# Curtis 1231C-8601 not giving up the power



## gsmith191145 (May 1, 2011)

I have run into an issue with my controller. My ammeter reads 100 amps while I am driving. I noticed that my car is rather sluggish nowadays. Is this a mosfet problem? 

I am in the position where I can afford to have it rebuilt, but not replaced. 

I have little understanding of how the controller operates, but would like to fix it myself if possible.


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## Salty9 (Jul 13, 2009)

You can download a manual at http://www.thunderstruck-ev.com/Manuals/1231.pdf. Don't know if it will help.


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## madderscience (Jun 28, 2008)

how do you know it is the controller?

What is your nominal battery voltage, and what is it under the maximum load you can draw?

How old is the controller? batteries?

How good is the controller's cooling?

Got any loose/bad connections in the traction pack or motor wiring? How are the motor brushes?

My curtis 1231 is ~4 years or so old now. Still working exactly the same (boringly, but reliably) as when new. (knock on wood)


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## gsmith191145 (May 1, 2011)

madderscience said:


> how do you know it is the controller?
> 
> What is your nominal battery voltage, and what is it under the maximum load you can draw?
> 
> ...


My pack voltage is 120V.

The controller is almost ten years old.

The batteries are new as of 04/2011.

I have a pretty good heat sink on the controller and it is set up in the front grill of my car. 










My brushes are in excellent condition. I checked all my connections. My car was a production car and has two splices connecting the front and back battery packs. They could be an issue as well but I checked the current through them and they seem to be fine.


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## Taylorcarter (Oct 8, 2011)

Salty9 said:


> You can download a manual at http://www.thunderstruck-ev.com/Manuals/1231.pdf. Don't know if it will help.



Thanks mate for the PDF


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## brainzel (Jun 15, 2009)

My Curtis 1231C operates in the same amperage range (80-120A country road driving 50-60mph) with a comparable setup of passiv cooling.

Have you checked your potentiometer throttle? I had some issues because of humidity and temperature this summer ...


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## Tesseract (Sep 27, 2008)

gsmith191145 said:


> I have run into an issue with my controller. My ammeter reads 100 amps while I am driving. I noticed that my car is rather sluggish nowadays. Is this a mosfet problem?
> ...


You didn't specify whether you are measuring current on the battery side of the controller, or the motor, but I'm reasonably sure from your description that these are battery amps and battery amps are always lower than or equal to motor amps in a PWM motor controller. This is such a commonly asked question I added an appendix to the Soliton owner's manual to explain it.

The Curtis 1231C might be an obsolete and incredibly crude controller but it is generally quite reliable. However, like all PWM controllers, when it does fail it is almost always a spectacular event, and not a gradual decline in output power. The MOSFETs don't "weaken" as they age; they either work or they explode, there is no in-between state.

If your car has recently started feeling sluggish then the first place to look is the battery pack. The connections, the electrolyte level (if flooded), the state of charge of each cell (ie - use a hydrometer to measure the specific gravity), and especially, the temperature. Even here in Florida the temperature has dropped 10 degrees so I imagine it's a lot colder anywhere north of us. The colder the temperature the higher the internal resistance of pretty much every type of battery chemistry.


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## gsmith191145 (May 1, 2011)

brainzel said:


> My Curtis 1231C operates in the same amperage range (80-120A country road driving 50-60mph) with a comparable setup of passiv cooling.
> 
> Have you checked your potentiometer throttle? I had some issues because of humidity and temperature this summer ...


My controller operates about 100 amps on my ammeter from 0 to 60 miles per hour. It used to do 225 amps while accelerating. 

I changed throttle pot and contactor just recently.


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## gsmith191145 (May 1, 2011)

Tesseract said:


> You didn't specify whether you are measuring current on the battery side of the controller, or the motor, but I'm reasonably sure from your description that these are battery amps and battery amps are always lower than or equal to motor amps in a PWM motor controller. This is such a commonly asked question I added an appendix to the Soliton owner's manual to explain it.
> 
> The Curtis 1231C might be an obsolete and incredibly crude controller but it is generally quite reliable. However, like all PWM controllers, when it does fail it is almost always a spectacular event, and not a gradual decline in output power. The MOSFETs don't "weaken" as they age; they either work or they explode, there is no in-between state.
> 
> If your car has recently started feeling sluggish then the first place to look is the battery pack. The connections, the electrolyte level (if flooded), the state of charge of each cell (ie - use a hydrometer to measure the specific gravity), and especially, the temperature. Even here in Florida the temperature has dropped 10 degrees so I imagine it's a lot colder anywhere north of us. The colder the temperature the higher the internal resistance of pretty much every type of battery chemistry.


Thank you for the information. I got my amp draw from my ammeter. I did a voltage test that I found in the curtis manual. B+ to M- under load. I was supposed to see full pack voltage under load but on got 18 volts. I checked across B- and B+ and got full pack voltage.


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## gsmith191145 (May 1, 2011)

Salty9 said:


> You can download a manual at http://www.thunderstruck-ev.com/Manuals/1231.pdf. Don't know if it will help.


Thanks for the manual.


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## gsmith191145 (May 1, 2011)

Question: Is my controller wired correctly? 

When I got my car it had the controller in it. B+ B- and M- are hooked up. A2 is not used. 

There is a strap on my motor jumping two of the terminals. 

I am not 100 percent sure why.


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## Ziggythewiz (May 16, 2010)

If it's moving in the correct direction, it's hooked up right.

The jumper used selects CW or CCW rotation, and A2 is for plug braking, which is not used for road EVs.


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## gsmith191145 (May 1, 2011)

Ziggythewiz said:


> If it's moving in the correct direction, it's hooked up right.
> 
> The jumper used selects CW or CCW rotation, and A2 is for plug braking, which is not used for road EVs.


Thank you for that info.

I hooked up my volt meter to B+ and M- on my controller and monitored it while driving. 

I get a max voltage of 86.6 volts while accelerating and it cuts back to 75.2 volts in first gear, but picks back up to 80 volts going all the way to third gear. 

So my controller is getting 86 volts to the motor at any one time. 

Also I checked across B+ and B- while driving and I start out at 126VDC and while accelerating it goes to 115VDC. 

I cruise at 118VDC. 

I load tested my batteries and they tested good.


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## Coulomb (Apr 22, 2009)

gsmith191145 said:


> I have run into an issue with my controller. My ammeter reads 100 amps while I am driving. I noticed that my car is rather sluggish nowadays. Is this a mosfet problem?


Almost certainly not MOSFET. It may be the capacitors aging.

An Australian Curtis user had a similar sounding problem some months ago:

http://forums.aeva.asn.au/forums/forum_posts.asp?TID=2499

You seem to have checked all the other possibilities pretty well, as long as the pack doesn't sag much in voltage under load.

If you've checked that as well (I could well have missed where you told me), then I'd say a refurbishing of the controller could be called for.


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## Coulomb (Apr 22, 2009)

gsmith191145 said:


> Also I checked across B+ and B- while driving and I start out at 126VDC and while accelerating it goes to 115VDC.


Others with lead acid could chime in, but that sounds acceptable to me. So it is sounding like the controller to me.


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## Ziggythewiz (May 16, 2010)

Mine go from 130 to 110 for anything over 50% throttle.


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## gsmith191145 (May 1, 2011)

Thank you for the information. I will send my controller in for repair. I will post what the verdict is once it is returned to me.


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## EVfun (Mar 14, 2010)

Have you checked to verify the throttle pot box is going to at least 4500 ohms when the throttle is wide open? The pot is the lest reliable part of the controller package. The voltages you saw would be about right if full throttle inside the car was only 3400 ohms at the pot box.


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## Ziggythewiz (May 16, 2010)

Good point. Be aware the controller's internal resistance will affect your measurement, so pull the pot pins off the curtis and hook your meter to them before flexing the range on the pot.

Also, while you're back there get a helper to hit the pedal for you to make sure you get the same range (or close to it) as by hand.


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## gsmith191145 (May 1, 2011)

EVfun said:


> Have you checked to verify the throttle pot box is going to at least 4500 ohms when the throttle is wide open? The pot is the lest reliable part of the controller package. The voltages you saw would be about right if full throttle inside the car was only 3400 ohms at the pot box.


I ohm tested my pot it was putting out 4200 ohms. I adjusted it and it went to 4680 ohms max. 

Still did not see improvement though. Anyone recommend a better pot box?


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## EVfun (Mar 14, 2010)

It sounds like you have fixed the pot problem. Please be sure the max position is over 4500 ohms when the throttle is pressed inside the car, not when you move the lever by hand. If you have at least 4500 ohms, but not over 5500 ohms, the pot box is giving the full throttle command. The other problem a pot box may develop is jerkiness where the resistance increase is no longer smooth and even as the throttle is pressed. If you have neither I recommend you leave the thing along until it does cause problems. Some last nearly forever, others are trouble every couple years. That is why I keep my old PB-10 box that was built in the late '90's -- it just works.


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## gsmith191145 (May 1, 2011)

I had my controller rebuilt/replaced through cloud electric for 800.00. 

They sent me a rebuilt unit. 

I must say that I did not remember my car driving so fast. I must have just not realized how good life was when it was new. 

Just FYI for everyone, this was a great deal. 

Thank you for all your entries.


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## EVfun (Mar 14, 2010)

Thanks for the update. Glad to see you have fixed the problem. I haven't seen an old Curtis not giving full power. The usual complaint is that they blow up after being abused to many times. I sent flames 2 feet out the end of a Curtis 1221 -- it was no longer rebuildable.


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