# Stuttering under load



## Dougnutz (Aug 22, 2011)

I’ve got several cycles on the new battery pack and my ev-grin is wide 
But last night I experienced some stuttering at higher rpm under accelerations. Somewhere around 3500-4000 rpm while accelerating the truck started jerking like the motor was cutting out. It seems to be somewhat intermittent but definitely repeatable. I did a quick search for other posts on the same issue but didn’t find much. 
I'll tear into it this weekend, check all the connections, etc. But I would appreciate any advice on things to look for.
warp9, curtis 1231c


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## PZigouras (Jun 5, 2010)

Was it a sag, like the controller is derating itself, or is it more like a harsh vibration? Keep in mind that the 1231c likes to have a massive heat sink with lots of fans, otherwise she can't dissapate the heat fast enough to run at full power.


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## Dougnutz (Aug 22, 2011)

It wasn't what I would call a violent vibration but some might. I would say it cycled hi/low power about twice a second. 

The controller has a pretty large heatsink (in my opinion). wider and longer than the controller itself with fins about 1 in deap. Plus 2 fans about 5in in dia. 

It seems like the only thing that could cause this would be either the controller or a bad connection.


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## EVfun (Mar 14, 2010)

It sounds like a bad pot box. When they get older sometimes the pot inside starts jumping the resistance value around. This is often first noticed in a section of travel that has seen frequently used, but sometimes happens at a random part of the travel. Usually you can cycle the throttle from off to full back and forth quickly several times (with the vehicle off) and get it to work a bit better for a while.


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## Dougnutz (Aug 22, 2011)

EVfun said:


> It sounds like a bad pot box...


Hmm that seems fairly likely. I bought this truck already converted and the FLA batteries that were in it were pretty much shot. So the throttle probably spent a lot of time at the high end of the range 

I get a dso on it and run it through the full range, if it has a bad spot it'll show.


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## Guest (Oct 14, 2011)

Sounds like a heat problem. Did you put a layer of thermal compound between the controller and sink? Are the sink and controller surfaces flat? It may be right on the edge of cutting out because of over heating. I agree that you might check the pot. If you got a cheap aftermarket PB-6 Like Pot then you may have a bad one. The real deal is much better quality. I'd suggest you use a 3 wire TPS rather than the PB-6 if you can. Made my life easier. Pots work but are subject to odd behavior from time to time if its a cheap one.


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## Dougnutz (Aug 22, 2011)

gottdi said:


> Sounds like a heat problem. Did you put a layer of thermal compound between the controller and sink? Are the sink and controller surfaces flat? It may be right on the edge of cutting out because of over heating. I agree that you might check the pot. If you got a cheap aftermarket PB-6 Like Pot then you may have a bad one. The real deal is much better quality. I'd suggest you use a 3 wire TPS rather than the PB-6 if you can. Made my life easier. Pots work but are subject to odd behavior from time to time if its a cheap one.


At a quick glance I can see thermal paste around the edges of the heat sync so I'm pretty sure the mating surfaces are in good shape. I'll pull them apart if I don't find anything else wrong.


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## Guest (Oct 14, 2011)

Dougnutz said:


> At a quick glance I can see thermal paste around the edges of the heat sync so I'm pretty sure the mating surfaces are in good shape. I'll pull them apart if I don't find anything else wrong.


If you see it I am sure your fine there. So your saying you did not to the thermal grease but someone else. Did you purchase a kit? From whom if yes? I purchased a converted EV with a real crappy kit and the heat sink was warped and the previous owner killed two controller post haste and I cooked one within a day after getting the car. It had already been hooked up. The warp in the sink was not visible until you put a straight edge to the sink. I am hoping that my sink is now good. It has been milled perfectly flat so should be fine now. I only ask because of prior experiences similar to yours. One controller I had did not have any sink and cut out right away. I then put on a large solid block but that soon got to hot and would not dissipate heat and got the same results. I then put on a good sink and high volume fan and the controller never ever went back into thermal cutback. The Kelly has not been tested yet with the flat sink. 

Pete


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## DavidDymaxion (Dec 1, 2008)

Once I had a stutter and it was brush arcing.


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## Guest (Oct 14, 2011)

That's good to know. Something to add to the collection of diagnostic checks. 

Thanks
Pete


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## gojo (Feb 1, 2011)

Dougnutz said:


> At a quick glance I can see thermal paste around the edges of the heat sync so I'm pretty sure the mating surfaces are in good shape. I'll pull them apart if I don't find anything else wrong.


The Curtis is supposed to drop down power if it gets hot to protect itself.

IR guns are great for keeping an eye on components. High heat usually means trouble. They don't cost much, and can be used for a lot of things; controllers, connections, wheels. 

They only cost about $50, and can easily pay for themselves. I found one of my wheels was running hotter then the rest. I ended up replacing a caliper, and I went from 2.5 to 2.6 amp hours per mile to 2.1 to 2.2. 

I used the IR gun on my Curtis 1231, and toyed with it until I got it to stay under 120F. I didn't use a heat sink. I used a fan in the front, and had space in the back for forward motion air to blow through.


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## Dougnutz (Aug 22, 2011)

gojo said:


> The Curtis is supposed to drop down power if it gets hot to protect itself.
> 
> IR guns are great for keeping an eye on components. High heat usually means trouble. They don't cost much, and can be used for a lot of things; controllers, connections, wheels.
> 
> ...


I do have heat gun already, so this would be an easy check. I just didn't think it would be the controller because it seems to switch too fast. But if it is right at the border of overheating maybe that would do it.


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## gojo (Feb 1, 2011)

Dougnutz said:


> I do have heat gun already, so this would be an easy check. I just didn't think it would be the controller because it seems to switch too fast. But if it is right at the border of overheating maybe that would do it.


You are correct. I am sorry for getting off from the OP. I am just promoting IR guns because I think they are a great EV tool. 

Getting back to your concern. When I first did my conversion, I was so sure I had all my connections tight, and it turned out I had two loose connections. A friend found one on my motor, and I found the other one after it melted half of a battery post. Not that I would limit you to something stupid I did, but just to say, I was sure all my connections were tight.


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## b2600ev (Jun 19, 2011)

Dougnutz said:


> But last night I experienced some stuttering at higher rpm under accelerations. Somewhere around 3500-4000 rpm while accelerating the truck started jerking like the motor was cutting out. It seems to be somewhat intermittent but definitely repeatable.


Wow, I could have written this post. I have the exact same issue. I have a mazda pickup, recently completed conversion, in service for about two weeks now. I have the Curtis 1231C-8601 and an ADC FB1-4001. This happens to me in second or third gear, only under a heavy load (full accel) and only within a very narrow RPM range. When it hits something a little below 4000 it jerks and stutters a bit, but as the rpm goes a little higher it stops and is again smooth. If I am not applying full power, this does not happen. I dont think it is the controller cutting out because for one thing my battery amps are showing around 400+A and not being reduced, and second because this happens first thing when I leave my office. There is a big hill right out my office driveway and this is when it happens, before there is a chance for anything to get warm.


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## Dougnutz (Aug 22, 2011)

b2600ev said:


> Wow, I could have written this post. I have the exact same issue. I have a mazda pickup, recently completed conversion, in service for about two weeks now. I have the Curtis 1231C-8601 and an ADC FB1-4001. This happens to me in second or third gear, only under a heavy load (full accel) and only within a very narrow RPM range. When it hits something a little below 4000 it jerks and stutters a bit, but as the rpm goes a little higher it stops and is again smooth. If I am not applying full power, this does not happen. I dont think it is the controller cutting out because for one thing my battery amps are showing around 400+A and not being reduced, and second because this happens first thing when I leave my office. There is a big hill right out my office driveway and this is when it happens, before there is a chance for anything to get warm.


Yea, your symptoms seem to be pretty much exactly the same as mine. I haven't made much progress trouble shooting mine lately as I have had the battery pack dissassembled for balancing. I'm planning to get it all put back together this weekend and see if the problem still exists. I tend to thing it will. Since I haven't found any bad connections or anything else that may explain the problem.


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