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Leave plugged in outside for a week?

Discussion in 'Model 3: Battery & Charging' started by centikel, Mar 8, 2019.

  1. centikel

    centikel New Member

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    I have a Model 3 and live in Massachusetts. It’s cold out, sometimes rainy or snowy still. I’m going away next week for a week. I’ve just been using a nearby supercharger, though once I used an extension cord to my house 120v outlet just to see how it worked (it did).
    So, should I leave my car plugged into the 120v or leave it unplugged?

    I plan on getting a 240v outlet outside in he spring. I know an extension cord isn’t good.

    Thanks for any help!
     
  2. Rockster

    Rockster Active Member

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    Leave your car plugged in whenever you can. Period.

    If you're going to be gone a while, set the charge percentage to 50% or 60%.
     
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  3. jjrandorin

    jjrandorin Another BMW convert

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    If its only a week, and at home, and you are worried about damage to the cord or something, 1 week would be fine to leave it outside. Just charge it up to 90% before you go. People leave their cars at the airport with no charging, etc. If it was in a garage, I would say plug it in. Since its outside and you would be running an extension cord to it or something, I would say a week is fine. 2 weeks I would plug it in.
     
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  4. Needsdecaf

    Needsdecaf Member

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    Plug it in.
     
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  5. halfricanguy

    halfricanguy Model 3 - LR RWD - MSM

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    Typically I would suggest leave it plugged in. However, the long-term use of an extension cord without supervision and being outdoors would worry me, so I would personally charge it to 80% or so then leave it unplugged, unless your confident with the weather proofing and durability of the extension cord.
     
  6. antoinearnau

    antoinearnau Member

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    I would definetly leave it plugged in. Piece of mind.
     
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  7. Grassright

    Grassright Member

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    Not plugging in for only one week is perfectly fine. Just charge to 90% before you leave. Most likely you will still have > 60% when you are back.
     
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  8. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    I'd leave it plugged in. A plugged in Tesla is a happy Tesla.
     
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  9. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    Definitely plug it it. Make sure the connection between UMC and extension cord is covered and won’t gather water. Tape it if you need to.
     
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  10. Vines

    Vines Member

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    The only downside to leaving it plugged in and unsupervised is that the receptacle in the wall could overheat without any other fault. If I was going to leave it plugged in I'd want to make sure that this outlet is known to be good, and not a fire hazard. I'd prefer an outlet in a surface mounted metal box, vs just a plastic box flush mounted in some sheet rock.

    There is a temperature sensor in the mobile connector plug, but using it with an extension cord defeats this safety feature.

    I'd probably leave it unplugged if i wasn't totally sure about the outlet.
     
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  11. WileyTheMan

    WileyTheMan Peanut Gallery Member

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    Interesting. I knew charging with an extension cord was not recommended but I didn't realize it compromised safety functions of the charger. Had I known that, I would not have been charging like that for the past nine months. :)
     
  12. Big Earl

    Big Earl Supporting Member

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    Plan on the car consuming 1 - 2% per day while parked. If you have apps that poll the car for data periodically, it might use more.

    The car will be fine unplugged for a week as long as you don't have an app that's constantly polling it for information (like TeslaFi and others). If you charge it to 80% before you leave, it will probably be around 70% when you return.

    If you had a garage or a hard-wired charging station, I'd say go for it, plug it in. There's no reason to leave your UMC outside for a week while you're away, exposing it to the elements, vandalism and theft.
     
  13. Vines

    Vines Member

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    Its actually not an insignificant risk. I do know a customer who burned his garage severely doing this. He did not use a dedicated outlet, used an extension cord into his garage. Then the outlet heated up, significantly failed and started a fire in some debris in his garage and it was self sustaining from there. It just takes one bad remodel job or outlet failure.

    If you must do it, be extra sure of the outlet quality, and the wiring when you run an extension cord. Make it a really good heavy duty extension cord, 10AWG minimum. Know that every outlet on that circuit is a possible failure point, so only use dedicated circuits.
    If you are unsure of the quality of the outlet, you can always dial back the amps to 8A or so. I also advocate putting a hand on the outlet itself just after charging. Get used to what a normal temperature feels like after a few hours. Test every outlet you use like this at a minimum, and consider them a fire hazard until proven otherwise. If an outlet ever feels too warm, replace it immediately.
     
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  14. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    Sounds like rubbish to me.
    How would the UMC know whether it's plugged into the socket on the end of an extension cord, compared to a wall socket?
     
  15. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    If the socket is built to code then it can take the load no problem.
    If it's not built to code then having a metal box won't help, the overheating could occur anywhere in the walls between your meter box and the outlet.
     
  16. Vines

    Vines Member

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    It has a temperature sensor in the plug end of the UMC. If this plug detects overheating, it will stop the charging. Therefore the UMC will sense the temperature of whatever its plugged into. If the outlet or extension cord is overheating it will stop the car charging.

    Your position does not recognize a couple things:
    1. Resistance increases with number and quality of connections. The more outlets ganged together on a single circuit, the more times power transitions through the outlet, increasing points of failure. While it may be code to gang several outlets together, its not the best plan for a dedicated EV plug.
    2. A dedicated wire run in EMT with no other outlets except the EV dedicated circuit, and the high quality outlet in a metal box is the safest installation possible. A plastic box with any grade outlet ganged to several other outlets may be code.
    3. NEC code recognizes this need for increased safety and treats EV dedicated charging circuits differently than other household plug in circuits.
    4. While possible to have a break in the wiring anywhere, its most likely to happen at a junction box, outlet or other field made connection.
     
    • Informative x 1
  17. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Not rubbish at all. The UMC also senses the resistance. A really heavy duty extension cord will have similar resistance to wall wiring. A thin extension cord will have more resistance. The UMC will turn red and refuse to charge if the resistance is too high.
     
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  18. Dana1

    Dana1 Supporting Member

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    Plugged in Tesla is a happy Tesla. That being said, lol, I don’t charge every night. If you use an extension cord don’t be cheap. Use a heavy duty extension cord, as short as possible. Some Ridgid models have an integrated fuse.
     
  19. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    That’s what I’m saying.
    The UMC will provide the same overheat protection whether its in an extension cord or.not, so its “rubbish” to say that using an extension cord bypasses this safety mechanism.
    The UMC sees no difference between dodgy sub-code house wiring, and a dodgy extension cord. Both cause a temp rise, which increases wire resistance, which triggers the UMC shutdown.
     
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  20. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    The simple point is that the UMC detects insufficiency circuit gauge by detecting an increase in resistance, which will spike as heat increases.
    An extension cord simply adds length to the existing wiring. It its gauge is sufficient then it’s no problem. If it’s gauge is not sufficient then the UMC will act exactly the same as if it were plugged into sub-code household wiring.
    On other words, it’s “rubbish” to say that an extension cord bypasses the UMC shut-off mechanism, which was the content of my post.
     
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