# Wiring Schematic--Tapping pack for Reversing Contactor



## elanmel (May 3, 2010)

After finally getting the batteries and motor mounted, I will be starting to wire together my spitfire this weekend. I am using such a collection of used/found parts, that I can hardly wait to find the first thing that will blow/break/pop!

One current question is how to wire a 48v reversing contactor I pulled from my donor forklift. If anyone can point me towards a schematic that shows one of these it would help. I know I'll be tapping into the pack at 48v, but I am not sure which wire goes to which side of this thingy...


----------



## elanmel (May 3, 2010)

If I wanted to run straight from my 120v pack to this 48v reversing contactor (short bursts just to back up), how can I safely/easily/cheaply reduce voltage through this unit? 

A friend suggested wiring 3 x 24v Headlight lamps in series in the reverse circuit. How can I do this--do I run my 2/0 wire through three lamp bases? How would I connect them in line? 

Hey, if I mount the lights on my rear bumper I could have the worlds brightest backup lights...


----------



## major (Apr 4, 2008)

elanmel said:


> If I wanted to run straight from my 120v pack to this 48v reversing contactor (short bursts just to back up), how can I safely/easily/cheaply reduce voltage through this unit?
> 
> A friend suggested wiring 3 x 24v Headlight lamps in series in the reverse circuit. How can I do this--do I run my 2/0 wire through three lamp bases? How would I connect them in line?


Hi elan,

Do you know how a contactor works? How 2 contactors are used for motor reversing? That a contactor has main contacts and a separate coil? That the voltage rating for the contacts is independent of the coil voltage?

What controller do you have? What motor?

Have you searched the wiki on this site? Done other research on how to wire a contactor or reverse a motor? Looked for the contactor specification per the part number and manufacturer of the contactor you have?

Once you gain some basic knowledge and relate some basic system information, I think one of us can help you. Until then, what you put up in these two posts is confusing to me and I am afraid anything I say to try to help will only confuse things further 

Perhaps start with a description and diagram of your EV project 

Regards,

major


----------



## major (Apr 4, 2008)

Here's a wiring diagram from the Curtis website.


----------



## peggus (Feb 18, 2008)

Hi Elan, I see I may have added more confusion than help. 

Can you post some more pictures on your contactor I'll help you figure out how to hook it up. I need to see all the connections and the part number.

Thanks


----------



## elanmel (May 3, 2010)

Peter, thanks for the offer of help. 

I thought I recalled a discussion on this forum on using one of these 36/48v reversing contactors with a 120v pack, by putting a load on the line as you suggested, but didn't explain my original questions clearly. Sorry all!

I am building a Spitfire, basically following the models that Peggus and Bottomfeeder built. I am using Bottomfeeder's schematic for my project, but need to wire in a reversing contactor. I can find wiring schematics for 120v contactors (eg., the Albright 202), but can't find schematics for others who may have used these lower rated contactors (either by tapping the pack or by reducing voltage across the reverse circuit from 120v to 48v). 

I am using an 11" forklift motor, a logisystems controller, as well as a lot of other used parts, including the reversing contactor pictured above. It is the same as this one:

http://cgi.ebay.com/GE-EV-100-150-A...aultDomain_0&hash=item1c1263a1d4#ht_500wt_922.

I tried to search for a manual for this part, but nothing came up.


----------



## major (Apr 4, 2008)

elanmel said:


> I can find wiring schematics for 120v contactors (eg., the Albright 202), but can't find schematics for others who may have used these lower rated contactors (either by tapping the pack or by reducing voltage across the reverse circuit from 120v to 48v).


Hey elan,

I don't understand what you mean by reverse circuit  Just wire as shown in the Curtis diagram in post #4. You should never open and close the contactors under load (while current is flowing), so the higher than rated battery voltage will not cause a problem. Besides you are on the load side of the controller, so the controller will reduce the voltage anyway when in reverse and you'll have them in the forward circuit to boot.

It is the coil voltage which is likely 36/48 volt rated. Get a power supply or a couple of batteries and see what the pull in and hold voltage is needed for the coil. You are doing a car, so will have 12 volts, right? If it isn't enough and you need 36 or 48 volts, see if you can get an inexpensive DC/DC converter. Measure the coil resistance and figure the watts. Likely to be less than 50 watts. An eBay converter might cost you $10. Or once you know the coil resistance, figure a simple dropping resistor value and put it in series with the coil. That's easy to do and you don't need light bulbs 

Regards,

major


----------



## peggus (Feb 18, 2008)

Ok, I labeled the terminals on the contactor per the Curtis diagram.

You'll need a dropping resistor in line with your selector switch as Major suggested. and you'll need a beefy selector switch than can switch 120V DC. I happen to have one here that you can use, I'll leave it with Dan on Friday if you're not there.

Can you measure the coil resistance (the small terminals) with a multimeter?, I may have a suitable dropping resistor as well.


----------



## elanmel (May 3, 2010)

Major/Peggus--thanks for the guidance, and for your patience as I get the question straight. 

I have a DPDT switch from KTA rated for this job, so I think I am okay on that. The coil resistance measures at 33 ohms. Am I looking at three dropping resistors here (1 on the forward side, 1 on the reversing side of the contactor, and one between the contactor and the switch??). If you have any of these parts available, I would be happy to take them off your hands. FWIW, I also need a few more 2/0 lugs and a pre-charge resistor!

I will actually be at the Brewery tomorrow (right next to Dan's studio). If there is a convenient time I can definitely pop over there--let me know. 

I owe you guys a big thanks (again!).


----------



## major (Apr 4, 2008)

elanmel said:


> The coil resistance measures at 33 ohms. Am I looking at three dropping resistors here (1 on the forward side, 1 on the reversing side of the contactor, and one between the contactor and the switch??).


No. You just need a single resistor. Since the coil resistance is 33 Ω and it apparently can work on 36V, you need 1.09 amps of coil current. If you use 120V as a source, you need a total resistance of 110 Ω. Subtract the 33 Ω and your resistor needs to be 77 Ω. It has to dissipate I²R, or 91 watts. 

This resistor goes in the control circuit. Back to the diagram in post #4, the power circuit is represented by heavy lines (your 2/0 cable) and the control circuit is the thin lines, like #18 wire. The power circuit connects to the contactors at S1, S2, A2, M- as Peter outlined in post #8 with 2/0.

The control circuit connects to the small terminals on the contactor coils represented on the diagram at the far right. It shows forward and reverse coils with a diode across each and each connected to the F R switch. On the Curtis, this coil/switch control circuit is connected to the remainder of the control circuit. I imagine the rest of the control circuit in your case will be 12V. So this coil/switch circuit needs to be wired to your 120V battery with a fused branch. The 77 Ω resistor goes in between the fuse and the center pole on your switch.

Also, if you want to avoid running high voltage to the dashboard for the F R switch, you can use a 12V control relay. You will also need the diodes across the contactor coils as shown on the diagram or you'll burn the switch contacts in short order.

It sounds like Peter is in your neighborhood. Hopefully he can help you.

Regards,

major


----------



## peggus (Feb 18, 2008)

So I'll look around for a 80Ohm 100W+ resistor for you. I'm not sure I have one but I do have Diodes. I'm going to be at Dans house tonight. I'll leave the parts with him and you can pick them up whenever it's convenient.

I see Major already gave excellent answers to your questions.


----------

