# Broken curtis 1231c!!!!!!!



## Salty9 (Jul 13, 2009)

Have you checked?

http://www.paulandsabrinasevstuff.com/store/page3.html

Jack Bauer and JimDear2 have built them.


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## lou-ace (Jul 21, 2009)

interisting link Salty, but I'm not yet ready to build a new controller I just want to fix the one I have, I'm hoping for warrantee work from curtis as the seals are intact, but in true DIY fashon I may consider repairing it my self I have beginning to moderate electronic technical ability some trouble shooting, soldering, component replacement skills, but no engineer or design ability, in other words I can do simple fixes and break the rest........... thanks.


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## lou-ace (Jul 21, 2009)

*Re: Broken curtis 1231c!!!!!!!'d*

well,well,well someone pm'd me with the info that the KSI lead needs to be ralayed through the pack voltage. WOW I had it previously attached to the switched accesory 12 volt system. The owners manual states that the controller will turn on with any voltage greater than 8v. So I assumed that it would run on the 12v system and it did untill this problem. Now It does seem like that it is just not turning on. I wonder why It ran in the first place wired the way I had it? Is the casing isolated ( electrically) and somehow it could find a ground and therefore would turn on when switched, and somehow lost that ground and that is why it's not running now? So I'm now anxious to reattach it and wire the KSI lead to the pack as the schematic dictates. I will repost here with my results. On that note why do I need another relay for the pack voltage? why cant I tap a lead from the down side of the microswitch/relayed albright contactor that runns the drive power curcuit? initially I'll try that for a test. wish me luck.


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## Guest (May 4, 2011)

*Re: Broken curtis 1231c!!!!!!!'d*

Is your 12 volt accessory sagging below 8 volts? Could it be that it just shut off because of low voltage? Use a DC DC to power the controller. It takes pack voltage and puts in a clean 13.4 volts or so to your controller. Even if the pack goes low the DC DC should still provide a clean 13 volts to the controller. Keeping it alive and well. Check that first. Check to see if you are getting 12v to the controller. Do all the easy stuff first. Fuses? I put in a vicor mega pack and used the standard 15 output to use for my accessory power for the cars voltage and for the controllers voltage. Well the controller just quit working. Came to find out that the controller does not like any thing above 14.8 volts and wont run. Lower the voltage to 14.6 and it's a happy camper. Check those voltages in. I would not use full pack voltage. The controller can work just fine with 12 volts so use that but use it from a DC DC instead of your lead acid accessory battery. Those can drop in voltage easy and things just quit working but are not bad. Usually a controller will smoke out if it dies but I am sure not always. So I'd check those little issues first that you normally don't even think about. 

Pete


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## EVfun (Mar 14, 2010)

*Re: Broken curtis 1231c!!!!!!!'d*

The Curtis 1231C doesn't use vehicle 12 volt power for any purpose. The terminals on the front look like my 1221B. There are 4 bus bars (one is for plug braking and generally not used) and 3 small terminals. 2 of the small terminals are for the pot box and the other one (ksi) is connected to pack positive to turn on the controller. Here is a pdf of the manual. What you describe sounds like a common failure action. These controllers have an analog control board powered by the pack voltage (through the ksi pin.)


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## Guest (May 4, 2011)

*Re: Broken curtis 1231c!!!!!!!'d*

The pot box and ksi switch can run from 8 on up. Do you really need full pack voltage? I never used full pack voltage on any of my controllers for the pot and ksi switch. You can use DC DC power if your controller will run on that voltage. Pretty common actually. I think curtis is about the only one that uses full pack power. Kelly tried that in the beginning and then went to a lower power. Less failures. My old GolfTech used 12 volt dc dc and would run from 8 volts to like 28 for the ksi and pot. 

Pete 

Check your power to your KSI and be sure it is not below the low limit. It will shut you down on the spot.


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## Guest (May 4, 2011)

*Re: Broken curtis 1231c!!!!!!!'d*

The controller KSI is used to turn the controller on and off. KSI is turned on by connecting it to battery B+. *Any* positive voltage greater than about 8 volts will turn on the controller, but usually the full vehicle battery voltage is used.


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## EVfun (Mar 14, 2010)

*Re: Broken curtis 1231c!!!!!!!'d*

If you connect your Curtis ksi terminal to +12 volts from the vehicles 12 volt system you just un-isolated your traction pack. Figure 8 on page 9 of the manual shows ksi connected to pack voltage. I have always connected it as shown, except for not using a pot box with a microswitch and never connecting A2. I use a light bulb with the standard E27 base for the precharge resistor.


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## lou-ace (Jul 21, 2009)

well the good news guys is my controller isn't broken, after hooking it up with the KSI to pack voltage it works marvelously!! After some review I think I have to agree with Evfun. When I mistakingly wired the KSI to the accesory 12 v system I was bothered by the fact that I only used one lead ( the hot 12v accesory lead), and that there was no obvious ground for this circuit, electronics 101 always dictates that you have a positive lead and a ground for a complete circuit, here I assumed that the chassis of the controller was that ground, but In reality I think that the controller and pack circuit is supposed to float ,always, therefore it only follows that the ground leg for the KSI should be interlnally connected to the pack within the controller maintaining that "floating" posture, and its switching circuit would be reguired to come from the same source, i.e. the pack, any other arangement sacrifices the " floating"aspect of the pack design. I posted a forum earlier where I was trying to solve a "surging" problem that I was having with the truck, that totally resolved with the proper wiring. furthermore, I have a much beter performance profile now, smooth/seamless acceleration, and I believe that I actually have more power at lower current draw! WOW Its like a whole different controller. I now think that when I hooked up the KSI to the accesory side, I created a loose ground in the chassis of the controller, that was unstable, hence the surging I was previously encountering, this was probably caused by the controllers on/off swicth trying to find ground/ shorting/ turning on-off and just plain being unstable. I dont know why It worked for 5 months that way or why It finally failed to turn on but I'm glad it did and that i've got it wired properly, and I'm frankly greatfull that I didn't blow it up or cause a fire, or fry myself thats my take thanks again all.........


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## Guest (May 5, 2011)

*Re: Broken curtis 1231c!!!!!!!'d*



EVfun said:


> If you connect your Curtis ksi terminal to +12 volts from the vehicles 12 volt system you just un-isolated your traction pack. Figure 8 on page 9 of the manual shows ksi connected to pack voltage. I have always connected it as shown, except for not using a pot box with a microswitch and never connecting A2. I use a light bulb with the standard E27 base for the precharge resistor.


My above post was taken directly from the manual you linked to so yes you can use any 12+ source but you need to be sure it remains above 8 volts which I believe was the problem. He had a weak accessory battery and did not use an isolated DC DC for the controller voltage. As long as your controller can take in full pack voltage then there is no reason not to use it. I only mention because it is stated in the manual and that many other controllers do not use full pack voltage but use DC DC accessory voltage to power the controller. 

Pete


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## Ziggythewiz (May 16, 2010)

According to the Curtis manual, 1231c should be pack voltage via KSI relay, and 1221 should be 12V via KSI only.


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## Guest (May 5, 2011)

> KSI Wiring
> The keyswitch input (KSI) circuit includes inputs from the keyswitch and from the various interlocks. The controller KSI is used to turn the controller on and off. KSI is turned on by connecting it to battery B+. Any positive voltage greater than about 8 volts will turn on the controller, but usually the full vehicle battery voltage is used.


Taken directly from the Curtis 1231c manual. Can't argue with that now can you!


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## Ziggythewiz (May 16, 2010)

Any idea why Curtis says "usually the full vehicle battery voltage is used" but the typical wiring diagram for 1221 shows 12v? (Figure 7 IIRC)


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## EVfun (Mar 14, 2010)

Fig 7 shows a setup without a separate 12 volt system. This is common in forklifts and lower voltage installations. Fig 8 shows the setup with a 12 volt system that is isolated from the traction pack. This is the common setup with our on-road EVs. I used a Curtis 1221B controller for 11 years and always connected ksi to traction pack positive (+120 volts) through a relay.


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## Ziggythewiz (May 16, 2010)

Thanks for that clarification. I had overlooked that detail.


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## Guest (May 6, 2011)

My DC DC output is isolated. So I can use it to power the controller. I don't disagree but pointed it out. I also posted first because I was trying to trouble shoot the problem. Too bad he did not check to see if he had a low 12 volt battery that dropped below the minimum 8 volt threshold. Yes, he is good now but he needs to fuse that line with a small fuse. No need for more than like an amp fuse in that line. Remember he now has full pack voltage. 

Pete


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## EVfun (Mar 14, 2010)

gottdi said:


> My DC DC output is isolated. So I can use it to power the controller. I don't disagree but pointed it out. I also posted first because I was trying to trouble shoot the problem. Too bad he did not check to see if he had a low 12 volt battery that dropped below the minimum 8 volt threshold. Yes, he is good now but he needs to fuse that line with a small fuse. No need for more than like an amp fuse in that line. Remember he now has full pack voltage.
> 
> Pete


Does your DC to DC provide 2 separate isolated outputs? If it only provides one (like the Todd PC20-LV I used for years in the Buggy) you really shouldn't connect the +12v to the ksi on the controller. That connection on the Curtis is not isolated from the traction pack so it defeats traction pack isolation from the vehicle. If you have 2 isolated outputs the second one needs the +12v to ksi and -12v to traction pack negative (to complete the circuit.)

You have a very good point, the ksi line should be fused with a less than one amp fuse (even a 1/4 amp fuse is more than enough.) A good 1/4 by 1-1/4 fuse will handle this at any pack voltage a Curtis can handle.


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## Guest (May 6, 2011)

Nope. Just one. But the kelly dc dc is isolated as well as the kelly and synkromotive controller. Never found any chassis power leaking from the main pack. My DC DC works well with my Synkromotive too. Fused with 1/4 amp fuse even at 13.8 volts. My current DC DC is working fine with the Synkro too. Isolated and working just fine. I run my DC DC to a fuse block and run one leg to my controller. I have checked to see if I am getting pack voltage from the chassis and it just is not there. It is isolated. Sorry that the Curtis is not. But that is, I am sure, because the Curtis has mostly been used in low voltage systems and its not an issue. But with high voltages it can be an issue. Maybe someday they will isolate completely so you can use an isolated DC DC to power the controller and not have to worry about full pack voltage into the circuit board for mostly low voltage purposes. I am glad it will handle full pack voltage. I'd for sure go with what Curtis recommends. I will not argue that one bit. 

Pete


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## lou-ace (Jul 21, 2009)

further good news, I finally got around to cleaning my throttle pot and yep, I guess it was pretty dirty, because I sure have a smooth throttle now. No surges or surprises.My throttle was the curtis modle, inclosed in the box. I took it apart, squirted it with cleaner/lubricant and forced air through it 'till dry. It didn't look dirty but it sure drives better. so make sure to clean the pot every once in a while. mine was 4 years old. good luck.


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## davidmillin (Dec 14, 2013)

> On that note why do I need another relay for the pack voltage? why cant I tap a lead from the down side of the microswitch/relayed albright contactor that runns the drive power curcuit? initially I'll try that for a test. wish me luck.


Hi everyone I have been trying to understand why a relay is necessary on the KSI line on a curtis 1221/1231 controller. I understand that it should be pack voltage going to the KSI pin and it needs to be switched and you don't want pack voltage entering the cabin. But the main contactor is switched with 12V why can't you just take a branch from between the main contactor and B+? the only reason I can think of is if your main contactor welded shut you could still switch off the controller with the KSI relay is there any other reason why all the diagrams seem to be using a KSI relay?. Is there any other advantage to using diagram 1 rather than diagram 2?


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## davidmillin (Dec 14, 2013)

I think I've worked out why it is because the KSI pin would always be on because of the current coming through the precharge resistor. Is this a really bad thing though if there is another way of isolating the pack when not driving so the controller doesn't drain your 12V battery?


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## arklan (Dec 10, 2012)

i want to know about this too
but if the key is off and the main contactor is turned off then i dont see any point in having the ksi pin switched like that unless you have a system where your precharge resister is on 24/7


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## EVfun (Mar 14, 2010)

The Curtis controller will use a lot more power if the KSI is left powered. This will increase the voltage drop across the precharge resistor and so the stress on the ripple caps and main contactor when it closes. If you push on the throttle with the Controller precharged and ksi is powered then the car will move a little using the power stored in the caps.


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## arklan (Dec 10, 2012)

EVfun said:


> The Curtis controller will use a lot more power if the KSI is left powered. This will increase the voltage drop across the precharge resistor and so the stress on the ripple caps and main contactor when it closes. If you push on the throttle with the Controller precharged and ksi is powered then the car will move a little using the power stored in the caps.


it cant draw much out of that little ksi wire so it must mean that when your foot is not on the go pedal its still drawing a fair bit of power
which must mean that the curtis "idle" draw is pretty terrible :/


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## EVfun (Mar 14, 2010)

arklan said:


> it cant draw much out of that little ksi wire so it must mean that when your foot is not on the go pedal its still drawing a fair bit of power
> which must mean that the curtis "idle" draw is pretty terrible :/


The logic of the Curtis is powered by the ksi wire. The only draw on the main cables when that is not included is the bleed down resistor for the input caps. I used light bulbs to precharge my 1221b. The voltage drop across a 25 watt bulb with ksi powered was greater than the voltage drop across a tiny 7.5 watt bulb with ksi not powered. With ksi powered my car would move about 2 inches each time the throttle was pressed, using the power stored in the input caps.

A 750 ohm resistor is recommended by Curtis for a 1231 controller. Just 20 milliamps of load from powering ksi will cause a 15 volt drop across that resistor.


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## arklan (Dec 10, 2012)

so if im getting this right, u want the contactor to close first, then the ksi wire to power on?
if there was a switch to connect the ksi wire in the dash *for example *then you could do the normal start up with closing the contactor etc, then flick the switch to activate the ksi wire and drive along no problem, just remember to turn the ksi switch in the dash off after you finished
(no im not gonna do this, i just want to see if im understanding the theory correctly)


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## davidmillin (Dec 14, 2013)

> so if im getting this right, u want the contactor to close first, then the ksi wire to power on?
> if there was a switch to connect the ksi wire in the dash *for example *then you could do the normal start up with closing the contactor etc, then flick the switch to activate the ksi wire and drive along no problem, just remember to turn the ksi switch in the dash off after you finished
> (no im not gonna do this, i just want to see if im understanding the theory correctly)


No the contactor closing and KSI switching on can happen at the same time but you want precharge to happen first. In theory your KSI wire could be switched from a dashboard switch but this is inadvisable as you are introducing traction pack voltage into the cabin also it is easier to have the KSI switching automatically rather than manually switching it on and off


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## arklan (Dec 10, 2012)

so could I just leave the main contactor on 24/7 and use the ksi wire to turn the car on and off?
other than the car moving that tiny bit I mean
would it draw a lot of power like that way?


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## EVfun (Mar 14, 2010)

The main contactor is indispensable. When a Curtis 1221 or 1231 fail it is often in a more-than-full-on state. You need to turn off the main contactor. The ksi wire will turn the car off only so long as the controller is working. Also, the main contactor will draw coil power when it's on. 

Why not have the KSI relay coil operated directly by the ignition switch and take pack power from before the main contactor to the KSI terminal? (include a properly rated fuse) The main contactor can take coil power from the ignition switch through the pot box micro switch to its coil. The precharge resistor can be a high value and left in place across the contactor. The factory recommended, permanently connected, 750 ohm precharge resistor should be at least a 25 watt unit, mounted carefully, as it would dissipate about that much if the controller fails on. 

If you build a precharge circuit the precharge resistor could, with this setup, go from the KSI terminal side of the KSI relay to the controller side of the main contactor. The ignition switch could turn on the KSI relay, but ignition switch power to the microswitch for the contactor should be delayed until the controller precharged to a safe value (unless you always remember to wait X seconds after turning the car on before touching the throttle pedal.)


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## arklan (Dec 10, 2012)

EVfun said:


> The main contactor is indispensable. When a Curtis 1221 or 1231 fail it is often in a more-than-full-on state. You need to turn off the main contactor. The ksi wire will turn the car off only so long as the controller is working. Also, the main contactor will draw coil power when it's on.
> 
> Why not have the KSI relay coil operated directly by the ignition switch and take pack power from before the main contactor to the KSI terminal? (include a properly rated fuse) The main contactor can take coil power from the ignition switch through the pot box micro switch to its coil. The precharge resistor can be a high value and left in place across the contactor. The factory recommended, permanently connected, 750 ohm precharge resistor should be at least a 25 watt unit, mounted carefully, as it would dissipate about that much if the controller fails on.
> 
> If you build a precharge circuit the precharge resistor could, with this setup, go from the KSI terminal side of the KSI relay to the controller side of the main contactor. The ignition switch could turn on the KSI relay, but ignition switch power to the microswitch for the contactor should be delayed until the controller precharged to a safe value (unless you always remember to wait X seconds after turning the car on before touching the throttle pedal.)


could u draw this in to a wiring diagram?
this seems like a good idea, it would be similar to a tesla


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## EVfun (Mar 14, 2010)

arklan said:


> could u draw this in to a wiring diagram?


Here is a quick sketch of my wiring idea where the precharge resistor is always connected and KSI is not powered until the key switch it turned on. 

This is a simple way of handing this, similar setups where quite common when the Curtis controller was more in use by EVers. Some users didn't want the constantly switching contactor noise, so other more safe and less safe setups where also used. One of my favorites used a reed switch on a power cable so that if the potbox switch sensed the throttle was released and yet power was flowing through the pack cable that would latch a relay which would cut power to the main contactor. 

If you want the controller to not precharge until the key switch is turned on then the precharge resistor (shown as 750 ohm) needs to be moved so one is attached to B+ and the other end to KSI. You also need to add an appropriate delay circuit after the 5A 15V fuse or always remember to wait for the controller to precharge before touching the throttle. If you go this route you likely want to use a lower value resistor for the precharge to speed up the process. However, the power rating of the resistor becomes an issue if the controller fails. The best delay circuit would wait X seconds, check the voltage at B+, and let power through if the controller was within a few volts of pack + or turn off the KSI relay and lock out if the controller failed to precharge.


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## honn1002 (Nov 26, 2008)

I don't like the contactor to turn off and on via the pot box micro switch during driving. I drew my own wiring diagram and wired up my electric Civic as shown in the attached diagram. I used a much lower resistor for precharge but the resistor has to be sized up the heat dissipation. The precharge is controlled by a solid state relay. The solid state relay also turns on my dc-dc converter.


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