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My new UMC is room temperature. My failing one got way too hot to the touch. My guess is that your UMC is on its way to melt-ville.
Charged_Up
Member
Warm is ok; very hot should be checked. I have had a couple of mobile connectors that needed replacement, one because it was hot to the touch - all during 40 amp charging. Better safe than sorry....
Duckjybe
Member
I had an issue with my 14-50 adapter getting very hot to the touch. After I replaced the whole UMC it was cool to touch. But if I slide my hand down the cable from the 14-50 to the head unit it gets progressively warmer. If I then slide my hand from the other side of the head unit toward the car it gets progressively cooler. This suggests the heat is coming from the head unit electronics which I think is normal.
I decided to check the temp on my UMC and 14-50 adapter. Charging at 40 amps with about 75 miles range available. It was pretty hot so I went and got my laser temp gun to see just how hot it was. First off this is in Florida and it was about 73 degrees. The hottest part was at the 90 degree bend were the cable starts from the charge adapter end of the UMC (14-50 end) it was 175 degrees there. The cable below was about 135. Box on UMC was 105 closer to the car the cable was also about 105. That seems ok but the portion that plugs into the outlet seems to be to hot possibly.
I lowered the amps to 25 for the rest of the night.
Just wondering if anyone else has measured?
Outlet is outside adjacent to my main entrance panel.
I lowered the amps to 25 for the rest of the night.
Just wondering if anyone else has measured?
Outlet is outside adjacent to my main entrance panel.
175 deg is far too hot. I am guessing your adapter will show some signs of pin melting. Call the svc center.
UberEV1
Member
@BlkCld - Curious whether you still have the high temperatures and temperature differences in your UMC cables. Have you discussed with the SC experts? Just trying to understand normal vs. abnormal. Thx!
UberEV1
Member
@spaghetti - thank you for the additional data! That would mean that BlkCld's results are indeed much too hot. I'll measure my temps as well and report in a week or so.
ClearwaterBchSteve
P445 / VIN 1794
I have a home-made adaptor to mate my UMC 14-50 to an "old-school" 50A 3 prong 10-50. Even though the wall jack is fused and rated at 50A, I've always set the maximum current to 35A for a safety factor since the adaptor I built is far from 'certified". With a laser thermometer, I've measured temperatures on the back side of the UMC connector (the part attached to the cable) in excess of 160deg F. After installing the replacement 14-50 adaptor from Tesla, the Model S has detected a "fault" and reduced the current draw to 30A. This was in Florida with a 85 degree ambient temp, but still plenty of voltage available (240v). The high temperatures were on the Tesla cable side (not my adaptor, wall jack or receptacle)
I'm pretty confident that a continuous 40A draw on a standard UMC is at the thermal limits - hence Tesla's reasoning for issuing "smarter" adaptors that can instruct the car to reduce current draw as temperatures rise.
I'm pretty confident that a continuous 40A draw on a standard UMC is at the thermal limits - hence Tesla's reasoning for issuing "smarter" adaptors that can instruct the car to reduce current draw as temperatures rise.
UberEV1
Member
Just picked up my car today from the Service Center - another very positive experience (Go Tesla!). I had scheduled the appointment a while back for tire rotation and other checks, but when I shared my cable temperature data (see below), the Service Manager asked me to bring in my UMC cable to be checked as well. The conclusion was that the cable was indeed running hotter than normal under their controlled test conditions and thus they replaced it at no charge. Here are some quick takeaways for the community . . .
* The SCs appreciate detailed data, but must doublecheck themselves to confirm issues (understandable)
* There isn't a specific temperature limit or threshold above which the cable is known bad. Reason is that we all charge our cars under different environmental conditions (e.g. ambient temp, sun/no sun, nearby appliances, etc.) and thus there is some reluctance to set one guideline
* Nonetheless, with a check at the SC, and cross-check to a known-good cable under the same exact conditions, they can quickly etermine if the cable is good or bad
* General Guidance (mentioned as well by other posts): If the cable is warm, that is normal; if the cable is hot such that you cannot hold it in your bare hand for any length of time, then it should be checked.
When I have more time, I'll measure the temps on the new UMC cable for comparison. In the meantime, for those who like data, this is for you . . .
bancroftc
Member
Bumping this thread as I'm having some heat concerns with my UMC. I'm not sure what level of heat is normal. I have a NEMA 14-50, professionally installed by Tesla recommended vendor. 50A circuit and I get 40A draw, 239-240V and 30mi/hr charging. So from that standpoint it's charging perfectly.
Last night I just went out to check on it. Started charging at about 70% SOC with limit set to 90%. When I checked on it, it had been charging for maybe an hour and a half, near the end of the charging cycle and I was getting the above charging metrics as I usually do.
Side note, I have my adapter plugged into the wall with the brick hanging down below that. From there, the main length of cord is coiled around a Tesla wall cable organizer. My charge port is pretty close to this setup, so I don't need to unwind much to plug in, therefore most of the cable is coiled up on the organizer.
Plug adapter was warm, nothing alarming. The Tesla "brick" and the short cable to the adapter was warm, nothing alarming. Main length of cable hanging on wall organizer was HOT. I did a rudimentary test with an instant read meat thermometer in between the coils of cable on the organizer and read just under 130 degrees F. I would suspect the actual temperature is probably a bit higher based on how I measured it (need to bust out my FLIR One). This was somewhat alarming and is the reason for my question here. The cables are not tightly coiled FWIW. Similar to how Tesla shows it on their website, if not looser.
The remaining length of cord and the connector to the vehicle were only slightly warm.
Is it normal for the cable to heat up to that extent? Tonight I'll uncoil it to see if that helps dissipate some of the heat.
Anything to be worried about?
Last night I just went out to check on it. Started charging at about 70% SOC with limit set to 90%. When I checked on it, it had been charging for maybe an hour and a half, near the end of the charging cycle and I was getting the above charging metrics as I usually do.
Side note, I have my adapter plugged into the wall with the brick hanging down below that. From there, the main length of cord is coiled around a Tesla wall cable organizer. My charge port is pretty close to this setup, so I don't need to unwind much to plug in, therefore most of the cable is coiled up on the organizer.
Plug adapter was warm, nothing alarming. The Tesla "brick" and the short cable to the adapter was warm, nothing alarming. Main length of cable hanging on wall organizer was HOT. I did a rudimentary test with an instant read meat thermometer in between the coils of cable on the organizer and read just under 130 degrees F. I would suspect the actual temperature is probably a bit higher based on how I measured it (need to bust out my FLIR One). This was somewhat alarming and is the reason for my question here. The cables are not tightly coiled FWIW. Similar to how Tesla shows it on their website, if not looser.
The remaining length of cord and the connector to the vehicle were only slightly warm.
Is it normal for the cable to heat up to that extent? Tonight I'll uncoil it to see if that helps dissipate some of the heat.
Anything to be worried about?
At first I thought you may have a broken wire in the cord, since the UMC uses two parallel wires for each conductor. However, in that case I would expect to find that the entire length of the 18' cord between UMC unit and car would be the same temperature as the current would be using the entire cord.
It's difficult to say without more testing. I would uncoil the cord and do some more measurements along it to determine where it gets hot, and that would give a better idea, as you noted.
Tesla says you should be concerned if it goes above 140 degrees F on the HPWC, but that's the standard related to the handle that plugs into the car (usually high resistance from the car-to-coupler pins).
It's difficult to say without more testing. I would uncoil the cord and do some more measurements along it to determine where it gets hot, and that would give a better idea, as you noted.
Tesla says you should be concerned if it goes above 140 degrees F on the HPWC, but that's the standard related to the handle that plugs into the car (usually high resistance from the car-to-coupler pins).
For typical overnight charging, I would not use the full 40 A capability, espically if it is running that hot. If you set the car at 32 A, you are stressing the system less and should be done charging by the time you are ready to leave in the morning.
I am curious about the temperature you get with the cable stretched out instead of coiled. I have noticed that my 100' 120 V extension cord seems to get hotter when it is loosely coiled up, instead of stretched out. The coils should increase inductance, and therefore increase AC impedance, but I don't know if the effect would be noticeable or not.
GSP
I am curious about the temperature you get with the cable stretched out instead of coiled. I have noticed that my 100' 120 V extension cord seems to get hotter when it is loosely coiled up, instead of stretched out. The coils should increase inductance, and therefore increase AC impedance, but I don't know if the effect would be noticeable or not.
GSP
bancroftc
Member
Thanks - I will try both dropping the amperage and uncoiling and report back! With my daily driving I'm back to 90% within a couple hours of being home so I can definitely go lower without issue.
Cottonwood
Roadster#433, Model S#S37
Reducing current will reduce power dissipated and therefore temperature. The power transferred is proportional to the current (I) and the power is proportional to the current squared (I[SUP]2[/SUP]). Therefore cutting current to 80% will reduce power to 64% and temperature rise accordingly. By the way, reducing current to 70% will approximately reduce power and temperature rise to half (actually 49%).
The cord getting hotter when it is coiled up, has nothing to do with increased inductance of the coil. It is just a thermal issue. A stretched out cord has much more area over which to dissipate the heat. A coiled up cord has less surface area and a higher thermal resistance. With the same power in and less area over which to dissipate the heat, the temperature of the wire rises until there is enough temperature to get rid of the heat (power).
After nearly 3 years I finally decided to upgrade my charging setup from a 14-50 outlet + UMC to an 80A circuit with the HPWC. There were three reasons for me to do this.
1. Ever since the 5.8.4 firmware download I've had unresolved charging issues with the car backing down to 30A.
2. I've always felt that the UMC should have been designed a little better for a continuous 40A load.
3. Tesla lowered the price of the HPWC (in 2014?) to $750.
Ever since I had the HPWC installed, I've had zero charging errors. The heftier cable on the HPWC barely warms up at all since it's only drawing 64A continuous and it was designed for 80A continuous. So I figure that with Tesla significantly reducing the price of the HPWC, that they either got a super deal from their supplier, or Tesla would really rather a majority of their customers use the HPWC instead of the free UMC, or both.
A side benefit is that I'm taking advantage of the dual chargers in my car, and at 64A I'm able to charge super fast at home. At that rate, I add 47 miles of range per hour, which is overkill for home charging, but it's nice to have on a small number of days when I do a lot of driving.
1. Ever since the 5.8.4 firmware download I've had unresolved charging issues with the car backing down to 30A.
2. I've always felt that the UMC should have been designed a little better for a continuous 40A load.
3. Tesla lowered the price of the HPWC (in 2014?) to $750.
Ever since I had the HPWC installed, I've had zero charging errors. The heftier cable on the HPWC barely warms up at all since it's only drawing 64A continuous and it was designed for 80A continuous. So I figure that with Tesla significantly reducing the price of the HPWC, that they either got a super deal from their supplier, or Tesla would really rather a majority of their customers use the HPWC instead of the free UMC, or both.
A side benefit is that I'm taking advantage of the dual chargers in my car, and at 64A I'm able to charge super fast at home. At that rate, I add 47 miles of range per hour, which is overkill for home charging, but it's nice to have on a small number of days when I do a lot of driving.
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UberEV1
Member
@bancroftc: In my data set, the coil of downstream cable was much cooler than the upstream portion between UMC and wall plug. I'm sure there are multiple ways the cable can go bad, but based on my own experience, I would be more concerned about the portion of cable between UMC and car heating up, as it may indicate the controller is not working properly to control power flow to the car. My recommendation would be to ask the Service Center to check the UMC for you.
Good luck!
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