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Discussion Starter #1
Alright, so I read another thread on here about how the keyswitch and relay are supposed to be wired, but I still don't fully understand it. I've attached the diagram for a Curtis 1231C controller for reference.



So in my head, the keyswitch (the stock ignition switch in the dash) accepts the 12V from the accessories battery and allows it to travel to a relay, and that relay closes when the current is applied to it allowing pack voltage from the traction batteries to reach the controller. Then the controller is allowed to turn on the contactor for driving.


Now where it confuses me is the inclusion of the potbox and the contactor. The other thread stated the power to the KSI relay has to go through the potbox to satisfy those conditions. What does that mean?


And there are wires shown leading to the contactor, and the relay is shown to have some connections there too. That seems to allow the contactor to close...?



P.S. Sorry for the mass of text, I'm trying to wrap my head around this lol. Any help is appreciated.
 

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I am now here, so this might be incorrect. But it looks like the wire in question comes from the N.C. terminal. I suspect that would just pass the power throught, not throttle input.
 

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That potbox has an additional switch. When the pedal is depressed, switch is probably in the open position, so main contactor is also open regardless of all other conditions. Once you start pressing the accelerator pedal, first thing that happens is the main contactor will engage - you will hear a distinct click. Only as you press further the vehicle will actually start to accelerate.

On some golf carts they don't have that relay and instead have a "tow" switch. I think one of the thing it does is energizing the pre-charge resistor, but I could be wrong.
 

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Discussion Starter #4
Ah I see. Yes, it seems like the 12V just passes through the pot and travels back to the battery. That explains why it controls the contactor too.
 

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The controller shown here doesn't control the contactor.

The circuit for the Contactor coil is from the 12V Aux battery positive, through a small fuse, through the keyswitch, through a small switch on the throttle and into the coil, and back to the 12V negative. It also controls the KSI relay that connects pack voltage to the KSI input on the controller.

When key switch is on, and the throttle is not pressed, the contactor won't close.
When key switch is off, and throttle is pressed, the contactor won't close.
When you turn key switch on, and press the throttle, the throttle switch closes and the contactor closes.

The throttle has 2 parts. A small microswitch, and also a potentiometer. The potentiometer is what goes to the controller and controls the power to the motor.
 

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I use the Curtis in my '78 Bug. Here's the easy way to wire it:
The potbox switch and extra relay are not needed.

Also that wiring Curtis-to-motor looks fishy. Let me dig out my documentation and get back to you.
 

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OK, I got it. The wire from Curtis A2 to motor A2 should not be used in EVs. It provides "plug braking," an electrical braking used in low speed, low load applications like golf carts. See my install:


Note that only 3 terminals of the Curtis are used and only 2 wires go to the motor.
 

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Discussion Starter #8
So what was the original purpose of the throttle keyswitch on the potbox? To prevent unauthorized driving?

And I have heard that A2 shouldn't be used. Does this also apply to series wound DC motors?
 

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So what was the original purpose of the throttle keyswitch on the potbox? To prevent unauthorized driving?

And I have heard that A2 shouldn't be used. Does this also apply to series wound DC motors?
The potbox switch might have been part of a safety thing, so the traction power wouldn't be engaged unless the throttle had been moved.

This model Curtis is designed for only series DC motors.
 

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Discussion Starter #10
Ok, makes sense.

So basically the keyswitch is only activating the contactor which powers the controller, and you shouldn't use the A2 bus on the motor or the controller.

Additionally, the potbox switch is not required and the controller doesn't need a KSI input to turn on or provide power.
 

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So without a high voltage isolation switch, does this make potvinguy's system always active through the pre-charge resistor ?
 

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So without a high voltage isolation switch, does this make potvinguy's system always active through the pre-charge resistor ?
Yes, it does. The pre-charge resistor keeps the big capacitors in the Curtis controller fully charged so that when the contactor closes we don't have a big inrush current, which is bad for both the contactor and the capacitors. The resting current through the pre-charge resistor is tiny and has no significant effect on the traction battery.
 

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Ok, makes sense.

So basically the keyswitch is only activating the contactor which powers the controller, and you shouldn't use the A2 bus on the motor or the controller.

Additionally, the potbox switch is not required and the controller doesn't need a KSI input to turn on or provide power.
Oops! I forgot the KS1 input, which is required to turn on the Curtis. Here's how I did it:


When the contactor closes, it not only supplies traction power to the Curtis, but also turns it on. I gotta keep better documentation....
 

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Yeah, I realized that lol. If a controller does control the contactor, how would this setup change? I know the OpenReVolt controller has a 12V out for the contactor.
On some controllers like Curtis 1236/38 and Sevcon Gen4 AC controllers, you only put pack voltage to KSI when you want to start. There's an internal precharge for the on-board capacitors through the KSI connection. Once they charge fully, the controller outputs a voltage to the contactors to close the main contactor.

With older Curtis and Alltrax DC controllers, there's no contactor output or have an internal precharge. Precharge and contactor control must be done externally.
 

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Discussion Starter #17
Oops! I forgot the KS1 input, which is required to turn on the Curtis. Here's how I did it:


When the contactor closes, it not only supplies traction power to the Curtis, but also turns it on. I gotta keep better documentation....

So the 12V current from the keyswitch doesn't return to the 12V battery? It goes to the KSI input and the B+ terminal?



Haha, I don't have any documentation cause I haven't done anything like this yet! :D
 

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Discussion Starter #18
On some controllers like Curtis 1236/38 and Sevcon Gen4 AC controllers, you only put pack voltage to KSI when you want to start. There's an internal precharge for the on-board capacitors through the KSI connection. Once they charge fully, the controller outputs a voltage to the contactors to close the main contactor.

With older Curtis and Alltrax DC controllers, there's no contactor output or have an internal precharge. Precharge and contactor control must be done externally.

That's super convenient lol. So with those you'd wire the keyswitch to a relay which closes for current to travel to the KSI input, and the relay returns the 12V in to the 12V battery?



And it seems like the 1231C has the same requirements as older models in terms of wiring. Ex. Precharge Resistor on Contactor and confusing wiring for contactor control.
 

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So the 12V current from the keyswitch doesn't return to the 12V battery? It goes to the KSI input and the B+ terminal?



Haha, I don't have any documentation cause I haven't done anything like this yet! :D
No. I should've been more clear with my diagram. Here is the whole deal:



The contactor is controlled by the keyswitch with 12v. The output of the contactor, which is the traction battery, both supplies high current to the Curtis at the B+ terminal and turns it on at the KS1 teminal. And remember the cable from A2 to A2 is not used in road vehicles as it is for plug braking on golf carts and forklifts and such.
 
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