contactors?

[Jay64]

I sat down and played with just the kill switch and the test battery for a while. I tried to be a liitle more careful on exactly how everything was wired up. One thing I found is that the switch sometimes doesn't go all the way into the off side unless pushed very deliberately, it's a pretty old switch. I got it to start working pretty consistantly. I think it was a matter of sloppy wiring and not properly putting the switch all the way into position that was causing the earlier mentioned discrepancies. I got it to consistantly show voltage when switched to off and consistantly show no voltage when switched to run, which goes along with what TD was saying. I then wired it into the whole contactor circuit. When the key switch was on, and the kill switch was in the run position I could get 12.9v at the leads that would normally connect to the controller, but I still didn't have any light with the test light. When I turned the kill switch to off, I got between 0.5 and 0.7v at those same lead ends. When I turned the key switch off, I got absolutely nothing with either position of the kill switch.
When I took the diode off the contactor, I started getting 6.8v when the kill switch was in the off position. So apparently I am getting 12v but not a lot of amps through the system when the kill switch is in the run because all of the power is bypassing the contactor, but going through the resistor. But it seems when I activate the contactor by turning the kill switch to off, only about half the volts are getting through. Does that mean that something is wrong with my contactor?

 

[Jay64]

I just checked the diode I was using and it conducts in both directions.

 

[TylerDurden]

Good pix, dude...

The diode appears to be installed the opposite direction it should be. That might be the reason it is shorted. Time for another. (You did check it by itself... not connected to the coil?)

You won't get the test light to illuminate until the contactor closes. Since you are feeding the system 12V, it prolly won't close due to low voltage. You could try 48V, 60V then 72V. It will make a click when it closes, like the solenoid of an ICE's starter motor.

 

[Jay64]

I had read somewhere that the cathode, the side marked with the line, was to be connected on the - side and the anode was to be connected to the positive side. Is that wrong?

I will re-try my circuit afterwork today with my 48v battery pack. That is a good point that kinda crossed my mind earlier when I was testing, but if something wasn't set up right, I didn't want to put even more power to it. But I think this contactor is a 24-72v contactor, so I guess that would mean it won't work on 12v.

Oh, yeah, I had also read that there is a difference between a signal diode and a rectifier diode. And that you need to be a little extra careful when sodering a signal diode. Unfortunately, when I ordered the diode, I just stated that I needed a diode for a contactor and they sent me something, but didn't tell me what kind. Can anyone tell if this diode is a signal or rectifier diode? Could that be a reason that it doesn't work now? There also was that one point when the whole circuit got really hot and the diode puffed out white smoke. Would that be what killed it?

 

[Jay64]

Now I just read something that stated that the cathode, the side with the stripe, is the negative side, but that is the direction that the curent flows. So I should hook the diode up with the cathode to the lug marked + so that the current flows to the switch?

 

[TylerDurden]

The cathode should connect to the + lug.

The diode doesn't do anything until the contactor is de-energized... the coil has inductance and will release energy when the supply is cut (like an ignition coil).

 

[Jay64]

Well, I re-wired in another diode that works. I put the cathode (the side with the stripe) on the positive lug. I hooked up a 28v test battery. And I still get the same result. With the Key switch on and the kill switch in the run (open) position, I get the original battery voltage. With the key switch on and the kill switch in the off (closed) position, I get about half the original battery voltage. I tried it again with a 36v test battery, same result.
Does this contactor only work with the full 72v?
http://www.kellycontroller.com/shop/?mod=product&cat_id=12,28&product_id=189

How do you know when you just have a lemon of a contactor? Right now I don't have a 72 volt battery pack. Should I try to hook up two of my dewalt 36v in series? Will that blow my stock bms?

 

[TylerDurden]

Well, I re-wired in another diode that works. I put the cathode (the side with the stripe) on the positive lug. I hooked up a 28v test battery. And I still get the same result. With the Key switch on and the kill switch in the run (open) position, I get the original battery voltage. With the key switch on and the kill switch in the off (closed) position, I get about half the original battery voltage. I tried it again with a 36v test battery, same result.
Does this contactor only work with the full 72v?
http://www.kellycontroller.com/shop/?mod=product&cat_id=12,28&product_id=189

How do you know when you just have a lemon of a contactor? Right now I don't have a 72 volt battery pack. Should I try to hook up two of my dewalt 36v in series? Will that blow my stock bms?

Got any other 12V batts around? From cars or bikes? It won't look pretty with all sorts of batteries all over the place, but it should work.

The coil is not much different than a coil in a motor, at half voltage, you get only half the pulling power.

 

[Jay64]

I guess I was ordering too many things at once and didn't pay enough attention to everything. I contacted Kelly and they informed me that the contactor will only work at 72v. They said it might work at 60v, but it is designed to work at 72v. I bought the controller and contactor at the same time, the controller was able to handle a range of voltage, and I guess I just assumed that the contactor was the same way, but apparently it is not. I'm not going to run 72v for a while, so I guess I have to find a 48v one now.

I do have a few batteries that I could run in series to make 72v, I have 7 DeWalt packs, but will that be ok to run them in series in terms of the BMS?

 

[TylerDurden]

I do have a few batteries that I could run in series to make 72v, I have 7 DeWalt packs, but will that be ok to run them in series in terms of the BMS?

I can't say.

Doc's thread:

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=2339

If the answer is not there, you can PM him.

 

[Jay64]

Ok, I went ahead and tried it. I figured eventually I would be pulling the packs apart anyways, so I hooked two Dewalt battery packs in series and hooked it up to my wiring. SNAP! I accidently had the switches still on when I plugged in the battery and the contactor snapped to life. For a second I thought that it was an arc, so I jumped. I tested it out at 70v and I finally got the same voltage from when the kill switch was off as when the kill switch was on. 8) TD, thanks for all your help and walking me through it. Thanks for your patients.
So now I got another 48v contactor on order. Now it's on to working on the controller.

 

[TylerDurden]

I accidently had the switches still on when I plugged in the battery and the contactor snapped to life. For a second I thought that it was an arc, so I jumped.

:lol:

In medicine, they call that a "sentinel event": it's the one you survive, and hopefully remember later when you have the big stuff...

Party on...

 

[fechter]

Dang, I guess I missed what was going on here.

The first time it looks like the diode was in backwards and blew when the resistor smoked. It looks backward in the picture.

The other thing is the circuit needs the controller to be connected to work. The resistor slowly charges up the big capacitors in the controller. Juice from the caps is what energizes the coil. If the controller is shorted, the caps won't charge and the relay won't pull in. If the controller is not connected, the current from the resistor is not enough to pull in the contactor.

One thing to check is to make sure the controller isn't drawing any current when the resistor is trying to charge it up. If there's a drain present in the controller, then the resistor value must be decreased enough to get the required voltage on the caps.

On my Vego, I used a 24v contactor (relay), that I power from a small dc-dc converter. This allows me to change system voltage without changing the contactor. I suppose you could use a contactor with a 12v coil and use the main dc-dc converter for that as well as the lights.

 

[Jay64]

Fechter, yeah, the diode was in backwards when I got the puff of white smoke, and then again later. But I understand how it works now and have it hooked up correctly.
When I decided what parts I was going to use, I didn't realize that the conctactors were only one specific voltage. I figured I would get one higher then what I was planning on using so that I could build up to it. Now I see the mistake in that. I agree that it would be worth it to get a dc-dc converter to run one contactor but still be able to change the system voltage. Good idea, I hadn't looked at it that way, but now it makes total sense. The 12v idea might be worth it too so that I can also use the lights. Hmm, I'll have to think that, and possibly see if I can change my order to a 12v contactor and a converter. They aren't supposed to ship it out until Monday, so maybe they will be willing to change the order since it will be for more stuff.

 

[TylerDurden]

The other thing is the circuit needs the controller to be connected to work. The resistor slowly charges up the big capacitors in the controller. Juice from the caps is what energizes the coil. If the controller is shorted, the caps won't charge and the relay won't pull in. If the controller is not connected, the current from the resistor is not enough to pull in the contactor.

I guess that's easy enough to test: Jay can hookup the kelly and still use the SLAs and see if the caps can pull in the contactor.

In practice, the system will be 72V to the coil; it seems the resistor lets enough through to pull the switch closed, even without the controller attached.

:?

 

[Jay64]

yeah, that is what I was wondering about too. It appears, to me anyways (which could be totally wrong), that the contactor is working, even though I don't have the controller hooked up yet.

 

[fechter]

Maybe at the higher voltage, the resistor does pass enough current to operate the contactor.
If the controller was shorted, it would never get close to operating it, so the safety feature will still work. If the controller is disconnected and it operates, that's not really a problem.

 

[MidniteTweeker]

The little sheet metal bracket things.....

Aren't those used to mount the power resistor? Power resistor is hollow and supposed to get hot, so one end of the bracket stuffs into either end of the resistor, and the other end of the bracket bolts to a mounting surface. Keeps the hot resistor safely away from damaging anything, plus it's electrically insulated.

At least, I think that's how it works.

MT

 

[Jay64]

MT, thanks for the input on that. Seems to make sense to me.

 

[Jay64]

Ok, I ordered up another contactor, 48v. I finally got some time to try and wire it up and test if it works. I am using my 48v lifebatt pack which is reading 53v before the test. It seems like the contactor is not turning on again. On closer inspection of the contactor, is states 60v on it. At first I thought that maybe they sent me the wrong one and it isn't working because I'm not pulling 60v, just like my 72v contactor wasn't working until I pulled 72v. But I looked back at the invoice and it said 48-60v, so I'm thinking that isn't the problem. I double checked the diode, to make sure I had it hooked up the right way and that it wasn't burnt out. It still wasn't working. It is going back to the old thing of when the switches are on, it only get partial volts through to the end. I re-read through this thread to see if I might have missed something, and just saw fechter's post. Perhaps with this lower voltage, the contactor isn't working without the controller. I will try that now, if it isn't that, I'm not sure what to try next.

 

[Jay64]

Sweet. 8) Ok, I did a real fast connection to the controller (used some alligator clips to hold the wires on) and flipped the switches, and snap, the contactor engaged and I got the full volts at the controller. Once again Fechter was right. At the lower voltage, the controller does need to be connected. Man, I'm glad I hunted this thread back down, I was really banging my head against the wall there for a while. Now let's see if I can mock it up on the bike and connect the motor.