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Melted battery contractor ground wire
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frank3
Guest

Posted: Mon Jul 05, 2021 12:49 pm Post subject: Melted battery contractor ground wire

I flipped the battery switch that activates the contractor this AM and melted the ground wire.



I'm deep in the process of wiring my RV7 (most of the wiring completed), using a legacy schematic with EBUS architecture.  Wiring to the battery contractor is standard--wire from contactor to switch (2-10) with ground to field of tabs at firewall.



I have used a lawn tractor battery numerous times to energize the system when testing components as they're installed.  All has worked well until this AM.



I'd appreciate input to help me resolve what the issue might be.



Thanks much in advance.

frank3
Guest

Posted: Mon Jul 05, 2021 1:36 pm Post subject: Re: Melted battery contractor ground wire

It might be pertinent to mention I did not hear the typical "clank" from the battery contractor when I flipped the switch.

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Mon Jul 05, 2021 3:21 pm Post subject: Re: Melted battery contractor ground wire

Have you made any wiring changes to the battery contactor recently?

It seems that the melted wire is connected to positive someplace. 

One possibility is a shorted contactor coil, but unlikely.

_________________
Joe Gores

frank3
Guest

Posted: Tue Jul 06, 2021 4:50 am Post subject: Re: Melted battery contractor ground wire

I haven't made any changes to the battery contactor recently.

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Jul 06, 2021 6:17 am Post subject: Re: Melted battery contractor ground wire

Remove the wire from the small terminal of the battery contactor.

Measure the resistance between that small contactor terminal and the large contactor terminal that connects to battery positive. 

 I expect it to be about 20 ohms.  If less than 5 ohms, the contactor coil is shorted.

_________________
Joe Gores

frank3
Guest

Posted: Tue Jul 06, 2021 9:39 am Post subject: Re: Melted battery contractor ground wire

Thanks Joe.  Did that this AM.  No resistance at all.  Shorted contactor as you suggest.



The burnt ground wire was in a loose bundle--run together but haven't tied them together.  I assume there's possible damage to other wires in the bundle?  If there's no damage to the insulation of the other wires then they're good to go?

frank3
Guest

Posted: Tue Jul 06, 2021 10:20 am Post subject: Re: Melted battery contractor ground wire

This experience makes me wonder why no circuit protection for the contactor activator switch circuit in any of the architectures.



Maybe it's because a short in the contactor is unlikely, as Joe says, but isn't that the assumption behind all circuits that do have circuit protection built in?

jluckey(at)pacbell.net
Guest

Posted: Tue Jul 06, 2021 12:16 pm Post subject: Melted battery contractor ground wire

Hello Frank,





You are asking good questions.

What typically happens is the coil burns up and causes an open circuit, but in your case it appears to have failed closed.



It will be interesting to conduct a post-mortem on it to determine how it created such a hard fault.

Questions:

1. Can you post a picture of the master solenoid/contactor?

2. What size wire runs from the solenoid to the master switch?





-Jeff



                  

                                                                    On Tuesday, July 6, 2021, 11:27:49 AM PDT, frank3 <frank3phyl(at)comcast.net> wrote:                 

                 



                 



                 --> AeroElectric-List message posted by: "frank3" <frank3phyl(at)comcast.net (frank3phyl(at)comcast.net)>



This experience makes me wonder why no circuit protection for the contactor activator switch circuit in any of the architectures.



Maybe it's because a short in the contactor is unlikely, as Joe says, but isn't that the assumption behind all circuits that do have circuit protection built in?



--------



Frank McDonald



Kitfox S7 - sold



RV7 in progress



Acworth, GA



Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=502723#502723



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frank3
Guest

Posted: Tue Jul 06, 2021 4:25 pm Post subject: Re: Melted battery contractor ground wire

Jeff

What pic would be most revealing for you?  Installed on the firewall?  Removed on the bench?  Other?

jluckey(at)pacbell.net
Guest

Posted: Tue Jul 06, 2021 4:49 pm Post subject: Melted battery contractor ground wire

I'd like to see it as installed, for starters.





-Jeff



                  

                                                                    On Tuesday, July 6, 2021, 5:32:06 PM PDT, frank3 <frank3phyl(at)comcast.net> wrote:                 

                 



                 



                 --> AeroElectric-List message posted by: "frank3" <frank3phyl(at)comcast.net (frank3phyl(at)comcast.net)>



Jeff



What pic would be most revealing for you?  Installed on the firewall?  Removed on the bench?  Other?



--------



Frank McDonald



Kitfox S7 - sold



RV7 in progress



Acworth, GA



Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=502729#502729



http://forums.matronics.comp;       - NEW MATRONICS LIST WIKI -



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DougW

Joined: 16 Sep 2015
Posts: 14
Location: Washington

Posted: Tue Jul 06, 2021 6:09 pm Post subject: Melted battery contractor ground wire

Frank, 



The only way you are going to melt that wire is likely with a direct short

between positive and negative battery voltages.  Most likely candidates for

that occurrence is a mis-wired switch or contactor.



I would disconnect the wire from the switch where it attaches to the 'field

of tabs' and rewire from the switch to the contactor.  Do a continuity test

from the contactor terminal to the now disconnected connector at the field

of tabs.  In the switch 'ON' position, you should have very little

resistance, and high resistance in the 'OFF' position.  If both of those are

TRUE, then that wiring should be OK.  If they are not both TRUE, then you

need to examine the wiring to the switch more closely.



Another possibility is that you have the positive and negative terminals of

the contactor switched with your wiring arrangement.  That is the area I

would examine next after all the foregoing.  If neither of these is the

problem, could it be a bad contactor?



Doug Windhorn



--

nuckollsr

Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS

Posted: Wed Jul 07, 2021 5:52 am Post subject: Re: Melted battery contractor ground wire

At 09:08 PM 7/6/2021, you wrote:



--> AeroElectric-List message posted by: "n1dw" <n1deltawhiskey>



Frank, 



The only way you are going to melt that wire is likely with a direct short

between positive and negative battery voltages.  Most likely candidates forthat occurrence is a mis-wired switch or contactor.



  Question: did this contactor installation EVER work?



  Q: What is the measured resistance of the contactor's

     coil? . . . WITH ANY SPIKE SUPPRESSION DIODE

     REMOVED.



  Q: Is there ANY continuity between the any terminal

     of contactor and it's case?



  Q: What kind of contactor is this? 3-terminal, 4-terminal?



  Q: Is there a spike suppression diode installed across

     the contactor's coil terminals. Has this been checked

     for proper polarity? (Banded end needs to fact the battery,

     other end faces master switch). If this diode is BACKWARDS

     or SHORTED it will cause failure of the contactor-to-master

     switch wire. If a backwards diode is found to be root

     cause of the burned wire, then replace BOTH diode

     and wire. The current impressed on the diode during

     wire-burning will have exceeded its ratings and

     it's probably toast too.

frank3
Guest

Posted: Wed Jul 07, 2021 3:09 pm Post subject: Re: Melted battery contractor ground wire

Folks, I posted some erroneous info.  When I measured the resistance between the small contactor terminal and the larger terminal connecting to the battery (+) I did so with the diode in place.  Hence, the "no resistance".  (I'm still learning or at least trying to)



Today I removed the contactor, removed the diode from the contactor, and checked for resistance, again.  This time I got 0.016 ohms.  So, according to Joe's criteria, it's still a bad contactor.  Guess we ended up at the same place using a different path?



Just for kicks, I did a bench test.  I connected a 22 awg wire to the small terminal, terminating at the the master switch (2-10).  Using a similar wire I connected to the switch terminating at neg side of contactor.  I applied jumper cables to the large contactor terminals.  I activated the switch and then connected the jumper cables to the battery.  Same result--wires melted.



Tried to attach pic of the contactor on the firewall but unable to reduce the pic file size.



Joe asked what size wire I used.  18 awg contactor to master switch; 22 awg to field of tabs.  I can not recall whay I used the 18 awg instead of 22 awg.  The 18 awg survived the event.  The 22 awg melted, as a fussible link for the 18 awg?



Bob, if you still want the contactor I'll gladly send it to you.  Just let me know where to send.



Thanks everyone for you interest and advice.  I have ordered a new contactor from our friends at B&C.

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Wed Jul 07, 2021 3:47 pm Post subject: Melted battery contractor ground wire

On 7/7/2021 6:09 PM, frank3 wrote:

 	  Quote: 	
		   



 Folks, I posted some erroneous info.  When I measured the resistance between the small contactor terminal and the larger terminal connecting to the battery (+) I did so with the diode in place.  Hence, the "no resistance".  (I'm still learning or at least trying to)



 Today I removed the contactor, removed the diode from the contactor, and checked for resistance, again.  This time I got 0.016 ohms.  So, according to Joe's criteria, it's still a bad contactor.  Guess we ended up at the same place using a different path?



 Just for kicks, I did a bench test.  I connected a 22 awg wire to the small terminal, terminating at the the master switch (2-10).  Using a similar wire I connected to the switch terminating at neg side of contactor.  I applied jumper cables to the large contactor terminals.  I activated the switch and then connected the jumper cables to the battery.  Same result--wires melted.



 Tried to attach pic of the contactor on the firewall but unable to reduce the pic file size.



 Joe asked what size wire I used.  18 awg contactor to master switch; 22 awg to field of tabs.  I can not recall whay I used the 18 awg instead of 22 awg.  The 18 awg survived the event.  The 22 awg melted, as a fussible link for the 18 awg?



 Bob, if you still want the contactor I'll gladly send it to you.  Just let me know where to send.



 Thanks everyone for you interest and advice.  I have ordered a new contactor from our friends at B&C.



 --------

 Frank McDonald

 Kitfox S7 - sold

 RV7 in progress

 Acworth, GA

That doesn't 'sound' right. There should be 2 'fat' terminals and one 
	


small terminal on a typical master contactor. With no voltage applied, 

you should measure open circuit (infinite resistance) between the small 

terminal and one of the fat terminals,  some relatively low (but not 

close to zero; see Joe's resistance number) resistance between the small 

terminal and the other fat terminal, and   infinite resistance between 

the 2 fat terminals.



Measuring .016 ohms with a typical ohm meter sounds a little suspicious; 

there's often more resistance than that in the leads and terminal 

contact points.



Did you have it hooked up as shown in this video?

https://www.youtube.com/watch?v=7FSK1JblQaE

Near the end, he shows how to hook up a 4 terminal version (less common).



Charlie



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_________________
Charlie

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Wed Jul 07, 2021 4:30 pm Post subject: Re: Melted battery contractor ground wire

Frank, I interpreted your post to mean that you connected one jumper cable from battery positive to a fat terminal on the contactor,

and you connected another jumper cable from the negative battery terminal to the other contactor fat terminal.

If that is true, then you are lucky that the contactor is defective.  There could have been flying molten metal.

The negative battery terminal should NOT be connected to a fat contactor terminal because something bad will happen.

_________________
Joe Gores

frank3
Guest

Posted: Thu Jul 08, 2021 8:40 am Post subject: Re: Melted battery contractor ground wire

Bob's questions answered:



1.  Yes, the contactor has been functioning for a couple of months.  I've been using jumper cables to connect a lawn tractor battery so I can test components as they are installed.



2.  The measured resistance is 16.5 ohms, small terminal to battery side fat terminal with diode removed.  (The 0.016 value reported and questioned by Charlie was using the wrong range).



3.  There is no continuity between any of the terminals and the case.



4.  This is a three terminal Cole Hersee provided by Vans Aircraft.



5.  There was a spike supression diode installed, provided by Vans with terminals and shrink tube insulation already installed.  I peeled back the insulation to ensure the diode was installed properly, with the band towards the fat terminal.  As you suggested, the diode is now nonfunctional.



Bob, the contactor is in the mail.



As Doug suggested (6 Jul #11) I went through the suggested process to test the wiring and switch.  Both were TRUE--both wiring and switch were proper.



BTW, I don't understand how a miss-wired switch could cause a direct short.  My understand is the switch simply enables the circuit to conduct current or not.  I can see the possibility of a short between the switch and the airframe but don't understand miss-wiring.  Something I need educating about?



Jeff, I submitted the pic with contactor installed.  We'll see if it gets published.



Joe (7 Jul #5), you interpreted my post correctly.  After reviewing schematics I see I WAS lucky!  (Might just as well connected the two jumper cables!!!  Just talking to myself)



Charlie (7 Jul #4), thanks for suggesting the video on battery contractors.  It was wired per the video.  What you describe re:  open circuits & resistance between the terminals is what I was getting.  I must not have described clearly.  And, as stated above, you were right to be suspicious of my #, I used the wrong range.



Again, thanks to all for their interest, questions, and suggestions.

frank3
Guest

Posted: Thu Jul 08, 2021 8:55 am Post subject: Re: Melted battery contractor ground wire

Don't know if this is relevant but checked the fuses to all the circuits and found the 5amp fuse to the Dynon EFIS was blown.  EFIS was only open circuit at the time of the incident.  Evidence there must have been some kind of over voltage event, I guess.



New fuse and using EBUS circuit I found the EFIS is good to go.

jluckey(at)pacbell.net
Guest

Posted: Thu Jul 08, 2021 9:06 am Post subject: Melted battery contractor ground wire

Is it possible that you inadvertently hooked-up the battery backwards that day?

                  

                                                                    On Thursday, July 8, 2021, 10:02:12 AM PDT, frank3 <frank3phyl(at)comcast.net> wrote:                 

                 



                 



                 --> AeroElectric-List message posted by: "frank3" <frank3phyl(at)comcast.net (frank3phyl(at)comcast.net)>



Don't know if this is relevant but checked the fuses to all the circuits and found the 5amp fuse to the Dynon EFIS was blown.  EFIS was only open circuit at the time of the incident.  Evidence there must have been some kind of over voltage event, I guess.



New fuse and using EBUS circuit I found the EFIS is good to go.



--------



Frank McDonald



Kitfox S7 - sold



RV7 in progress



Acworth, GA



Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=502753#502753







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Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Thu Jul 08, 2021 9:42 am Post subject: Melted battery contractor ground wire

My 1st thought, as well. That would       explain smoking the spike suppression diode on the contactor. Must       have been God's Own suppression diode, though, to take the wire       with it.

       

       Charlie

       

       On 7/8/2021 12:06 PM, Jeff Luckey wrote:

     

      	  Quote: 	
		                         Is it possible that you           inadvertently hooked-up the battery backwards that day?

         

         

       

                            On Thursday, July 8, 2021, 10:02:12 AM PDT, frank3             <frank3phyl(at)comcast.net> (frank3phyl(at)comcast.net) wrote: 

           

           

           

           

                        --> AeroElectric-List message posted by:               "frank3" <frank3phyl(at)comcast.net (frank3phyl(at)comcast.net)>

             

             

             

             Don't know if this is relevant but checked               the fuses to all the circuits and found the 5amp fuse to               the Dynon EFIS was blown.  EFIS was only open circuit at               the time of the incident.  Evidence there must have been               some kind of over voltage event, I guess.

             

             

             

             New fuse and using EBUS circuit I found the               EFIS is good to go.

             

             

             

             --------

             

             Frank McDonald

             

             Kitfox S7 - sold

             

             RV7 in progress

             

             Acworth, GA

             

             

             

             

             

             

             

             

             

             Read this topic online here:

             

             

             

             http://forums.matronics.com/viewtopic.php?p=502753#502753

             

             

             

             

             

             

             

             

             

             

             

             

             

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_________________
Charlie

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Thu Jul 08, 2021 9:59 am Post subject: Re: Melted battery contractor ground wire

I think that jluckey has solved the problem.  Reverse battery polarity explains the melted wire and the blown fuse.  Luckily the EFIS was not damaged.

I predict that Bob N will not find anything wrong with the contactor.  An  over voltage event is extremely unlikely without an alternator running.

It is pretty easy to reverse battery voltage when using jumper cables.  One has a 50-50 chance of getting it wrong.

_________________
Joe Gores

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