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Scary issue with Nema 14-50 adapter melting

Peter_M

Member
Oct 10, 2013
975
290
Ottawa, Canada
I was thinking of putting a thin coat of conductive grease on all the plugs I use - HPWC and UMC to car (with a cotton swab in the large contacts in the handle), adaptors to UMC and adaptors to wall receptacles. I could also put some on the cable ends where they connect into the HPWC and the breaker for a better connection there.

Good idea? The only downside I can think of is if you get some grease in the wrong place it could cause a short, so you'd have to be very careful applying it. Plus it's black so it could get a bit messy...
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Mar 8, 2012
19,588
22,077
Texas
I was thinking of putting a thin coat of conductive grease on all the plugs I use - HPWC and UMC to car (with a cotton swab in the large contacts in the handle), adaptors to UMC and adaptors to wall receptacles. I could also put some on the cable ends where they connect into the HPWC and the breaker for a better connection there.

Good idea? The only downside I can think of is if you get some grease in the wrong place it could cause a short, so you'd have to be very careful applying it. Plus it's black so it could get a bit messy...

There's not a lot of easily accessible material outside of the manufacturer's web sites (and some of them are very promotional or not very informative). I also went though a bunch of forums and here's the one that I thought had the best post--even though it's on an audio site.

It's also not as much of a phase problem as a noise problem. We are just using the two legs of your electrical drop to isolate the stereo stuff from noise producing components like flourescent lights and dimmers.

To make this happen, you may need to call an electrician to re-wire your box. I did. I'd recommend he use silver conductive grease on the breakers' contacts and every connection from then on, to the socket in the wall. I continued further down the electrical path, using silver conductive grease on my home-made 10 gauge power wires using Wattgate plugs and sockets.

I bought a little tub, 0.5 oz. Here are three choices of where to get the stuff:

It's expensive at $60-90 but what I bought should last me a lifetime.

Be careful applying this grease. It sticks to your hands and gets all over everything. It is liquid wire and very conductive. You can create a short in no time so clean up any reside with something like Goo-Gone.

One last thing: If your breakers are more than a year or two old, I'd recommend replacing the them with new ones. Breakers are cheap. And they do corrode. As long as you are going to the expense of wiring up your stereo correctly, put in new breakers.

ggergm, Jan 16, 2013

The "sticks to your hands" part makes me think it's not really what you want on the UMC as it will probably make a mess when you take your UMC traveling. If you have two UMCs then only the stationary one gets it. However because your likely to never remove the 14-50 adapter from the UMC, bending the pin won't be an issue. Should be fine for the HPWC--assuming there's no other reason not to use it. FlasherZ, you want to chime in? This is your area.
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,866
Toronto, ON
I was thinking of putting a thin coat of conductive grease on all the plugs I use - HPWC and UMC to car (with a cotton swab in the large contacts in the handle), adaptors to UMC and adaptors to wall receptacles. I could also put some on the cable ends where they connect into the HPWC and the breaker for a better connection there.

Good idea? The only downside I can think of is if you get some grease in the wrong place it could cause a short, so you'd have to be very careful applying it. Plus it's black so it could get a bit messy...

I don't really thing that is intended to improve the connection. We in the utility industry use it a lot when plugging electricity meters into the meter base, but not for electrical reasons. It's so the meter can be removed years later without yanking the socket lugs out if/when they corrode together.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
The "sticks to your hands" part makes me think it's not really what you want on the UMC as it will probably make a mess when you take your UMC traveling. If you have two UMCs then only the stationary one gets it. However because your likely to never remove the 14-50 adapter from the UMC, bending the pin won't be an issue. Should be fine for the HPWC--assuming there's no other reason not to use it. FlasherZ, you want to chime in? This is your area.

The only place I've ever used conductive grease is for low-voltage special applications, like maintaining ground continuity on tilt-bed trailers and such. mknox brings up a good use as well, although as he says it's to prevent meters from being corroded/welded to the sockets (which is a very dangerous condition).

I've never used it on high-current applications, and I'd probably suggest that in this particular case, it might provide only temporary relief. The heat generation is caused by a reduction in conductor surface area - either corrosion or a loose coupling between the adapter and the head of the UMC plug; it's likely that the grease would help to maintain current-carrying capacity to a certain extent, but even if so, if the grease becomes a considerable part of the current-carrying capacity it will create heat itself.

What Tesla needs to determine is whether it's corrosion, pin misalignment/bending/etc., or even pin size causing this heat across multiple UMC's. A touch of the grease might solve corrosion issues and ensure continuity, but it won't solve the other two problems.

The trade-off is probably not worth it, IMO.
 

ThosEM

Space Weatherman
Dec 13, 2013
869
309
Annapolis, MD
Has Tesla determined a cause yet? I have just had a look at mine, which has had no heat issues in the first three weeks, charging for a few hours at a full 10 kW. The pins are amazingly small for that amount of power, even if the NEMA 14-50 pins may be a bit of overkill. The contrast in pin size and shape is pretty stark.

I wonder if, as someone speculated, a bit of dog hair or other tiny debris or contamination could break the cylindrical sliding joint between pin and sleeve enough to increase its resistance and cause these events? Failure to fully seat the adapter on the UMC connector could clearly cause issues, especially if bending the latch mechanism cause it to get in the way. It seems important to track down the root cause of these meltdowns, because the system does work nominally if everything is right, and there are a lot of folks out there, like me, who need to know how to avoid this. Having a smoke alarm is very small comfort.

I have never seen or felt for evidence that the inline box is getting warm. My attitude toward spending a grand on a wall mounted hard wired EVSE for everyday, was "why bother"? This will force me to think about it, though I might worry that would just introduce more wiring joints about which to be concerned. I think I'd prefer a portable unit that is bulletproof, but the first time I leave the UMC behind when heading out on a trip for which I'll need it, I may shell out for the fixed wall unit so I can keep it in the boot.


To me, those pins where the adapter meets the charger cable are quite small for continuous 40 amp current flow day in and day out. Not to mention how hot the inline "box" gets at that level of charging. My UMC stays in the trunk for occasional use and I use a wall mounted hard-wired EVSE for everyday charging.

If you are going to use the mobile connector to charge every day, I would suggest dialing down the current flow just a little bit on the screen to 25 amps or so to reduce heating effects...I know a lot of people are successfully using these every night to charge, but this isn't the first time we've seen melting in the adapter area. I think its easy to take for granted the fact that almost 10,000 watts can flow through that small device and connector / adapter...
 

howardc64

Member
Oct 19, 2013
170
73
Seattle
My UMC's NEMA 14-50 adapter and insertion into a 14-50 extension cable is snug tight. However, the short cable from the UMC to the plug has the highest temperature during charging. Not hot but quite warm. The 14-50 adapter is just a little warm and where it plugs into the extension cord and the extension cord itself is cool to the touch.

To maximize safety. I just dial down the charging rate to 30A. This reduces to ~25mph (I thought thats what I saw and not sure why its higher than J1772 30A at 19mph) and the short cable is much cooler. I figure with this lower amp draw and Tesla's updated firmware to reduce another 25% amp draw if fluctuation is detected, I should be pretty safe on this charging circuit. This charging rate replenish the 75 miles range my wife use each day with 3-4 charge time per night.

Will install a heat detector over the whole UMC area soon for added safety.
 

rlang59

Member
Feb 27, 2013
945
30
US
My UMC's NEMA 14-50 adapter and insertion into a 14-50 extension cable is snug tight. However, the short cable from the UMC to the plug has the highest temperature during charging. Not hot but quite warm. The 14-50 adapter is just a little warm and where it plugs into the extension cord and the extension cord itself is cool to the touch.

To maximize safety. I just dial down the charging rate to 30A. This reduces to ~25mph (I thought thats what I saw and not sure why its higher than J1772 30A at 19mph) and the short cable is much cooler. I figure with this lower amp draw and Tesla's updated firmware to reduce another 25% amp draw if fluctuation is detected, I should be pretty safe on this charging circuit. This charging rate replenish the 75 miles range my wife use each day with 3-4 charge time per night.

Will install a heat detector over the whole UMC area soon for added safety.

The voltage at the J1772 30A is probably 208V vs the ~240V where you plug in the UMC.
 

Alexander

P# 8,878
Oct 9, 2012
295
43
Valencia, CA
You can not go to mass market one day and hope folks will be always do things the 100% correct way to prevent such an issue. It needs to be engineered in such a fashion to mitigate that risk as much as humanly possible. Or if not possible eliminate that as a recommended way to charge the vehicle.

I agree with this. You have to make certain things "idiot proof." Not saying that anyone is an idiot, just that a lot of people have ZERO clue about how this technology works. You have to help those people help themselves by making it impossible for them to do the wrong thing. Not saying anyone did the wrong thing, just saying that they shouldn't have the ability to do the wrong thing in the first place.

I'm going to move my smoke detector in the garage closer to the outlet...

I'm going to put one in my garage today as apparently I don't have one in there now.
 

afilm_guy

Member
Jun 11, 2012
20
0
North San Fernando Valley
Let us start near the beginning.

A few assumptions we need to make.
This is most likely the largest appliance we leave running/"consuming electricity from the wall"
while we are most likely sleeping.

This by itself should be alarming.

One should ask why didn't we put safety equipment like smoke detectors
as a requirement for installation of charging equipment.

A garage fire could likely lead to loss of life!

Okay there are some alarming thoughts.

I received my car in November of 2012
I sent correspondence and contacted the factory by phone.
To alert them I thought this charging equipment UMC was under size
to run at full rated power in the public's homes.
And should be addressed before mass-market adoption.
You would think a signature owner could influence the development of this automobile.
We find ourselves very frustrated knowing a lot of this could be avoided.
Tesla appears to be taking the shortest route to try and rectify
the reports coming out of the media.

This is unfortunate real engineering is not being looked at.
I encourage all UMC users to install smoke detectors.
I have taken my own advice and have installed smoke detectors.

I would also recommend an electrician visit the home
and verify good torque on connection fasteners socket and circuit breaker.
At least once after initial installation.
If you observe your utility changing a meter you will see them re-torque the connections.

If you have a good understanding of electricity
I'd recommend you perform your own test.

Run the UMC at 40 Amp @240v for 15 minutes.
Disassemble and acknowledge where the heat build up a starting.

Let us as the concerned community
help Tesla solved this problem before it gets completely out of hand.
We all need to raise our hands and say stop the Band-Aids.

Some of the cautions are prudent but they're not the whole solution.
There is a fundamental connection problem with the UMC
that is not being addressed.
Should we petition for a proper recall of the entire UMC charging cable assembly..

And layout safety precautions for the other things that can cause
destructive heeding of this UMC charging assembly.
It would be prudent with the connection like this to a high-powered appliance
that will have the opportunity to be plugged in and out by the general public.

Shouldn't there be a big yellow tag linking safety precautions with this high-powered
connection to the wall?

If the car detects the UMC is being used,
should a safety screen be presented
to remind the non-technical folks how important
plugging this equipment in properly is essential.
And could result in catastrophic harm if not done so.
How do we help the non-technical understand how to work with this technology?

Remember this thing is running at full power
while the user is most likely asleep on a regular basis.

Even if there was no local heating happening in the connector junction,
it would be prudent to recommend some safety precautions and alert systems.
When the home wiring turns out to be questionable.

Does anyone have heat diagnostic photography equipment, that are group could leverage
to visually show what's going on a thermal photograph would be worth a thousand words.

What do you thimk?

lead sleeping dogs lie, or address the fundamental problem.

I don't believe a cable set provided with the automobile should produce substantial heating
when being used at specification.
 

brianman

Burrito Founder
Nov 10, 2011
17,521
2,989
Anyone receive new 14-50 adapters from TM yet? I read all the articles saying they are coming but I haven't received one yet.
I was told by both the Bellevue service center (phone) and Fremont service center (in person) that the adapters haven't arrived but that they will be shipped directly to owners rather than distributed via the service centers. Neither had anything to say about 6-50 yet.
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Mar 8, 2012
19,588
22,077
Texas
I believe that non-reversable heat sensing tape would be a better prevention method than a smoke detector because a developing problem would be noticed long before it got to the smoking point. The problem doesn't happen overnight, it slowly builds up over weeks or months.
 

Rainbow

Member
Nov 22, 2013
79
0
USA
I believe that non-reversable heat sensing tape would be a better prevention method than a smoke detector because a developing problem would be noticed long before it got to the smoking point. The problem doesn't happen overnight, it slowly builds up over weeks or months.
I would recommend both. There may not always significant heating in prior uses to catastrophic failure.

I think both heat tape and smoke alarms are good precautions.
 

wycolo

Active Member
May 16, 2012
3,068
423
WA & WY
Look at the massive size of the 14-50 plug/socket connectors. The public can inspect it, clean it and in general understand if it is functioning properly. UL/CSA approved. 'Good' technology.

Look now at the intermediate plug between the UMC and the several adapters: tiny, hard to inspect, and near impossible to sense if the contacts are actually connecting properly as they are being pushed together. NOT UL/CSA approved. 'Bad' technology.

Better to have built the UMC with only the 14-50 plug on the cable end. Then each adapter would have a 14-50 socket going into the various (approved) plugs. UL/CSA might even have approved such a UMC.

My UMC stays in the trunk. I've only used it twice at campgrounds being careful to feel the adapter for any internal heat generation, and remaining at the car during charging.

Most daily UMC users have it between a 14-50 outlet and MS parked in favorite spot. They never carry it in the car either. So they should solder or spot-weld a new cable to the UMC side of the adapter and put a new 14-50 plug on the other end which plugs into the wall outlet. Thus they have eliminated the unsafe adapter plug/thingy. Problem solved. No need to $pring for the HPWC since the UMC unit itself, and its cable/plug into the MS, has a good reliability experience so far.
--
 
Last edited:

Rainbow

Member
Nov 22, 2013
79
0
USA
Look at the massive size of the 14-50 plug/socket connectors. The public can inspect it, clean it and in general understand if it is functioning properly. UL/CSA approved. 'Good' technology.

Look now at the intermediate plug between the UMC and the several adapters: tiny, hard to inspect, and near impossible to sense if the contacts are actually connecting properly as they are being pushed together. NOT UL/CSA approved. 'Bad' technology.

Better to have built the UMC with only the 14-50 plug on the cable end. Then each adapter would have a 14-50 socket going into the various (approved) plugs. UL/CSA might even have approved such a UMC.
If safety really was Tesla's a top priority, I would think they would have used UL/CSA approved charge connections.

In my opinion Tesla has skimped on the adapters and many of the connections. I think they are insufficient for the amount of current that they potentially expected to carry.

My UMC stays in the trunk. I've only used it twice at campgrounds being careful to feel the adapter for any internal heat generation, and remaining at the car during charging.
I would hope that people would periodically charge at a high rate for half an hour more and then feel the charge connections for excessive heating, then typically reduce the charge rate for an added margin of safety. I would also recommend periodically inspecting connectors for signs of overheating, melting and burning (and other problems dirt, corrosion, etc.).

Most daily UMC users have it between a 14-50 outlet and MS parked in favorite spot. They never carry it in the car either. So they should solder or spot-weld a new cable to the UMC side of the adapter and put a new 14-50 plug on the other end which plugs into the wall outlet.
Soldering can be a double-edged sword. Soldering can wick up wires, which can make wires more vulnerable to mechanical fatigue (not good for wires that are moved a lot). In some cases soldering can reduce surface area, which could reduce current carrying capacity.

Spot welding is generally good, however I have seen many (non-Tesla) Chinese connectors fail because of inferior welds, and because manufactures in part assumed that they could skimp on materials and designs because the connections were spot welded. There were a lot of fires and recalls because they skimped on designs and materials.
 

afilm_guy

Member
Jun 11, 2012
20
0
North San Fernando Valley
Look at the massive size of the 14-50 plug/socket connectors. The public can inspect it, clean it and in general understand if it is functioning properly. UL/CSA approved. 'Good' technology.

Look now at the intermediate plug between the UMC and the several adapters: tiny, hard to inspect, and near impossible to sense if the contacts are actually connecting properly as they are being pushed together. NOT UL/CSA approved. 'Bad' technology.

Better to have built the UMC with only the 14-50 plug on the cable end. Then each adapter would have a 14-50 socket going into the various (approved) plugs. UL/CSA might even have approved such a UMC.

My UMC stays in the trunk. I've only used it twice at campgrounds being careful to feel the adapter for any internal heat generation, and remaining at the car during charging.

Most daily UMC users have it between a 14-50 outlet and MS parked in favorite spot. They never carry it in the car either. So they should solder or spot-weld a new cable to the UMC side of the adapter and put a new 14-50 plug on the other end which plugs into the wall outlet. Thus they have eliminated the unsafe adapter plug/thingy. Problem solved. No need to $pring for the HPWC since the UMC unit itself, and its cable/plug into the MS, has a good reliability experience so far.
--
I wanted to thank you For articulating this clearly!

If the Tesla organization does not address this issue to my satisfaction,
I will likely publish a how-to document to cut off the intermediate adapter plug.
And attach a 14-50 plug with the proper resister signaling required to make it work.

It's unfortunate they made something that looks so good,
that doesn't really work well.

I believe the corrective actions they are taking
in combination with removing the intermediate connection would be the right solution.
 

Peter_M

Member
Oct 10, 2013
975
290
Ottawa, Canada
I'm not sure if this has been suggested before, but what would make sense to me is to have a "UMC generation 2" that has a hardwired 14-50 plug (for the highest current and most common usage), and then provide adaptors from 14-50 "down" to 14-30, 5-15, etc.

It would need some way to tell the UMC (and the car) what kind of adaptor is connected. Maybe the 14-50 plug could have a little physical sliding switch switch that moved a hole facing the adaptor, and the adaptors would have plastic pins facing the 14-50 that would need to fit into that hole. So you'd switch the UMC 14-50 plug to "30" and then plug it into the 14-30 adaptor. in the "50" position, there would be no hole, so you couldn't attach any adaptor. Or have an extra low-voltage electrical connection between the 14-50 plug and the adaptors (like today's UMC) but do it in a way that the 14-50 plug can be used on its own. Or maybe carry a signal on the actual power pins, like they do with X-10... I'm sure they could find a way.

And if all that turns out to be too difficult, make another proprietary connector that's "beefier" than the current UMC one.
 

efusco

Moderator - Model S & X forums
Mar 29, 2009
5,421
666
Nixa, Missouri, United States
It would need some way to tell the UMC (and the car) what kind of adaptor is connected. Maybe the 14-50 plug could have a little physical sliding switch switch that moved a hole facing the adaptor, and the adaptors would have plastic pins facing the 14-50 that would need to fit into that hole. So you'd switch the UMC 14-50 plug to "30" and then plug it into the 14-30 adaptor. in the "50" position, there would be no hole, so you couldn't attach any adaptor. Or have an extra low-voltage electrical connection between the 14-50 plug and the adaptors (like today's UMC) but do it in a way that the 14-50 plug can be used on its own. Or maybe carry a signal on the actual power pins, like they do with X-10... I'm sure they could find a way.

And if all that turns out to be too difficult, make another proprietary connector that's "beefier" than the current UMC one.
You don't really even need that. The pilot signal to the car allows the car to determine the available current. I have a plethora of adapters I use and a NEMA 14-50 extension cord, the car can figure it out the majority of the time.
 

afilm_guy

Member
Jun 11, 2012
20
0
North San Fernando Valley
This is from another post


Please don't hack off the UMC's wall plug socket without understanding that there is a fourth control pin with the following resistance values to ground:

Tesla UMC Plugs Resistance

40 amps - 9.08k ohms

24 amps - 33.16k ohms

16 amps - 75k ohms

12 amps - 140k ohms
 

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