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Plug Adapter on my Universal Mobile Connector has melted...

Lyon

2016 S P100DL, 2016 X P90D
Dec 26, 2011
2,004
215
Eugene, Oregon
Mine got melts tonight, too. My day's did about a week ago. His UMC actually stopped charging and showed a red light, fortunately I just happened to touch mine tonigh and found it to be too warm to touch for more than a moment.

I got made fun of on another thread for buying a second UMC as a back-up. I gotta say, I'm feeling a little smug at the moment. :wink:

image.jpg

image.jpg
 

Lightning Jeff

S 90D | 3 LR
Dec 22, 2009
57
0
Duvall, WA
Similar, perhaps minor, melting issues on my (faceplate-less) mobile connector:

image-1.jpeg
image-2.jpeg
image.jpeg


When I first got it, I was getting temperature readings closer to 100 - which also seemed somewhat high, but it's much hotter now.

I'll be stopping by Seattle SC this afternoon.
 

Lightning Jeff

S 90D | 3 LR
Dec 22, 2009
57
0
Duvall, WA
In my case, hard to say. It had been charging for perhaps a couple of hours last night when I thought to check it after seeing this thread. But I haven't had the 14-50 adapter off of the connector since I took delivery back in February. My guess is that the melting has been an ongoing process, rather than an instantaneous event.
 

Dave EV

Active Member
Jun 23, 2009
1,674
1,067
San Diego
Looks like there might be some sort of pin alignment issue contributing to the issue?

Too bad the pins on the adapters aren't as tough as the ones on the car.

144F is HOT especially considering that you're measuring the outside of the connector - the pins must be at least 20-30F hotter.

Personally I wouldn't charge at more than 20-30A or so until Tesla figures this one out and periodically check temperatures after 30 minutes of charging.

The real issue is that if you're using a timer, you might never notice the plug overheating until it melts, especially if you leave your UMC plugged in to the wall.

Is everyone who's had an adapter melt letting the "brick" hang from the plug as Lightning Jeff is in his pic? That puts a lot of strain on the connector - you can see that Lightning Jeff's adapter doesn't appear to be fully seated.

In the pics on this thread I also notice that the bottom of the power pins is the primary melt point - this reinforces the above theory that there is too much strain on the adapter.
 

Lightning Jeff

S 90D | 3 LR
Dec 22, 2009
57
0
Duvall, WA
Too bad the pins on the adapters aren't as tough as the ones on the car.
It's actually the connector pins, so if this is a flaw, it may be a more expensive one to fix. And yes, they seem tiny for the amount of current they're moving.

Is everyone who's had an adapter melt letting the "brick" hang from the plug as Lightning Jeff is in his pic? That puts a lot of strain on the connector - you can see that Lightning Jeff's adapter doesn't appear to be fully seated.
I'll be interested in what others do, as this always seemed a little off to me - to the point that I've thought about mounting a bracket for the "brick" to sit in and relieve that strain. That said, I actually don't think the strain is that great. I'm not sure that gap you see really is one - or that, given how tight the two pieces fit together, it contributes to any actual misalignment of the pins. But, you may be onto something.
 

Lightning Jeff

S 90D | 3 LR
Dec 22, 2009
57
0
Duvall, WA
The Seattle SC very quickly replaced my UMC. Happy to say, I now have a faceplate.

image-2.jpeg


The new one gets warm, but not the 140+ I saw with the old one. This is after about 90 minutes charging at 39 of 40 amps:

image.jpeg


I am still worried about the size of those pins, though - they seem awfully small.
 

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,697
I recently opened one of the UMC's up, but it's a pretty destructive process due to the housing overmold and it being glued shut. It's a "one-way" trip, so definitely do NOT try this at home!

?tesla-umc.jpg


?tesla-umc2.jpg


Tesla is really pushing the limits on the UMC design! When used with a 50A adapter, It's putting out a 66.7% Duty cycle, which equates to 40A. They use paired 2.5mm wires for each side of the line, (Equivalent to ~#13AWG) and inside the box they use the same P&B relay ClipperCreek uses on the LCS-25, a single 30A rated relay. (at 40A!) Now since it's almost never going to be expected to interrupt any sizable current, this is probably fine as long as the contact system in the relay is low enough resistance and there isn't too much heat dissipated. I haven't done any thermography yet.

It's arguable that splitting the high-current between 2 smaller conductors is better for heat-dissipation, but then you sometimes have pesky termination issues. Inside the UMC, Tesla welds the 2 conductors to a little square terminal, then screws this to a PCB terminal. So this is a good termination and it looked well-done by my assessment. Having 4 smaller wires instead of 2 larger ones definitely makes for a smaller, more flexible cable overall, so regardless of any potential current handling gain, it's good ergonomically.

I definitely don't like their interchangeable right-angle plug connector design. First off, if you are going to do right-angle, why not make it symmetrical? That way you could flip it 180 degrees if your outlet is installed upside-down. (Patent-Pending! =)

Their "dongle" design makes for elegant and simple plug adapters, but it ends up being a really big blob, especially when used on smaller outlets (NEMA 5-15). This will put even more stress on the outlet, with the high bending moment due to hanging the weight of the UMC and cabling off a long adapter conflagration. I think I prefer having a short length of cable for each adapter, as this makes the final plug smaller, more compact, more flexible, and spreads out heat. This is the design choice I made on the EVSE upgrade. I use a NEMA L6-20 (L6-30 on higher-power units) as my intermediary adapter connector, which is a good design, positively locks, and still very compact. Then I use a short cable to connect the adapters to the plug, and all connections are welded and fully overmolded. This maintains flexibility, reduces physical stress on the outlets, and spreads out any heat generated. It also means you don't need an adapter at all to "go native". I decided against right-angle choices on most adapters because there is no standard for outlet installation in the wild, and you could very often end up with a 180 degree wire exit, which is not a good idea.

-Phil
 

waidy

Member
May 6, 2012
257
2
Los Altos Hills, CA
I just use the UMC with the newly improved 14-50 adapter that was freshly evolved by Ingineer. It is now 2 hours into charging at 40Amp 240V, my Cen-Tech Infrared Thermometer gun reads 89.6 degree F at 14-50, and 121.4 degree F on the UMC body.
 

Doug_G

Lead Moderator
Apr 2, 2010
17,880
3,346
Ottawa, Canada
The contacts on the T92S7D12-24 relay has "Rated current" of 30A, but if you look at it in more detail they have a "limiting continuous current" of 40A.

The datasheet specifies how many operation cycles you can do at what current. At 40A/277VAC they are rated for 6000 cycles. Mind you, it is likely that Tesla is only operating the relay with the power off, since the car has much larger contactors. (Except they probably pull power immediately if a ground fault is detected - but you can do that 6000 times.)

So it does look like they are respecting the limits of the part... but yes, this isn't a conservative design!
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
My pins reached over 200 degrees after the UMC adapter melted. Tesla replaced, it's working cool again.
 

Neech

Member
Jan 24, 2013
172
8
Chicagoland
Did anyone notice if the power cable felt hot before the plugs melted? I noticed yesterday that my cable was very warm. Also, the unit with the green lights that show if it is charging properly is on backwards (it faces the wall when it's hanging). Now I'm a little worried it might not be wired properly. I'm going to get a bracket to put that unit on so it is not just hanging and I can keep an eye on the lights.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
Did anyone notice if the power cable felt hot before the plugs melted? I noticed yesterday that my cable was very warm. Also, the unit with the green lights that show if it is charging properly is on backwards (it faces the wall when it's hanging). Now I'm a little worried it might not be wired properly. I'm going to get a bracket to put that unit on so it is not just hanging and I can keep an eye on the lights.

Yes, it does, because the heat is carried through the wires, but there will clearly be a hot spot. In my case it was the connection between the UMC adapter head and the adapter itself. In one case on this forum, it's clear that it was a faulty receptacle rather than the adapter because the hot spot was at the 14-50 blades.
 

PhilBa

Active Member
Apr 20, 2013
1,382
68
Seattle
My new garage is getting wired right now so I am keenly interested in this topic. Several things to consider:


  • With that much current, contact area is a key issue. I'm pretty sure the spec assumes full contact along the entire pin/receptical. Any less contact area means higher current per unit of contact area and thus higher heat.
  • It looks like all the heat problems occur with the 14-50 connectors and not the screw terminals on the 14-50. Given that the early UMCs are getting replaced by Tesla, that says they are assuming insufficient contact area.
  • 14-50s in general weren't designed for a lot of insert/remove cycles. How many times would a dryer be plugged/unplugged? Care in inserting and removing is important. Try to be perfectly straight. It looks like the lower pins are where the problems occur. The right angle plug probably encourages putting upward torque on the plug when removing it, thus causing wear on the lower pins.
  • Dialing down the current mitigates the problem because it drops the amount of current flowing through the diminished contact area thus reducing the heat.
  • Making sure the 14-50 is very securely installed is important. No flex. Metal boxes (no plastic), securely mounted to a stud, everything really tightened down. A good electrician should do this but they sometimes cut corners.
  • Make sure that your UMC doesn't place stress on the outlet. Over time, movement could cause wear and reduce the contact area.
  • Something I don't know but will ask my electrician (who seems pretty good) - are there different grades of 14-50s? I see ads for industrial grade 14-50s. This is one area I won't skimp on.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
[*]Something I don't know but will ask my electrician (who seems pretty good) - are there different grades of 14-50s? I see ads for industrial grade 14-50s. This is one area I won't skimp on.

Different manufacturers test for different cycles. There isn't a standard, per se, for industrial vs. recreational grade, etc., but some may be built to be tougher (for example, 14-50's are used for RV's, so RV parks will experience a good number of cycles).

Most of the failures we're seeing are not related to the 14-50 blades, but rather the pin surface area between the adapter and the UMC's plug-head.
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Mar 8, 2012
19,580
22,043
Texas
14-50s in general weren't designed for a lot of insert/remove cycles. How many times would a dryer be plugged/unplugged?


A 14-50 is an RV plug, not a dryer plug (dryers use 30 amp circuits, not 50 amp). RVs are plugged in frequently. (Not saying that you're incorrect about the 14-50 not being good for that many cycles though--that seems to be normal even though RV plugs tend to be unplugged frequently)
 

dave

Member
Sep 21, 2012
462
5
Greater Cincinnati
So I caught my car still charging when I left for work this morning. It had been charging for about 4.5 hours on my 14-50 outlet. The charging cable was quite warm, but the connector going into the outlet was HOT. I really can't guess what the temperature was, but I was only able to touch it for about 3 seconds before having to remove my finger due to the pain from the heat. Yeah, I know, not very scientific. Maybe I have a low pain tolerance! :)

In any case, is that level of heat normal? Are you all able to to comfortably touch your connector after a few hours of charging? I have to admit it made me quite nervous. I don't know how hot things need to get to catch fire, but I am not used to my electronics getting that hot, and I'm wondering if I'm too sensitive or if I potentially have a bad adapter too.

your thoughts?
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Mar 8, 2012
19,580
22,043
Texas
In any case, is that level of heat normal?

No.

Are you all able to to comfortably touch your connector after a few hours of charging?

Yes. I just had my UMC replaced today for being hot (Called service before it actually melted.) What I felt was:

Panel breaker slightly warm (normal)
14-50 receptacle cool (normal)
14-50 adapter warm (normal)
UMC adapter end hot
Cable between UMC adapter end and GFI hot
GFI hot
Cable between GFI and charge port connector cool (normal)
Charge port connector cool (normal)

This was after about thirty minutes charging at 33 amps. I suspect it would have melted had I not stopped charging to let it cool down (there were 31 miles of range left when charging started)
 

dave

Member
Sep 21, 2012
462
5
Greater Cincinnati
Thanks for the advice jerry33. I had service swap out my UMC, and it is now much cooler while charger. I can comfortably hold the adapter while charging, and it is only "warm". There was definitely something wrong before.
 

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