# Curtis controller acting weak



## rfengineers (Jun 2, 2008)

What kind of vehicle are you converting? What is the weight? 
36-Volts at 400 Amps is only 14.4kW (19 Horsepower). That is not a lot of power for a car.


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## frodus (Apr 12, 2008)

36V 400A for a car? thats 14,400W peak, not that great for a car.

You're probably suffering from battery sag, meaning, you're trying to suck 400A from those batteries at 100% PWM.... and it causes the battery voltage to sag lower and go into current limit.

Have you measured the amps going to the motor? coming from the batteries?

What batteries are you using?

Thats a really small controller... high amps, but not much power (volts times amps)


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## mrcshbs (Nov 25, 2008)

it's a GEO METRO, very small car... I am using a forklift 36V motor... when I connect the motor to the batteries, as a test.. the car has more power than the regular gas engine... but when I connect the controller and push the pot all the down (accelerating) it starts... but the motor doesn't turn fast at all... like 200 rpms... maybe... and it won't even push the car forward...

but when I by pass it, and connect the motor, man... WHOO! watch out!

I am using 12 batteries... deep cycle marine batteries... 36V, the motor will go up to 48V... it's rated at 36, but a friend of mine said I could use it (not all the time) at 48V and it woudn't harm it.

3 batteries connected in series, making 4 packs of 36V... 

12V - 150 ah each. 36V - 600 ah the whole thing... 

the motor reaches 5000 RPM when connected at 48V... I don't have much specs on it though, by my friend told me the max speed is about 8000.. I won't reach near as much... so I am not worried about that...

I thought I connected something wrong ot the I should use the A2 pole... but nothing... the controller was used on a forklift and should have a lot of torque.... but I don't know what's going on.

I went by a forlift repair shor nearby here.. and they tested the controller and said it's fine.

any ideas???

it's dark now, but tomorrow I will take some pics of the motor and controller and my whole setup and post it here... but any ideas would be really appreciate it.

do you think if I get a higher amp controller would solve the problem???

I have no means of testing the amps... the voltage is correct though... goes from 0 to 36.

how do I get this controller to put out 400 amps??? the max currect is 400... 

Thank you

Marcos.


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## frodus (Apr 12, 2008)

does the controller have adjustment pots on the side (under some set screws)?

Its possible the current is set low.

Realize, that the 400A is max, not continuous. Download the manual and see if there are some adjustments on the controller. If they said its good, it should be ok, it might just need tweaking.

It sounds like your batteries aren't the limiting factor.... they're not going to sag much with 4 in parallel, 3 in series.


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## elevatorguy (Jul 26, 2007)

If it is a Curtis that 400 amps is a 2 min rating then will drop to 275amps for a 5 min rating. you will not see 400 amps continuous.
If you hook it directly to the batteries, you could be pulling 1000 amps which your motor will not like for too long. 
My thought would be to run it at 48 volts and a higher current controller.
You don't need to connect the A2.


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## mrcshbs (Nov 25, 2008)

I check the acceleration and current.. they're set to max..

I have the PDF manual... this is my exact setup.. however, I don't need the reverse on the motor as it turned CCW (looking from the front).. that the way the engine was running.

when I lift the front wheels, I accelerate (using the controller) you can even stop the tired using my hands...

but again, when it's connected direclty to the batteries, it's nice and efficient.

I am posting a snapshot of the wiring I have.

Marcos.


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## mrcshbs (Nov 25, 2008)

Jerry,

thanks for the reply... is there any way to see the 400 amps even for a few seconds??? 

I don't have any way to measure the amps... do you think Radioshack would have a cheap model that I could measure high amps?

I am on a fix budget right now... 

my friend told me the motor would work fine on a 48V controller, however, do you think If I get a 72V would it work?

Thanks

Marcos.


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## elevatorguy (Jul 26, 2007)

You should be able to get 400 or so for a while, curtis says 2 min. that should be enough to get you rolling. You could go to 72 volts but you would probably have to advance the brushes to keep your motor from arcing at the brushes at higher rpm. 
You can get a clamp on DC ammeter for 100.00 or so maybe less used.
Most only go to 400A or so, unless you spend more.
Are your wires large enough? is anything heating up?
It is very difficult to figure out the problem from a distance.
I think one of the other posts was correct, you have probably 2100 pounds of vehicle and a max of 19 hp best case. If you went 48 volt 600 Amps you could just about double avail power.


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## rctous (Jun 18, 2008)

have you looked to see that the pot box is putting out 5K ohms??????????????


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## mrcshbs (Nov 25, 2008)

yes, I bought the pot box from curtis, its a PB-6 or PB6 is I am not mistaken... it was designed for that controller... I also had it tested at the forklift repair shop...

what I am going to try to do is get a higher voltage controller...

one the things Jerry mentioned was the wires.. they were not heating up.. I think they are 4 Gauge wires... but i am getting something larger tomorrow... so I will probably go with 2 Gauge wires.

even though they are not heating up.

since the motor is rated at 36V, do you guys think if I get a 72V - 200 amps controller will it solve problem??

I will arrange the batteries from 36V to 72V.

also, does the contactor or precharge resistor makes any difference??? I mean, for testing purposes only if you connect the battery cables directly to the controller, will it change the performance or damage the controller?

question:

we know the motor is 36V, what would you say it's the best choice:

Option 1: get a 48V controller 600 amps
Option 2: get a 72V controller 400 amps?

what option would be the best for the 36V motor I have? what option would give be better power consuption/range etc.?

Thanks again

Marcos.


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## elevatorguy (Jul 26, 2007)

Higher current= better accelleration, higher voltage=better top speed. 
Advantages of higher voltage are ability to use smaller wiring.
Even if you are testing, precharge the controller with a resistor or light bulb.
make sure you have the wheels off the ground and or a way to quickly disconnect power if there is trouble.


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## major (Apr 4, 2008)

mrcshbs said:


> I am using a PM motor with only 2 poles... also, doesn't matter if I change the polarity, the rotation is always the same,


Hi mrcshbs,

Chances are this is a wound field motor, not permanent magnet (PM). When you say "poles", do you mean terminals?

Regards,

major


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## mrcshbs (Nov 25, 2008)

sorry, yes... there are only 2 terminals in the motor. I am posting some pictures right now.

thanks

Marcos.


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## mrcshbs (Nov 25, 2008)

ok.... here is a interesting note..

when the motor is connected to the controller, I turn the pot box, it goes from o to 36 volts... motor turn, however, there is no load..

when the motor is connected to the transmission, I turn the pox box and goes from 0 to about 7 volts... and the motor feels "weak"... it's like it's not nearly as powerful.

any ideas?

Marcos.

here are some pics.


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## My Dog Buddy (Jun 25, 2008)

Are you using an automatic transmission sure looks like it? That might explain why you can stop the wheels with your hands as well as some of the lack of power.


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## TheSGC (Nov 15, 2007)

mrcshbs said:


> ok.... here is a interesting note..
> 
> when the motor is connected to the controller, I turn the pot box, it goes from o to 36 volts... motor turn, however, there is no load..
> 
> ...


That looks much more like a Series Wound motor than a PM. Do the connections have any labels on them?


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## mrcshbs (Nov 25, 2008)

yes... it's an automatic transmission, however... that's all I got to work with... I wanted to do a manual tranny.. but couldn't find one on my price range 

so I decided to go with the auto... (car was 100 bucks 

about the lack of power, like I said, the car takes off like a maniac directly connected... without a controller, but again, when the controller comes in... it won't even more the car.

so, I connected the motor to the flywheel, I made an adapter from the flywheel to the torque converter.. it's beautiful... car is very silent.

the terminals on the motor have no label... it's also not reversable.. I connected the positive and negative, then reverse it... it only rotates same direction.

do you think a higher current controller will solve the problem???

also, found a controller 850 amps/48V for the same price as 72V 400 amps... do you think if I buy the 72V I will end up with the same dilema? (lack of power)

the tranny was also modified by of my my friends.. it's locked in 3rd grear and has a 12V pump keeping the pressure up... the pump runs off a battery (12V) I left it on to see how long it held up... it was about 5 hours... to dischage the batt...

any ideas?

Thanks

Marcos.


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## TheSGC (Nov 15, 2007)

I too have an auto tranny and it works fine. I don't have an external pump, I just give it a slow start until the gear engages, then I drive off. Takes the same amount of time to start driving as my Civic with a manual transmission (ICE).

You really should go for the 72 volts. Another possibility is that controller is speed limiting you since it may have been for a forklift and was modified to keep the speed low.


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## mrcshbs (Nov 25, 2008)

could be...

the motor is rated at 8000 rpm... but when the motor has no load and it's connected to the controller, it will reach that speed easily... but once the load is applied (once the motor is connected to the transmission) rotates at about 200 rpm... even with full throttle applied...

do you think if I spend the money with the 72V controller, will this still happen?

I mean, I am lacking amps going to the motor I guess.. once the motor is connected and load is applied, I check with the voltmeter on the motor terminals, it reads 7 volts... now if I take the motor out and run it with no load, it reads the full 36V.

what's going on???

have you guys came accross anything like that before?

OMG!! I have the whole thing ready to go.. this is the only thing.

please help.

Marcos.


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## elevatorguy (Jul 26, 2007)

You need to measure and find where the 29 volts are dropping under load. If your battery voltage before the controller is staying at 36 volts and you have 7 at the motor your loss is (1) a bad connection (2) motor controller (3) contactor, if used. 
Are the batteries fully charged, controllers have a low voltage cutoff.
you should have over 36volts fully charged. and when you load the batteries they should only drop a few volts.
How did they test the controller? with a load or without?


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## mrcshbs (Nov 25, 2008)

they tested the controller by putting it into a machine that does read outs..

they plugged all the controller terminals into a machine and said on the screen "passed" in green letters.

the batts are charged, I have a 36V automatic charger, one correction on the battery voltage, it reads 37.1 ... I haven't measured the batt voltage when the controller is connected and full throttle is applied.

I will do that tonight and post it soon.

thanks

Marcos.


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## mrcshbs (Nov 25, 2008)

Jerry,

about the controller, since the motor will run up to 72V, I saw a 48V 850 amp controller for the same price as the 72V 400 amps. do you think if I get the 72V controller will solve the problem? will I have a enough power to turn that transmission with same amps but higher voltage?

or do you think I should stick with the 850 amps, but lower voltages?

let me know what you think.

thanks

Marcos.


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## major (Apr 4, 2008)

mrcshbs said:


> I mean, I am lacking amps going to the motor I guess.. once the motor is connected and load is applied, I check with the voltmeter on the motor terminals, it reads 7 volts... now if I take the motor out and run it with no load, it reads the full 36V.
> Marcos.


 
Hey Marcos,

I'd be careful about running the motor no-load. It is advisable to use only 12 volts at no-load. Putting full 36 volts to the motor at no-load may cause overspeed damage.



> the motor is rated at 8000 rpm... but when the motor has no load and it's connected to the controller, it will reach that speed easily... but once the load is applied (once the motor is connected to the transmission) rotates at about 200 rpm... even with full throttle applied...


I think you need to measure motor current (amps) when doing these tests. It may be that, when connected to the tranny, the controller is in current limit, holding the motor voltage to 7 and RPM to 200.

Also, wondering why you locked tranny into 3rd. First would have been a better choice, at least for starters. And what are your plans for reverse?

I wouldn't spring for another controller until you figure out this one. An ammeter would be money wiser spent.

Regards,

major


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## grayballs (Aug 27, 2008)

mrcshbs said:


> Jerry,
> 
> about the controller, since the motor will run up to 72V,
> 
> Marcos.


I have yet to try anything less than 72v on a vehicle of over 800#. IMO, it just doesn't make sense, although I"m quite certain there are those that will argue the point. I agree with the post that asks you to check connections, contactors, controller, etc. It is always a critical point to insure proper torque on connectors,,,, even more critical at low voltages. I suspect you will find your problem there.
I have a few Curtis 1209 B 6402 controllers, (for series wound motors) that I have acquired through the years. If you decide to move up to 72v, drop me a PM and I'm sure we can work something out, without breaking the bank.


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## frodus (Apr 12, 2008)

methinks that you need at least a 20kw controller for what you're trying to do. Whats the GVR of the vehicle?

Even at 72V you're going to want over 400A for the vehicle to be of any use to you. The corbin sparrow is 156V and light, and can draw over 450A under heavy acceleration. My motorcycle running at 72V pulls 350A on the motor side, 150A on the battery side... and its 400lbs. I've had it pull 400A.

IMHO, 72V is way too low, and 400A at 36V is 14,400W max, and top speed is going to be very low, acceleration is going to leave more to be desired.

I think you're hitting current limit of the controller... its not a light vehicle.

You really need to get a clamp type current meter, and keep it with you at all times. They're about 100bucks for a decent DC current meter. 

Also 3rd gear is NOT a good gear to test in. most EV's start out in 2nd or 1st. You're not using a very high power level, and need to start out lower than other vehicles to get decent acceleration.

My bet is that you're actually pulling 400A in 3rd gear, and the motor is pushing more than 40-50ftlbs, but its in too high of a gear for it to move the 2500lb+ vehicle. Thats a pretty SMALL 6.7" motor. Looks like an Advanced DC series wound that is wired for one direction internally. How long is it?


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## mrcshbs (Nov 25, 2008)

here are some new pics of the whe motor...

I don't know exacly what motor it is... but I measured today.

thanks

what is the highest amp for 72V controllers?

anyone?

thanks

Marcos.


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## grayballs (Aug 27, 2008)

mrcshbs said:


> here are some new pics of the whe motor...
> 
> I don't know exacly what motor it is... but I measured today.
> 
> Marcos.


'Looks like a 6.7" ADC motor. They generally run in the 6 - 8hp (continuous) range at 72v. I think ADC's specs on the 4003 call for 15 hp, for 2 min, or something like that,,, one of the reasons that Curtis backs off the max amp outputs in short order.


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## ngrimm (Oct 19, 2007)

Another way to measure the amperage would be to measure the milivolt drop across a shunt that is connected in series with the load. The following article shows how to build a 800 amp diy shunt from a stainless steel bolt. http://www.fieldlines.com/story/2007/1/11/21434/1866


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## mrcshbs (Nov 25, 2008)

Hey guys,

please, before I burn my controller, let me know is this is possible.

can I put 2 controllers (same model #, same amps) connected together... what I mean is, connect ON BOTH the B+ to battery and motor terminal, then connect the M- on the other terminal, then the B- on bat neg.

and split the pot box wires and put in the 2 controllers at the same time? so they will both receive the same resistance and hopefuly send juice to the motor.

is this possible?

please let me know

Marcos.


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## elevatorguy (Jul 26, 2007)

Don't do that You will be buying new parts after the smoke clears.
Unless the controllers are controlled by a common driver circuit the differences in the controllers will not allow them to work in parallel


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## mrcshbs (Nov 25, 2008)

Jerry,

what exacly would I have to do to put these 2 controllers to work together... I mean, I would like to share the same pot-box with the 2 controllers.

let me know

thanks

Marcos.


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## TheSGC (Nov 15, 2007)

mrcshbs said:


> Jerry,
> 
> what exacly would I have to do to put these 2 controllers to work together... I mean, I would like to share the same pot-box with the 2 controllers.
> 
> ...


That's the thing, you don't. Controllers cannot function properly together, and if you managed to connect them together, the motor will not operate because it would be getting two different PWM signals and probably lock full on.


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## frodus (Apr 12, 2008)

mrcshbs said:


> Jerry,
> 
> what exacly would I have to do to put these 2 controllers to work together... I mean, I would like to share the same pot-box with the 2 controllers.
> 
> ...


You can't do it. Period. The FET's have to ALL turn on at the same time for it to work, and the two controllers cannot be sync'd.... with all the controllers that are out there right now. Its too hard to do in seperate controllers.

You should really start saving up. The controller is underpowered, and you'd need a 72V 400-500A controller to really move it like you want.

I'd stop trying to think too much ahead, and see what amps you're drawing now. Measure with a shunt, or a current meter. Until you know what the motor is drawing, or what the batteries are supplying, you're shooting in the dark.

Sure, you could get a larger controller, larger motor, and be good to go, but you still need to see what the current draw is.

What is the Gross vehicle weight?

Also, change it back to 1st gear, you shouldn't be starting in 3rd with that small of a motor.

With that motor and that controller it'l never be too peppy.


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## mrcshbs (Nov 25, 2008)

that's very good advice... and you're right... I think the controller is too small...

I will see if I can find a 72V controller with at least 600 amps. I have to save up for that a lot though.

Marcos.


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## frodus (Apr 12, 2008)

mrcshbs said:


> that's very good advice... and you're right... I think the controller is too small...
> 
> I will see if I can find a 72V controller with at least 600 amps. I have to save up for that a lot though.
> 
> Marcos.


two things here.... 

Why do you THINK you NEED 600A? That motor can't handle more than 4 or 500... its going to cook! You need higher POWER, as in watts as in volts times amps. 72V and 400A or so, is 28,800W peak.... twice what you've got now. Also, I seriously DOUBT you'll do 600A before the batteries sag and the controller goes into current limit. How did you go about "designing" this system? Did you buy a bunch of parts and throw it in hoping it'd work?

Second, you'll have a hard time finding a controller "at least 600A" right now. Kelly makes one, but people have had problems with them failing and being underpowered. Curtis, alltrax make controllers that are 400-500A. 72V is on the bare minimum-almost-not-enough range of the spectrum for an EV, especially for a conversion that wasn't designed to be light to begin with.

What is your vehicle weight right now? You haven't answered that.

Put it into 1st gear and try it... you may be pleasantly suprised.


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## grayballs (Aug 27, 2008)

frodus said:


> two things here....
> 
> Why do you THINK you NEED 600A? That motor can't handle more than 4 or 500... its going to cook!


POOF!! or SIZZLE & SMOKE


72v - 400a 28,800 watts = 38+ hp. Even that is asking a lot from a motor that is designed for 6 - 8 hp cont. Fortunately the Curtis 72v, 400a controller won't parcel it out at that level for more than a couple of minutes.
I have used the 4003 series ADC motor (72v 400a) on 2 Tadpoles and found it adequate. They were 800+ pound vehicles. I'm in the process of building a 2 wheeler with the same motor - controller package and some hacked prius cells. I'm hoping for more than adequate.
I'm guessing that the Geo platform is 2000# ? I think Frodus is right,,,Try 1st gear and hope for surprises.
So far, it sounds like you've done some inexpensive research, and that is never a bad thing


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## ww321q (Mar 28, 2008)

mrcshbs you have a problem some where that we can't see . 36 volts and a couple hundred amps will move a golf cart it should also move a car to , just not quite as fast . I didn't see but exactly what controller you are using ? I'm also wondering did you lock the trany in 3rd gear or a lower gear like 2nd . If it's in 3rd then the amp draw taking off would be very high and the controller would limit that . Using a low voltage system you may even need to use 1st to get the car moving at a lower amp draw then let it shift to 2nd to try to get more speed . Try to find out what the problem is . Don't just start throwing money at it trying to solve it that way . J.W.


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## major (Apr 4, 2008)

mrcshbs said:


> can I put 2 controllers (same model #, same amps) connected together... what I mean is, connect ON BOTH the B+ to battery and motor terminal, then connect the M- on the other terminal, then the B- on bat neg.


 
No. Well, maybe. But you'd have to put large inductors in the output circuits for each. Not a practical solution.

major


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## mrcshbs (Nov 25, 2008)

hey guys thanks for the inputs... I am very new (as you can see) on this EV thing.. but I the further I go with this, the more I want to learn.

the curb weight is about 2500 lbs... + or -...

and yes, I didn't do much planing, I started out reading stuff, and thought I could do one on my own... but it's been 6 months now and still working on it.

I have put the car in first gear and still won't move it... with the wheels OFF THE GROUND, when I use the controller, the wheels will move at about 10 rpm.. tops.. but when I lower the car, to the ground and apply full throttle, the car won't move.

I wasn't really planning to get up to 60 or anythign like that, I was thinking more like 30 mph tops.

I guess I should get a new motor uh?

do you think this motor will push the car up to 30 mph?

Marcos.


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## grayballs (Aug 27, 2008)

mrcshbs said:


> I have put the car in first gear and still won't move it... with the wheels OFF THE GROUND, when I use the controller, the wheels will move at about 10 rpm.. tops.. but when I lower the car, to the ground and apply full throttle, the car won't move.


With more information coming to light, I can't help but think there is more to the problem than motor/controller. If the controller is "current limiting" bolted tothe transmission with the wheels off the ground, I think I would revisit the tramsmission. That motor might struggle to move a 2000#-2500# car at any real rate but it shouldn't have that issue with the wheels off the ground. 
72v - 400a is probably a more practical power source but not the answer until you have ruled out the other possible problems.


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## frodus (Apr 12, 2008)

measure the amps into the motor, and amps from the batteries.... you need to know how many amps its drawing. Without that, you're not going to know what controller or motor you need to upgrade too. It might be a faulty controller.


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