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Topic: 50 Amp Cable End (Read 606 times) previous topic - next topic

50 Amp Cable End

When I discovered that my inverter/charger was not charging house batteries, I also noticed that I was not getting electric power to the coach.  I looked at the coach-side end of the cable (female plug) and saw that one of the hot contacts was burned out. Looking at this plug with the neutral contact pointing down,
the socket on the right is the one that is fried.

I looked in my junk pile and found an old plug and that is damaged at the same place. What is causing this? I suspect that, after inserting the plug, I'm not twisting it far enough (or maybe twisting it too far).  Any ideas?

Appreciate your help and suggestions so I don't burn out another plug!

Thanks, Robert

P.S. Fortunately, I had ordered a new 50-amp cord from Amazon last week and it was delivered today.
Rob & Di
2001 U270 34'

Re: 50 Amp Cable End

Reply #1 –
Remove the coach receptacle and check the wires, you most likely have a loose connection.

The selected media item is not currently available.Bill&Doris 97 U270 36'
University of Parris Island Class of 66
Semper Fi  Build# 5174 MC#17094

Re: 50 Amp Cable End

Reply #2 –
Good idea, Bill.  Will have to wait until I return to our cabin where DP is kept.

Robert
Rob & Di
2001 U270 34'

Re: 50 Amp Cable End

Reply #3 –
The burnt twist plug (Hubbell-style) situation is exactly why we love our SmartPlug with its stronger electrical contacts and more secure attachment. 

All twist-plug installations would greatly benefit from conversion to SmartPlug.

RV Market - SmartPlug

Our SmartPlug installation is one of the most important safety improvements we have made. 

No more burnt plugs and no chance of fire from on overheated twistplug.

Re: 50 Amp Cable End

Reply #4 –
I think I have figured out why cord(s) failed.  Several years ago we replaced the coach receptacle but did not replace the cord plug. The coach receptacle still is shiny and looks like new. We don't use the coach much now but it is stored under our carport in front of my garage/workshop and is often moved in order to gain access to the shop. When doing this I usually disconnect the cord from the coach and replace it again when I'm finished in the shop. I think that this constant use had worn the damaged contact to the point of failure.

I like the idea of replacing the whole system with the modern one but as I now have a brand new cord and a good receptacle I think that should work for as long as we own the coach.

Thanks, Robert
Rob & Di
2001 U270 34'

Re: 50 Amp Cable End

Reply #5 –
Granted that age would cause arcing - thus the burnt contact points, but I would think that not switching off the power before connecting the power cord would contribute to arc burning,
In restless dreams I walked alone.
Narrow streets of cobblestone.


'93 U225
Build 4337
'14 CRV Toad

Re: 50 Amp Cable End

Reply #6 –
It seems one of the reasons for the twist plug arcing and burning is the points only make contact when the plug is fully rotated and then only with enough metal touching to handle 50-amps. 

The twist design does not 'lock' or 'latch' in this fully-rotated position and can over-time 'relax' from full-contact, allowing less metal to handle maximum amps. 

Also, the weight of the heavy cable and moving the cable even slightly seem to contribute to the un-rotation of the plug.

Smartplug is a designed to fully eliminate all the design limitations of the Hubble-type twist plug.  SmartPlug has over-sized contacts, secure insert and a 3-point "lock".  SmartPlug does not move or loosen.

Re: 50 Amp Cable End

Reply #7 –
Also, get yourself a tube of dielectric grease.  Everytime you plug in anywhere use the grease on both ends.  Coach and pedestal end.
John
John & Carm Morales

"We travel not to go anywhere, but to just go.  We travel for travel's sake.  Our great desire is to move."

Re: 50 Amp Cable End

Reply #8 –
Question:

Dielectric grease is  non-conductive, correct?  Can't use it on actual "prongs" or any conductive piece.  Only on non conductive surroundings?

That has been my understanding.  Coating a conductive piece, and getting it into conductive surfaces in campground pedestals would be bad - including for the next people hooking up.

 Or is that wrong?


Dan - Full timing since 2009
2003 U320 40' Tag 2 slide

Re: 50 Amp Cable End

Reply #9 –
Dan,
Dielectric grease is frequently used to separate different kinds of metals whose contact with each other causes a corrosive reaction.  It is used as a lubricant on rubber boots like those on spark plug wires. It is frequently used in crimp on connections to waterproof the connection and prevent corrosion.  I clean the contacts on my 50 amp plug and wipe a small amount of dielectric grease on them to prevent corrosion and arcing and make it easier to push the plug into the socket.  In general it should not be used on switch or relay contacts.

I use it on the plug from the toad to the coach to keep it from corroding.  The insulating properties are almost negligible.

There are electrically conductive greases such as this one which are used on battery posts and battery lugs to prevent corrosion and improve electrical contact.  I use this on all of my battery contacts.
NO-OX-ID "A Special" Conductive Terminal Grease

I am sure there are other opinions.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: 50 Amp Cable End

Reply #10 –
Quote from: AC7880 –
Question:

Dielectric grease is  non-conductive, correct?  Can't use it on actual "prongs" or any conductive piece.  Only on non conductive surroundings?

That has been my understanding.  Coating a conductive piece, and getting it into conductive surfaces in campground pedestals would be bad - including for the next people hooking up.

 Or is that wrong?


Dan,
You have a commonly found misconception.
It stems from the incorrect logic that the "dielectric" in "dielectric grease" means that the "dielectric grease" should only be used to insulate. All greases, dielectric or conductive, work by virtue of their low viscosity property which allows the grease to completely push out of metal to metal contact areas leaving essentially only metal-to-metal contact. Dielectric grease is just better at insulating high voltages that may otherwise be tempted to discharge over wide gaps or long paths.

Conductive greases and anti-seize compounds have a suspended base metal powder. The suspended metal powder contact area (in a proper made up electrical connection) is a tiny, tiny fraction of the area occupied by the insulating grease.  The grease does not conduct electricity in the tiny microscopic "pockets", but metal to metal contact in the connection actually conducts all of the electricity.  The grease simply fills the microscopic voids, which greatly aids in keeping moisture and conductive, as well as insulating, contaminants out of the metal to metal connection.

The working theory of "conductive" grease is when pressure is applied, the grease flows/squeezes out of the way. This leaves a fine metal powder that theoretically pierces some of the resident oxides as well as fills the microscopic voids that are always present. When making an electrical connection, the conductive grease is simply "squeezed out of the physical metal molecule to metal molecule contact area, thus carrying most of the suspended powder away. Any remaining powder is not enough to reliably reduce voltage drop across clamped connections.  But the grease greatly aids by filling all of the microscopic voids and thus keeping moisture and contaminants out of the connection.

Thus, when it comes to electrical connections, use dielectric (insulating) grease EVERYWHERE, especially on connections to campground pedestals, towed vehicle lighting plugs, circuit board external wiring (crimped-on-connectors), etc.  Corrosion-X works well for light coatings.  Auto parts store dielectric grease works well for slightly heavier coatings. 

When it comes to electrical current conduction paths, (NOT INSULATING PATHS) Conductive grease and Anti-seize compounds works well ONLY for high frequency, very high voltage, very low current connections and even then it needs to be very carefully applied to prevent just a fingerprint on an insulation boot from conducting inappropriately to earth or shield.
HTH,
Neal
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Neal (& Brenda) Pillsbury
'02 U320 SPEC, 4200, DGFE, Build #5984
'04 Gold Wing
'07 Featherlite 24'
'14 Jeep Grand Cherokee Summit
MC #14494
Exeter, NH & LaBelle FL
Quality makes the Heart Soar long after Price is Forgotten