerk at all and is great for backing up. As I continue to press on the pedal, the 2nd contactor kicks in (while the first one is still on). Again I feel a small jerk and the power picks up. As I continue the 1st contactor shuts off. Press more and the 3rd contactor kicks in (while the 2nd is still on) and I have much more power as the motor is now basically direct with the batteries. At 48 volts it accelerates slowly and only has a top speed of around 45 mph. If I need more speed I switch to 96 volts and I have all the power I need. I've had it up to 80 and it was still climbing when I backed off. The resistors are simply made of heavy nichrome wire. I experimented with different lengths and put them in parallel before I got what I wanted. Be patient for the pictures, I will try to get them up tomorrow.

Hondo


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## hondo (Mar 30, 2009)

Attached are the pics of my set-up. I know it is crude, but it is an ongoing experiment with electric cars. #1213 shows the first set of resistors and two of the contactors. #1216 shows the series/parallel switch in 48 volt mode, #1217 in neutral and #1218 in 96 volt mode. #1219 shows the second set of resistors mounted where the heater core used to be.

OK, back to my experiment. I guess I was sold a junk controller. I wanted to check it out before I hooked up the by-pass contactor but nothing worked. Double checked my pot and it was fine. I don't know if I want to spend money for another controller that I might blow up so....
I just ordered 4 big IGBTs for a different experiment. If I don't burn the garage down, I'll post the results. Wish me luck.

Hondo


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## hondo (Mar 30, 2009)

OK I forgot to add the pictures. Now that I am trying to add them to this post I am having difficulties. I thought I could just copy & paste but evidently I can't. Can someone tell me the easiest way to get the pictures added?

Hondo


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## JRP3 (Mar 7, 2008)

You need to have them stored on a site then link to them, no direct storage here on this site. I use Photobucket.com


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## major (Apr 4, 2008)

JRP3 said:


> You need to have them stored on a site then link to them, no direct storage here on this site. I use Photobucket.com


If you have the image on your computer, you can attach it directly using the paperclip in the toolbar, about in the middle.


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## JRP3 (Mar 7, 2008)

major said:


> If you have the image on your computer, you can attach it directly using the paperclip in the toolbar, about in the middle.


Hmmm, the only paperclip I see is for "remove link". No, that's not a paperclip it's a "link" of course. So I don't see a paperclip. However, I do see an attachment button below the reply box.


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## JRP3 (Mar 7, 2008)

Ok, I do see a paperclip now. Sheesh I'm blind!


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## hondo (Mar 30, 2009)

OK we'll try again. These should be the 5 pictures I spoke about a few posts back.

Hondo


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## major (Apr 4, 2008)

hondo said:


> OK we'll try again. These should be the 5 pictures I spoke about a few posts back.
> 
> Hondo


Hi Hondo,

I admire your ingenuity. But you can see why the single box PWM controller is popular.

Regards,

major


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## hondo (Mar 30, 2009)

I admire your ingenuity. But you can see why the single box PWM controller is popular.

Yea,but I was trying to build it cheap. I only had $2500 in the whole car and $1200 of that was for a new set of batteries. I now enjoy the car so much that I want to make it better. PWM may be my nest step, I am very interested in Paul's homemade controller on the other forum. I am going to study it more thoroughly and possibly build one or shell out the bucks for a store bought one. Thanks for your input.

Hondo


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## EV59RAG (Oct 6, 2008)

Very good info Hondo. I might be doing a contactor/controller too and I will study your setup very closely. It might be a diff setup since Im going to do (might do) 6, 12, 24, 48 and 72... we will see what happens...

thanks for the info... im really worried about the jerk in between the taps, but we will see.


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