# Contactor wiring



## rctous (Jun 18, 2008)

stormcrow said:


> So it turns out I am a moron and believe I have purchased the wrong contactor. The system in my car runs off of 72 volts. When I was ordering the contactor, I looked for one that said 72v on it and bought it. I have already recieved the contator and noticed that the 72v number that I saw was the coil size. So I have two questions.
> 
> 1) Am I correct in assuming that the coil size is the amount of juice it takes to activate this contactor?
> 2) If that is the case, is there any possible way to get a 72v coil to close with 12v, possibly by wiring in something before the contactor?
> ...


you can make it work by using the traction pack voltage to run through a 12 relay and trigger it that way,,,,,,,,,,,,,,,,,,,,,,,,but givin the choice and if you have time return it and get one with a 12 vdc coil I would do that instead,,, every extra part you add is more that can break


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## stormcrow (May 28, 2008)

Finally got a hold of the company I ordered it from. Just wanted to let anyone who is interested know that it turns out that I can actually use the contactor I already have. The person I talked to said that I can run a 72v wire off of the battery pack and through the ignition switch. It should be fine because there will be very low amperage going through it (less than 5 amps). He sent me a wiring diagram and said to throw a 5amp fuse on there. He also said that it is actually a little bit safer to do it this way because then my 12v system and the high voltage system will be completly seperate.


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## TX_Dj (Jul 25, 2008)

stormcrow said:


> Finally got a hold of the company I ordered it from. Just wanted to let anyone who is interested know that it turns out that I can actually use the contactor I already have. The person I talked to said that I can run a 72v wire off of the battery pack and through the ignition switch. It should be fine because there will be very low amperage going through it (less than 5 amps). He sent me a wiring diagram and said to throw a 5amp fuse on there. He also said that it is actually a little bit safer to do it this way because then my 12v system and the high voltage system will be completly seperate.


Could you send the wiring diagram? I disagree with the statement that running the 72v up into the steering column and attached to the ignition switch would separate the 12v and 72v system (in fact it would tie the two together, no bueno!)

Either that, or I'm misunderstanding what you're saying.

Additionally, 5 amps at 72v is 360w... imagine how hot three 100w and one 60w light bulbs would be.... And the potential for that kind of heat showing up in your steering column.


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## stormcrow (May 28, 2008)

This is what I was sent:
http://www.alltraxinc.com/files/Doc100-045-A_DWG-AXE-No-Reverse-wire-dia.pdf
I was also told that wiring it through the key switch is what they recommend in their "small car kit". I asked him again to be sure I understood him right that I could run 72 volts through the existing key and he said yes. He did say I would need a 18-14 gauge wire going through there but I dont think it is running at the full 5 amps. More like 1 or 2.
Admittedly, I'm not exactly sure at how an ignition switch works in a normal car, so I dont know if wiring it this way would tie the two systems together or not. I think I'll email this guy back and ask him to be triple-sure.


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## frodus (Apr 12, 2008)

I would advise that you NOT put your pack voltage anywhere NEAR the stearing column.


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## TX_Dj (Jul 25, 2008)

What is shown in that diagram is a KSI relay. What is not shown is the 12v input to the KSI relay. The 12v signal from the key switch triggers the key switch interlock (KSI) which in turn triggers the main contactor.


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## frodus (Apr 12, 2008)

that would indeed be the safest solution.


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## stormcrow (May 28, 2008)

That makes way more sense than anything else I have been told. I am going to wait until I get my throttle before I make my final decision on if I'm going to send the contactor I have back or not. I am thinking I may end up keeping it and just add a relay as suggested. I'm just wondering why nothing like this was ever mentioned in their information on their small vehicle kit. There are no relays or anything in their kit.
Does anyone out there have a suggestion on where I could pick up a relay?
I am also looking for a relay or solenoid for my charging system. I would like one that, when powered by 12v, disables the other side. That way the charger would be automatically disconnected when the car is under power. The only thing is though I do not know if such an object exists.
Thanks for all the feedback.


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## frodus (Apr 12, 2008)

just make sure the smaller relay is rated for that voltage DC, because if you get a 12V relay (rated for 12V on the output), and use it at 72V, and the contacts arc and weld shut, you will not be able to disconnect the contactor, and need an alternative way to disconnect the power to the contactor.


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## fugdabug (Jul 14, 2008)

stormcrow said:


> Finally got a hold of the company I ordered it from. Just wanted to let anyone who is interested know that it turns out that I can actually use the contactor I already have. The person I talked to said that I can run a 72v wire off of the battery pack and through the ignition switch. It should be fine because there will be very low amperage going through it (less than 5 amps). He sent me a wiring diagram and said to throw a 5amp fuse on there. He also said that it is actually a little bit safer to do it this way because then my 12v system and the high voltage system will be completly seperate.


Did you buy an Albright Contactor? IF so, the 72VDC is the traction system voltage and the coil will use standard 12VDC from the ignition or directly from the system (low voltage system 12V that runs the lights etc...) with a switch. Buy a good book like Bob Brandt's "Build your own electric vehicle'' on page 250 is the example of the basic wiring system that I used... minus a dc/dc and 'interlock' (I use a plain old Anderson connector to disconnect when charging)... There are a million voices with a million opinions and pieces of advice out there... get this book READ IT! and then go to it. YES it isn't perfect, but the basic wiring is what you need to make your system go! You can always tweek it from there!
P.S. You aren't stupid or asking dumb questions.
P.P.S. Remember the cover of the "Hitchhikers Guide to the Galaxy"...DON'T PANIC!
I did it and my 72VDC ran fine... until I tried to upgrade to 144VDC with a crappy controller! BUT the wiring schematic works!
calm down... you can do it.


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## stormcrow (May 28, 2008)

fugdabug said:


> Did you buy an Albright Contactor? IF so, the 72VDC is the traction system voltage and the coil will use standard 12VDC from the ignition or directly from the system (low voltage system 12V that runs the lights etc...) with a switch. Buy a good book like Bob Brandt's "Build your own electric vehicle'' on page 250 is the example of the basic wiring system that I used... minus a dc/dc and 'interlock' (I use a plain old Anderson connector to disconnect when charging)... There are a million voices with a million opinions and pieces of advice out there... get this book READ IT! and then go to it. YES it isn't perfect, but the basic wiring is what you need to make your system go! You can always tweek it from there!
> P.S. You aren't stupid or asking dumb questions.
> P.P.S. Remember the cover of the "Hitchhikers Guide to the Galaxy"...DON'T PANIC!
> I did it and my 72VDC ran fine... until I tried to upgrade to 144VDC with a crappy controller! BUT the wiring schematic works!
> calm down... you can do it.


First of all, I really appreciate the encouragement.
Yes it is an Albright contactor. It is this one: 
Contactor Albright SW180-235, 72 Volt Coil
So I believe that since the coil is 72V, that means it takes 72V to activate it, not twelve. To be sure I hooked it up to an old 12V battery charger and it didnt do anything. (unless I had it hooked up wrong. The contactor didnt come with any instructions.) 
I did pick up Bob Brandt's book. It was one of the first things I did once I started getting interested in doing something like this. I learned a lot but have found it doesnt explore all the little details (hence my confusion with this contactor). I will take another look at page 250 when I get home tonight. And I believe the second edition of that book is coming out later this month. Maybe there will be more info in the new edition.
I am thinking I will most likely keep the contactor that I have and just wire in a 12V relay. I looked up the relay that KiwiEV used in his car and found one online for $25. It will take slightly more wiring to make it work, but I think the end result will be slightly more safer, expecially since I am planning on putting a fuse on the line going to the relay.
And speaking of relays, I am still wondering if such a relay exists that would let me disconnect the battery charger when the car is under power. It would be the most ideal solution, I just dont know if there is such a relay.


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