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tliving
Member
I have 2 UMCs, one in the car at all times and one plugged in since April 2014...
The UMCs tend to die about every 12 months (each of them) and so far the SC has just given me a new one. The problem is unrelated to the NEMC 14-50 side but they haven't told me why they die so fast. I've had 3 replacements so far.
The UMCs tend to die about every 12 months (each of them) and so far the SC has just given me a new one. The problem is unrelated to the NEMC 14-50 side but they haven't told me why they die so fast. I've had 3 replacements so far.
thecloud
As rhythm raced inside, the ship came alive
It's (probably) because you are charging at 40 amps, so they get too hot. Try dialing it back to 32 amps.
My original UMC has had no issues in 2 years of use.
tliving
Member
Tesla hasn't suggested that and they're supposed to be rated to handle the 40A. The problem manifests itself as unable to get a good connection when plugging into the Tesla. Generally it works fine for about a year then it just starts getting really hard to get it connected.
Yep, pretty sure that's exactly it. I've been using about 31 or 32 amps on mine, which came in March 2014, so that's about 2 and a half years old.
Uh, sure, and a car's speedometer goes all the way up to XXX mph, and some structure is rated to support up to a certain amount of weight, and that paper shredder can handle up to XX sheets at a time, and something is supposed to withstand up to a certain temperature, etc. etc. Running ANYTHING at its maximum rated level all of the time usually stresses it and shortens its life. This is a basic mechanical/electronics principle and is not Tesla-specific.
Let me add one more aspect to this. This is not just about when it is running at 40A. It's about temperature cycling. When it is not being used, all of the electronics are sitting at room temperature. When you use it, you heat it up some. Then when you stop, it cools back down to room temperature. This happens every. single. day. So the question is: How far of a differeential up from room temperature do you want to heat those components? How far that temperature moves away from room temp is the thermal stress on all of the components and solder joints. If you can heat it up just a little and then back down, that is much less stress.
Mine has been plugged in like this for 3.5 years, no problemI just picked up my new MS yesterday and had the same question. Thank you all for reassuring me that it is ok to leave the UMC plugged into the NEMA 14-50.
Is there any way to rest the large and heavy (transformer?) unit with the Tesla logo and green light so it doesn't put continuous strain on the plug and receptacle? I have ordered the Tesla cable organizer. Here is a pic of what I am referring to...I would love to see any pics of similar setups.
Thanks in advance!
tliving
Member
Thats a terrible analogy. The car and UMC come preconfigured to charge at that speed and the manufacturer doesn't recommend you change it in ANY writing, blog posts, etc. There's a reason the 50A outlet (NEMA 14-50) is derated to 40A and that Tesla's instructions are clear that your outlet needs to be able to sustain 40A charge rates for long periods.
I use and older version of this bracket: Organize your UMC: Wall Bracket for Charging Cable Controller
thecloud
As rhythm raced inside, the ship came alive
Well, the fact remains that you have gone through 3 replacements, while most of us have had 0 replacements. So what do you think the difference might be? I suggested one possible difference, which is that I keep mine limited to 32 amps to avoid heat issues. I also don't charge on a daily basis, so frequency of plugging and unplugging might be another difference.
You mentioned that the problem "manifests itself as unable to get a good connection when plugging into the Tesla." I wonder if the problem is dirty or corroded contacts in the UMC's charge handle over time. Do you use it outdoors a lot?
It’s not a terrible analogy; it’s science. There are electronics and circuit boards in there that get hot if you run it at its maximum level, and then it gets cold, and then it gets hot, etc. etc. Those large temperature swings stress the components and solder connections and create metal fatigue and shorten their lives. You can get upset and complain about these facts, or you can do something to alleviate them.
No, of course they don’t recommend that. They don’t want to have egg on their face by admitting that they underdesigned the UMC and HPWC. They both run hot at their maximum current. But do you shake your fist and curse at the sky when it rains on you, or do you do something to keep from getting wet?
Well yeah, there is a reason for that, but that is related to the electric code for the wall wiring and outlet, which can handle the 40A just fine. It’s the UMC that has a problem. That is how the U.S. decided to do their wiring standards for short term versus long term loads. They decided that they would spec the wire size for temporary loads, but it would have to be derated for constant loads. In most of the European countries they didn’t do it that way. If there is a 50A circuit, it is built with thicker wire that is OK with a 50A constant load 24/7.
Granted, maybe more people should be suggesting to Tesla that they beef up the wire and connections in these devices so they have more margin to not heat up and degrade as much at max level, but it’s ridiculous for you to argue with us that it’s not happening when we explain to you what is going on.
alexvirital
Member
Hey, question for folks who leave theirs plugged in - any recommendations for doing so outdoors? (Aside from "Get an HPWC", i'm working on it!) I'm concerned about doing so in the winter if we get any decent snow this year.
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