# Key switch/contactor setup



## TheSGC (Nov 15, 2007)

I am designing my wiring, and I am wondering how people out there are connecting your contactors to your ignition switch. 

Are you using a 12 volt relay and sending the pack voltage through it to activate the contactor? I am using SW80B contactors, with two in parallel for 200 AMP continous and planning a 96 volt system.


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## 3dplane (Feb 27, 2008)

SGC!
Hi! I'm no expert on this but a quick look at that contactor showed that it's coil is 12V,so I'm sure pack voltage would smoke it quickly.Does it's label state what the current draw is when on? The reason I'm asking is maybe if the current draw is small the ignition switch could handle it without a relay.
Anyhow hope someone with actual knowledge on this chimes in as now I'm 
curious as well. I just didn't want you to try pack voltage to activate it.
Barna


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## Coley (Jul 26, 2007)

Mine has the ignition switch turning on the power to the main "ON" switch, that feeds the 12volt coil on a 48 volt continuous duty solenoid. 
The 48 volt solenoid then sends the 72 volt pack juice to the main 72 volt contactor. The contactor sends 72 volts to the Alltrax controller.

On the neg side of the pack, a pair of 48 volt cont duty solenoids, in parallel, turn on the NEG side to the controller.

This isolates the pack at both ends, preventing the resister across the main contactor from feeding to the controller, when the car is shut off.

I used Alltrax's wiring diagram, for most of my 72 volt system.


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## 3dplane (Feb 27, 2008)

Coley!
What is your 'ON' switch? (relay,solenoid,switch) My alltrax didn't come with diagrams except for fuse installation. Thanks. Barna.


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## helixev (Nov 7, 2007)

In my truck the start cable was about 14awg... I think (from memory). You should check the manual for your car and see what the ignition fuse is rated at and what gage the cable is to see if you could directly drive the contactor.


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## TheSGC (Nov 15, 2007)

My contactor is labeled as Type: SW80B-783T Volts: 60 CO. Curtis says it can be used up to a 96 volt system because of the magnetic blowouts, but they dont mention if its the coil or just the contacts. Maybe I should just plug it into the 12 volt aux battery and see what happens.


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## MARTY (Dec 16, 2007)

Hi All;
I have a I think kilovac contactor, I have it hooked up to the old coil (Ignition) wire... I do not at present have the By-pass resistors hooked accross it, As It has voltage going to it on both ends, and if I put the resistance accross it, I will short out the batteries accross the resistor, OR do I have something hooked up WRONG ????
I have followed the Diagram in the Curtis Controller Manual... Except for the resistor accross the contactor... It seems to work ok for me, but I don't want to burn out the contactor or shorten its life...
THANK YOU Marty


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## Coley (Jul 26, 2007)

3dplane said:


> Coley!
> What is your 'ON' switch? (relay,solenoid,switch) My alltrax didn't come with diagrams except for fuse installation. Thanks. Barna.


Radio Shack has a Red hooded "Missile Launch" type switch.

That is what I use. You raise the hood and turn on the switch. To shut it off just push the hood down.

For diagrams for Alltrax go to: 

http://www.alltraxinc.com/Doc_Depot.html


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## Twilly (Jan 22, 2008)

I used the old +12v feed to the fuel pump to activate the main contactors... I figured then, If I was in an accident, the factory inertia switch would kill power to the main contactor, in turn killing power to the controller/motor


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## major (Apr 4, 2008)

MARTY said:


> Hi All;
> I have a I think kilovac contactor, I have it hooked up to the old coil (Ignition) wire... I do not at present have the By-pass resistors hooked accross it, As It has voltage going to it on both ends, and if I put the resistance accross it, I will short out the batteries accross the resistor, OR do I have something hooked up WRONG ????
> I have followed the Diagram in the Curtis Controller Manual... Except for the resistor accross the contactor... It seems to work ok for me, but I don't want to burn out the contactor or shorten its life...
> THANK YOU Marty


Hi Marty,

Is the resistor you left out the pre-charge resistor? If so, that may shorten the life of your contactor. Each time you close that contactor, connecting the battery to the controller, there will be an arc. This is because the controller contains capacitors, when uncharged, after the controller has been off for a while, and will cause an arc to occur as the contacts close. This is why a pre-charge resistor is used. It limits current from the battery to the controller caps and charges them up to the battery voltage (or near it) so when the contactor closes, there is little or no potential between the contacts and no arc.

Regards,

major


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## MrCrabs (Mar 7, 2008)

major said:


> Hi Marty,
> 
> Is the resistor you left out the pre-charge resistor? If so, that may shorten the life of your contactor. Each time you close that contactor, connecting the battery to the controller, there will be an arc. This is because the controller contains capacitors, when uncharged, after the controller has been off for a while, and will cause an arc to occur as the contacts close. This is why a pre-charge resistor is used. It limits current from the battery to the controller caps and charges them up to the battery voltage (or near it) so when the contactor closes, there is little or no potential between the contacts and no arc.
> 
> ...


You also shorten the life of the controller. The large inrush current is no good for the capacitors inside the controller.


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## MARTY (Dec 16, 2007)

Hi All;
THANK YOU for your replys .... I will when I get the car back from the shop, put the resistors in (pre-charge), I have more than one to get the amperage I need....
But I still have the question --- By putting in the Resistor, doesn't that put a load on the 96 Volt Batteries all of the time ????   Thus shortening my range and battery life ????
THANK YOU Marty


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## elevatorguy (Jul 26, 2007)

MARTY said:


> Hi All;
> THANK YOU for your replys .... I will when I get the car back from the shop, put the resistors in (pre-charge), I have more than one to get the amperage I need....
> But I still have the question --- By putting in the Resistor, doesn't that put a load on the 96 Volt Batteries all of the time ????   Thus shortening my range and battery life ????
> THANK YOU Marty


After the capacitors are charged, there is virtually no current passing through the precharge resistor. This will not affect your range or battery life.
Jerry


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## TheSGC (Nov 15, 2007)

I am still trying to fiugre out this contactor thing and when I tried applying 12 volts to the tabs nothing happens.

I am now trying to get my wiring done and these contactors are quite a pain. There must be something simple that I am missing. I just sent an e-mail to Curtis, but I am not holding my breath. The data sheet on their website was pretty useless when it came to the actual wiring on the contactors.


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## e_canuck (May 8, 2008)

Hi all.
Newb question.
What capacitors? The ones inside the controler?

Thanks.

DP


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## 3dplane (Feb 27, 2008)

e canuck! Yes.the caps in the controller.
The SCG! It would be nice to find out the correct coil voltage for your particular contactor because too little will not provide enough hold-in force but too much will smoke the coil.(too little probably good for system testing only).And don't forget about the diode as well across the coil(of the contactor).Barna


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## elevatorguy (Jul 26, 2007)

If you have a ohm meter, check the resistance on the contactor coil. You should get a reading of 9-15 ohms for a 12 volt coil. If the resistance is a lot higher then it is not a 12 volt coil, if no resistance at all it has a open in the coil.
http://www.bohlinger.biz/sitebuildercontent/sitebuilderfiles/sw80albrights.pdf
Jerry


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## elevatorguy (Jul 26, 2007)

DP,
The capacitors are the ones inside the controller.
Jerry


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## TheSGC (Nov 15, 2007)

Wow, it measured 482 ohms. So its somewhere between 60-96 volts for activating it, and the actual contacts themselves are rated for 96 volts with the magnetic blowouts.

Now I have to make a starting circuit of sorts that will use a 12 volt relay to pass 60 volts to these things when I turn on the car.


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## Tom Thomson (Jun 11, 2008)

Coley
FYI doubling up on small contacts (parallel) to increase ampacity is a no-no in industrial wiring.
tommyt


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## VDubber (Jun 2, 2008)

EV200 4A contactors are now down to $80 (at kta-ev.com). I would suggest that instead - it has a built-in economizer (uses less power to run) and snubber diode and is sealed. Rated at 2000VDC and 200A continuous. The coil runs at 9-36V.


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## TheSGC (Nov 15, 2007)

I am sticking with the SW80B since my budget has run out. I am going to just build a starting circuit that uses MOSFETs to activate the contactors, and it will also have a few status lights and such. I am actually building a water-proof box with the contactors, circuit breaker, starting circuit and other wiring so it will be simple to setup and install.

I know about industrial uses and parallel contactors, but I am using my SW80B in parallel because it is designed to be. I never got the hardware to put them in parallel so I have to make my own setup.


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