# 1231C Curtis Controller - Jerking problem



## Tom W (Jun 9, 2008)

This problem was mentioned in another thread and I think a new thread on this subject might be appropriate.
I have almost 2000 miles on my Ranger and this problem occured on the first test drive and intermittently but daily since then. It feels like a miss in an ICE. It will "miss" when accelerating at 300 to 500 amps. This will happen anytime but more frequently when the SOC is 50% or less. I have checked all the terminals for tightness. EVA suggested a dirty spot on the pot but I don't think it is this as it does not occur at a specific spot. I think it is in the controller because when I have the AM radio on I can hear the frequency change when this happens.
Does anyone else have this problem or have any input?
This has not been a big problem and I am quite happy with the performance so far.


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## CPLTECH (Sep 14, 2007)

From your description that it happens at high amp draw and when batteries are at lower SOC, sounds as if the battery voltage drops low enough that the controller shuts down at those times. The Curtis manual says the “under voltage cutback” occurs at 43V on the 72-120V unit, 64V for the 144V unit. My take is that you ask a lot of the battery when you demand 300-500A. Even the big 6V Trojan or USBatt T145’s are rated at ~250AH, therefore exceeding that (except for brief moments) tends to warp the plates and reduce life cycles and the voltage drastically.
Another possibility is poor wiring connections that do not hold up during high amp draw, again reducing the pack voltage. 
What does your voltmeter look like at those times?
Just my first impressions…


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## Tom W (Jun 9, 2008)

Thanks for the reply. What you say sounds reasonable. I can't say for sure but I don't think the volt meter ever gets near 100V. I'll try to watch carefully but won't get a chance until after the 1st.

Merry Christmas to all.
Tom


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## los picos (Apr 2, 2008)

I believe the curtis 1231C had a problem with jerkiness due to large inductance motors if you are using 9" or larger. They resolved it with a frequency change for slow speeds, however, a depleted battery with increased internal resistance through age or misuse (drawing too much current repeatedly) will probably bring symptoms back. If you require top performance in 400+ amp bracket more than once a year, suggest an upgrade to a more heavy duty controller and offset the cost by selling the Curtis while it's still operational.


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## tj4fa (May 25, 2008)

los picos said:


> I believe the curtis 1231C had a problem with jerkiness due to large inductance motors if you are using 9" or larger. They resolved it with a frequency change for slow speeds, however, a depleted battery with increased internal resistance through age or misuse (drawing too much current repeatedly) will probably bring symptoms back. If you require top performance in 400+ amp bracket more than once a year, suggest an upgrade to a more heavy duty controller and offset the cost by selling the Curtis while it's still operational.


I'm having the same problem with the jerkiness when demanding more amps on heavy acceleration (300-500 amps) and while running with some demand in the 150 to 250 amp range. 

I did notice the AM radio whine at initial take-off when the controller normally starts up but never thought to listen in and see if it was audible at other times. Next time out, I'm going to "tune in" to AM to see if I can hear any whine at higher speed ranges.

Like in the post above, I'm thinking the pulse frequency might be too low for the larger motor ADC 9" motor and my heavier vehicle especially when some of the battery voltage has started dropping off a bit however I have never taken my batteries down to less than 50% DOD.

I've recently read EVs have exhibited driveline vibrations issues (judder, shunt, and clonk) more noticeable in the lower frequency range due to the high torque of electric motors and other things that may contribute to driveline vibrations more so than on regular ICE systems.

Things likely to contribute more vibration that are felt on EVs are things like our clutchless/direct drive systems, stiffer suspensions, higher inflation of tires, lack of a fluid medium found in automatic transmissions that help absorb vibrations, ect. 

I'm thinking of giving Curtis a call and see if they have any comments concerning this problem and get thier comments/recommendations. Before ditching the controller, I'm inclined to see if they think I should make adjustments from the stock settings of the current limit adjustment and accelation rate adjustment found on the controller.


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## madderscience (Jun 28, 2008)

For what it is worth, I have NOT noticed any such jerkiness with my 1231C and 9" motor. There is some drivetrain windup at low speeds with a fresh battery, but the problem goes away entirely once I am doing 10+mph, and I blame the high torque of the motor winding up my overstressed driveshafts for this. When this happens I just step on it more and the problem goes away.

At the highest battery amp draws I ever get to (300-400amps) there is no sign of the behavior described earlier in my car. My 126V battery (trojan T-105s) probably sags to 90-100v or so under this load when the battery is freshly charged.

Some other things which might be causing this jerkiness:

The motor commutator could be arcing over under high current / high voltage load, in effect shorting out the controller output. check your commutator SOON and do something about it if it shows signs of flashover or you could wreck your motor. This is most likely to be suspect if you have a lower voltage rated motor or a small motor relative to the size of your car, and you have not timed the brushes to handle higher loads/voltages. You could add an ammeter shunt on the motor side and see if the amps spike when this happens, that would be a dead giveaway that it was a motor problem and not a controller problem.

Is your 12V system losing power when your traction battery is under load enough that the main contactor or kill switch contactor is opening up? That could cause the behavior. You might be able to hear the clicking sound when it happens if there isn't enough other noise to mask it. This should be easy to diagnose too, because all your other lights/accessories would be very dim while the car was accelerating. My DC/DC starts losing output voltage when a lot of 12V accessories are turned on and I pull more than 150 amps or so off the battery so I know this can be a concern.

I like the potbox idea, but if it was the potbox you would probably observe the jerkiness at the same throttle position all the time.


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## rfengineers (Jun 2, 2008)

Tom W said:


> Thanks for the reply. What you say sounds reasonable. I can't say for sure but I don't think the volt meter ever gets near 100V. I'll try to watch carefully but won't get a chance until after the 1st.
> 
> Merry Christmas to all.
> Tom


If you can get your hands on one, use an analog meter instead of a digital one to take this reading. The analog meter will give you a better picture of brief and sudden drops in voltage. Most digital meters mask this type of behavior. 

Merry Christmas to you too!
Joe


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## Wirecutter (Jul 26, 2007)

madderscience said:


> I like the potbox idea, but if it was the potbox you would probably observe the jerkiness at the same throttle position all the time.


This is exactly the problem I've had, especially when first starting out. My vehicle did some scary lurching at very low throttle positions. I figured it was a dirty pot, and I deal with it (for now) by cycling the throttle a few times prior to powering up the vehicle. I doubt this workaround will last, though, and I'd like to eventually change over to a different kind of non-contact throttle. (hall? inductive?) I've seen guitar effect pedals that achieve this optically, with an "interrupter" having a wedge-shaped hole in it.

-Mark


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## Matt (Dec 29, 2008)

I am having a similar problem, its not all the time, but is happening more frequently. It seems to be related to load, and or throttle position, and has a smell associated with it. It happens usually after i shift to 3rd, and apply moderate throttle. I can back off the throttle, and it goes away, and my speed will increase, so it is not speed related. My batteries are fully charged, so I dont' think this is it, and the voltage doesnt seem to go down. It will happen in 2nd sometimes. It doesnt seem to be a specific throttle position, but is related to asking for acceleration. It is a Curtis 1231c with 150v system. It smells bad and jerks hard. Any ideas?

Also, thanks to rfengineers, who nailed the problem on the stuck contactor. I put in a disconnect switch and a 750 ohm, 25 watt resistor in parallel with the contactor, turn on the disconnect, wait about 15 seconds, then turn on the key. My contactor hasn't stuck again in about 15 trips. THANK YOU!

Matt


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## madderscience (Jun 28, 2008)

If you can smell something, then something is getting VERY HOT.

FIX THIS FAST before the problem gets worse.

look for loose battery cables, motor cables, controller terminals, bus bars, etc. and do it before you drive the car again. Signs of overheating are discoloration, melted insulation, black or grey metal that should be shiny, and evidence of arcing. 

If you can't find any cables that have this damage then it might be the controller having internal problems but most likely its a cable.

early on with my car I had a poor connection on one of my fuse brackets that made a hot ozone-like smell whenever I pulled more than 150 amps off the batteries for an extended period. Eventually I found it once it got bad enough that the fuse bracket started to melt down and deform.

As for your contactor, if it has been sticking at all it is a good idea to repair (if possible, just sand down the contacts lightly) or replace it as it is one of the safety power cutoff mechanisms in the car.

Good Luck


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## rfengineers (Jun 2, 2008)

Matt said:


> I am having a similar problem, its not all the time, but is happening more frequently. It seems to be related to load, and or throttle position, and has a smell associated with it. It happens usually after i shift to 3rd, and apply moderate throttle. I can back off the throttle, and it goes away, and my speed will increase, so it is not speed related. My batteries are fully charged, so I dont' think this is it, and the voltage doesnt seem to go down. It will happen in 2nd sometimes. It doesnt seem to be a specific throttle position, but is related to asking for acceleration. It is a Curtis 1231c with 150v system. It smells bad and jerks hard. Any ideas?
> 
> Also, thanks to rfengineers, who nailed the problem on the stuck contactor. I put in a disconnect switch and a 750 ohm, 25 watt resistor in parallel with the contactor, turn on the disconnect, wait about 15 seconds, then turn on the key. My contactor hasn't stuck again in about 15 trips. THANK YOU!
> 
> Matt


You're welcome Matt.

Madderscience is right about your overheating problem. This afternoon I ran my car up the highway for 12 miles at 65-to-70 mph, pulled over, popped the hood and checked the controller temperature. It was 105-degrees. The outside air temp was 80. All other connections and batteries were under 100-degrees. (A non-contact thermometer is a wonderful thing to have!)

Check all of your high-current connections and fix that problem!


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## tj4fa (May 25, 2008)

Matt said:


> I am having a similar problem, its not all the time, but is happening more frequently. *It seems to be related to load, and or throttle position, and has a smell associated with it. It happens usually after i shift to 3rd, and apply moderate throttle. I can back off the throttle, and it goes away, and my speed will increase, so it is not speed related.* My batteries are fully charged, so I dont' think this is it, and the voltage doesnt seem to go down. It will happen in 2nd sometimes. It doesnt seem to be a specific throttle position, but is related to asking for acceleration. It is a Curtis 1231c with 150v system. It smells bad and jerks hard. Any ideas?
> 
> Also, thanks to rfengineers, who nailed the problem on the stuck contactor. I put in a disconnect switch and a 750 ohm, 25 watt resistor in parallel with the contactor, turn on the disconnect, wait about 15 seconds, then turn on the key. My contactor hasn't stuck again in about 15 trips. THANK YOU!
> 
> Matt


You get to run in 3rd? I normally only drive around in 2nd up to at least 55-60mph. When I've gone up to 3rd, my amp gauge (shunt and gauge installed right before motor - after controller) shows more current being sent to the motor than at 2nd.

I've never been out on a long stretch (and probably flat or down an incline) to go past 60-65 to really use 3rd gear.

Could it be your motor is sucking more amps and heating up the windings because you may be shifting early? And when you back off the throttle, maybe the windings in the motor cools somewhat?

Siince I haven't got my tach hooked up yet and can't tell shift points by RPM, how fast (MPH) are you going when you shift to 3rd?


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## Matt (Dec 29, 2008)

Thanks for the reply, Madderscience. Cool website. I have just started one at mattselectriccar.com

I just drove it again before reading your reply. I had checked the connections, but will check again tonight.

It seems to be jerking more frequently now. I noticed a few other things...it is load dependent, 3rd gear worse, 2nd gear not as bad, 1st no issue...i watched the current draw and at times jumped as high as 400-500 amps at 40 mph in 3rd gear (stock beetle trans)

I went up a hill and kept the throttle in one position...nothing for a little while, then boom, boom, boom. Not exploding, just jerking. The amp draw seems to spike and definitely a smell. I didn't see any signs of arcing, but will look again.

Do you have any advice on gear selection while driving? It seems to shift smoother if I shift to 2nd at 15mph and 3rd at 20-25 mph. What is the most efficient route, or how do you determine that? 

I appreciate all your help. BTW, the contactor is still working great. I think it is sealed, so I dont know if I can sand the contacts...it is a Kilovac EV200.

Matt


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## Matt (Dec 29, 2008)

How do you know when to shift? I am shifting probably more for an ICE. I am shifting to 3rd at 20-25 mph, and I have noticed that higher amp draw in 3rd...sometimes as high as 400-500amps. 

Also, my kit did not come with a heat sink. How do I know if this is necessary? What temperature will create the problem? Where do I shoot the thermo at?

Thanks for the help.

Matt


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## tj4fa (May 25, 2008)

Matt,

Below is a link to be able to download a Curtis Manual for the 1231C controller in case you don't have it already.

I'm thinking you may be using too high a gear to try to drive in for an electric motor shifting at the low speeds you mentioned above. 

I recommend asking one of the VW guys like (Gottdi?) what gear they normally drive around in. This person uses 2nd to drive around in. See his comments on his EValbum site. http://www.evalbum.com/1466

http://www.cafeelectric.com/curtis/Curtis_manual.pdf

The manual will tell you what the controller cut-out is for overtemp/under-temp on page 40 where it will go into a type of limp mode.

I don't think you'll find anyone who doesn't run a heat sink or some sort of forced air/cooling onto the controller to keep it from over-heating (unless maybe they live in really cold climates).


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## Matt (Dec 29, 2008)

Thanks tj4fa,

I will try the driving style change tomorrow and see what happens. I'll also investigate a heat sink.

Thanks

Matt


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## tj4fa (May 25, 2008)

Matt said:


> Thanks tj4fa,
> 
> I will try the driving style change tomorrow and see what happens. I'll also investigate a heat sink.
> 
> ...


Or the smell could be your parking brake is still on...

Your welcome and hope I helped some...

Tomorrow, I'm going to re-bolt my driveshaft 180* and see if it helps getting rid of some of my vibration.


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## Matt (Dec 29, 2008)

OK, thanks for all the help with this jerking issue. Turns out, as you guys said, there was a loose connection, well uh, make that connections! I was focusing on the controller and contactor connections, and should have been looking closer at the battery connections...3 had come very loose. It was intermittent because I think it went along with hitting a bump, while under heavy load, ie sometimes it did it and sometimes not. Also, 2nd or 1st made it better due to less amp draw. 3rd exaggerated the issue.

So, if someone is noticing a severe jerking under moderate to heavy load, check ALL of your connections. If it seems to be getting worse, thats another good indication that something is continuing to loosen. 

Thanks for all your help guys...I broke my personal records today.
5 miles away from the house, one direction, was 3 miles
34 1/2 mile range, this is close to it I think
62 mph, in 2nd...I think I can hit 70 mph in 3rd

Matt


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