# Question About Keyswitch Inputs & Wiring



## jonodatinvento (Jan 16, 2019)

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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## BAstereo (Dec 28, 2018)

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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## cricketo (Oct 4, 2018)

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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## jonodatinvento (Jan 16, 2019)

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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## frodus (Apr 12, 2008)

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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## potvinguy (Jul 24, 2016)

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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## potvinguy (Jul 24, 2016)

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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## jonodatinvento (Jan 16, 2019)

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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## potvinguy (Jul 24, 2016)

jonodatinvento said:


> 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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## jonodatinvento (Jan 16, 2019)

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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## poprock (Apr 29, 2010)

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


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## cricketo (Oct 4, 2018)

frodus said:


> The controller shown here doesn't control the contactor.


Good catch!


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## jonodatinvento (Jan 16, 2019)

cricketo said:


> Good catch!



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.


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## potvinguy (Jul 24, 2016)

poprock said:


> 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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## potvinguy (Jul 24, 2016)

jonodatinvento said:


> 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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## frodus (Apr 12, 2008)

jonodatinvento said:


> 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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## jonodatinvento (Jan 16, 2019)

potvinguy said:


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



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!


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## jonodatinvento (Jan 16, 2019)

frodus said:


> 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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## potvinguy (Jul 24, 2016)

jonodatinvento said:


> 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!


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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## poprock (Apr 29, 2010)

There is a 6 page discussion of this in the wiki " pre-charge, what it is and do I need to do it "


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## potvinguy (Jul 24, 2016)

poprock said:


> There is a 6 page discussion of this in the wiki " pre-charge, what it is and do I need to do it "


Great link! Here is part of the article applicable to EVs:

Pre-charging is commonly used in battery electric vehicle applications. The current to the motor is regulated by a controller that employs large capacitors in its input circuit. Such systems typically have contactors (a high-current relay) to disable the system during inactive periods and to act as an emergency disconnect should the motor current regulator fail in an active state. Without pre-charge the high voltage across the contactors and inrush current can cause a brief arc which will cause pitting of the contacts. Pre-charging the controller input capacitors (typically to 90 to 95 percent of applied battery voltage) eliminates the pitting problem. The current to maintain the charge is so low that some systems apply the pre-charge at all times other than when charging batteries, while more complex systems apply pre-charge as part of the starting sequence and will defer main contactor closure until the pre-charge voltage level is detected as sufficiently high.


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## poprock (Apr 29, 2010)

Just a point about higher voltages. The Curtis diagrams are for low voltage ; in AU the National Code of Practice has these requirements. "HAZV: Hazardous Voltage. Any voltage that may be greater than 60V DC or 25V AC at any time. (Typically the voltage of the main traction battery pack or the motor drive circuits). 2.10 Hazardous Voltage Disconnect The power on procedure must be applied via a key switch. It must not be possible to remove this key in any position that energises the drive train or makes active driving possible. Disconnection of the traction pack from the rest of the traction circuit must be by a contactor operated by the ignition switch. An inertia switch should be employed to disconnect the traction pack from the rest of the traction circuit in the event of a collision. Additional switches may be installed to interrupt the supply to assist the user or repairer of the vehicle. For example, a toggle switch may be installed to enable the driver to shut down the battery supply without resorting to turning off the ignition key, as switching off the ignition will also disable devices such as brake boosters and also potentially lock the steering. The circuit depicted in Figure 2 below depicts one example of how the circuit could be designed."
"Your local regulations may differ."

Figure 2 Typical Circuit Showing Ignition Switch, Battery Pack Contactors and Optional HV Disable SwitchThe circuit depicted in Figure 2 below depicts one example of how the circuit could be designed.
The circuit depicted in Figure 2 below depicts one example of how the circuit could be designed. "
Sorry, unable to upload diagram. Look up NCOP 2:9,10 {AU version}


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## jonodatinvento (Jan 16, 2019)

potvinguy said:


> 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.



Ah I didn't think the terminal could take that much current but it is referenced internally to the B- bus.


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## jonodatinvento (Jan 16, 2019)

poprock said:


> The power on procedure must be applied via a key switch. Disconnection of the traction pack from the rest of the traction circuit must be by a contactor operated by the ignition switch. An inertia switch should be employed to disconnect the traction pack from the rest of the traction circuit in the event of a collision. Additional switches may be installed to interrupt the supply to assist the user or repairer of the vehicle.



Ah this lays it out all in one place. I'm not sure what U.S. regulations are on the subject... Time to do some more reading.


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