TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

Home charging on a 35A circuit...

Discussion in 'Model 3: Battery & Charging' started by marshpaw, Dec 28, 2019.

  1. marshpaw

    marshpaw Member

    Joined:
    Dec 5, 2019
    Messages:
    15
    Location:
    Bay Area, CA
    I just took delivery of my M3 LR AWD and I'm trying to figure out my home charging situation. I live in a recently built house which came with a 220V circuit wired in the garage but with no receptacle installed. So I figured I could use the Mobile Connector and buy the appropriate NEMA adapter and receptacle. Checking my panel, I realized the circuit is connected to a 35A breaker which I quickly realized is not very common, or at least doesn't easily fit into any of the adapter categories.

    I'm at a bit of a loss of what to do, but I figured I would go the 30A route and get a NEMA 14-30 adapter and install the appropriate receptacle. I'm not an electrician by any means, but in my train of thought it seems safe since I'm using the adapter that the car knows to only draw 24A and I'm using a receptacle that is rated for 30A. I'm wondering if there is any other potential risks I'm not seeing...

    Has anyone else run into this dilemma while trying to setup charging at home?
     
  2. RFernatt

    RFernatt Solar/EV Owner/Enthusiast

    Joined:
    Oct 13, 2016
    Messages:
    645
    Location:
    Eastern Panhandle, West Virginia
    If everything (receptacle, wiring, breaker) is rated for at least 30A and you'll only be drawing a 24A continuous load, you should be good as long as it is wired up properly.

    35A is odd. Wiring support more by chance? If it did and you had capacity, you could bump up the breaker and receptacle.

    Of course, you should probably also consult an electrician to be sure.
     
    • Like x 1
  3. harveyd396

    harveyd396 New Member

    Joined:
    Dec 28, 2019
    Messages:
    1
    Location:
    Miami, Florida
    Hi, This is what I did, similar setup at home. My house has a 150 amp entry, I installed a 60 amp set of breakers in the panel and installed a NEMA 1450 female flush mounted receptacle. This gives me 32 amps to charge my new model 3P. But since I can regulate the charging amps from 1 to 32 amps, what is the optimal charge rate for battery health? I have unlimited time to charge the battery, so I don't need to charge at the full 32 amp rate. I'm trying to learn what it the best rate of charge to bring the battery to 100% charge without harming it.
     
    • Disagree x 1
  4. RFernatt

    RFernatt Solar/EV Owner/Enthusiast

    Joined:
    Oct 13, 2016
    Messages:
    645
    Location:
    Eastern Panhandle, West Virginia
    Well, for battery health, you don't want the battery sitting at a high level of charge. The car will warn you if you charge at 90% or greater repeatedly. I set mine at 80% and only increase if needed on a trip.

    Regarding the speed of charge, I don't know that I'd be concerned. A Model 3 charging at a V3 Supercharger would be dealing with more than 30X the power. There could be some argument on whether it is better to charge faster and finish sooner vs charging slower and letting the car be in a charging state for longer, but with the relatively small amount of energy in use, the difference is likely negligible. I will bump the amps down a bit on my EVSE if I'm charging to a high percentage and want the charging to finish closer to my departure time so that the battery is warm, but generally I feel that it's better to finish charging sooner so that auxillary systems (cooling, BMS, etc.) are running the least amount of time.
     
  5. I<3URANUS

    I<3URANUS Member

    Joined:
    Dec 9, 2019
    Messages:
    122
    Location:
    Dallas
    I went with a wall connector.

    Was a simple run under my main panel. 6-3 run.

    Works like a charm.
     
    • Like x 1
  6. I<3URANUS

    I<3URANUS Member

    Joined:
    Dec 9, 2019
    Messages:
    122
    Location:
    Dallas
    #6 I<3URANUS, Dec 28, 2019
    Last edited: Dec 28, 2019
    You're really overthinking it. 32amps is fine at 240v. No need to worry at all.
     
    • Like x 3
  7. ucmndd

    ucmndd Well-Known Member

    Joined:
    Mar 10, 2016
    Messages:
    5,923
    Location:
    California
    The car does NOT warn you if you charge to 90% repeatedly. There's nothing wrong with charging to 90% regularly, and in fact people have posted service notes from Tesla recently recommending exacly that.
     
    • Like x 3
  8. I<3URANUS

    I<3URANUS Member

    Joined:
    Dec 9, 2019
    Messages:
    122
    Location:
    Dallas
    This. I charge to 90% daily. There's literally no reason not to. Simple as that. This charging debate is kinda out of hand. Just drive it. Charge it to what you feel comfortable for. That's really all anyone needs to do.

    Even if you charge to 100% occasionally is no biggie. Hell, so long as it doesn't sit for months and months at full charge you won't damage the battery.

    Just drive it.
     
    • Like x 1
  9. RFernatt

    RFernatt Solar/EV Owner/Enthusiast

    Joined:
    Oct 13, 2016
    Messages:
    645
    Location:
    Eastern Panhandle, West Virginia
    #9 RFernatt, Dec 28, 2019
    Last edited: Dec 28, 2019
    Uh, my car warned me specifically about charging to 90% after a couple times, so at least my LR Model 3 built in Sep 2018 did in fact display a warning not too long ago. Maybe it has changed, but there you have it. I believe what the car displayed on its screen more than someone on the internet, but do what you like.

    I do agree that most charging discussions are overthinking it, especially L2 charging.
     
  10. iluvmacs

    iluvmacs Member

    Joined:
    Jan 27, 2014
    Messages:
    473
    Location:
    Madison, WI
    60A breaker on a 14-50 outlet violates code. Needs to be 50A.
     
    • Like x 4
    • Informative x 1
  11. iluvmacs

    iluvmacs Member

    Joined:
    Jan 27, 2014
    Messages:
    473
    Location:
    Madison, WI
    #11 iluvmacs, Dec 28, 2019
    Last edited: Dec 28, 2019
    Definitely the easy/safe choice. Technically, per code, you could “round up” to a 50A outlet, but you would have to make sure you limit the car to 28A (80% of 35A). The extra 4A isn’t worth the hassle, so just go with a 30A setup. Though, you will need to change the breaker to 30A.
     
  12. ZOMGVTEK

    ZOMGVTEK Member

    Joined:
    May 19, 2015
    Messages:
    558
    Location:
    'Merica
    Install a 30A receptacle and replace the breaker with a 30A one. That nets you quite reasonable charge speeds, no worries. A 35A double pole breaker is a bit of an oddball. Maybe the guy had it in the truck or something and wanted it gone.
     
    • Funny x 1
  13. eprosenx

    eprosenx Active Member

    Joined:
    May 30, 2018
    Messages:
    2,062
    Location:
    Beaverton, OR
    We need to figure out what kind of wire is installed to give proper advice. A 35a breaker is a bit odd. This makes me think it might have been for an AC unit and AC units can be breakered higher than the ampacity of the wire in some cases.

    So we need to know what wire gauge it is, whether it is copper or aluminum (likely copper), how many conductors there are, whether it is NM cable (romex) or something else.

    Most likely it is 10 awg copper Romex (or even #8), and hopefully it has two hots, a neutral, and a ground. If it is #10 as described, then I would do a NEMA 14-30, swap to a 30a breaker, get the 14-30 adapter and call it a day! If you are lucky enough to have #8 awg then you could do a 6-50 or 14-50 on a 40a breaker and charge at 8 amps. I would not install that in a new install since it is best to have a 50a circuit on those two receptacle types, but if you have the wire in the wall this is fully code legal and I would have no issues doing it (I might label this on the receptacle as a 40a circuit).

    If you are unlucky and you have #10 awg copper and only two hots and a ground, then things get a little more difficult. There are solutions, but no obvious slam dunk.

    Feel free to post pictures of the wire and breaker panel and stuff (inside too if you can safely remove it) and we can provide advice. Sometimes running a new line is easier in general.

    Good luck!
     
  14. eevee-fan

    eevee-fan Active Member

    Joined:
    Dec 2, 2019
    Messages:
    1,149
    Location:
    Nevada
    My neighbor drives his Model S to/from his office 2 miles away. I convinced him to crank it all the way down. He has it set to 5A with a wall charger. On another post, owner mentioned running his at 40A and seeing burn marks on NEMA 14-50 receptacle and smelling slow burn. Best advice is to set it to the lowest amp based on the range you need. The lower the better. On another post, owner is having problem of the charger connecting properly and the car limits charging to 16A instead of 32A. So 16A seems to be Tesla's recommended highest safe charging rate.
     
    • Disagree x 6
  15. ucmndd

    ucmndd Well-Known Member

    Joined:
    Mar 10, 2016
    Messages:
    5,923
    Location:
    California
    Tesla software, in any of their vehicles, has never issued any warning when charging to 90% repeatedly. I’ve done so approximately 1,000 times in the last 3 years.

    You must have had your slider set higher than 90%.
     
    • Like x 2
  16. RFernatt

    RFernatt Solar/EV Owner/Enthusiast

    Joined:
    Oct 13, 2016
    Messages:
    645
    Location:
    Eastern Panhandle, West Virginia
    It's possible since the slider wasn't very precise in previous app versions even though I was aiming at the 90% mark. Could have been 91% I suppose. But warning you at 91% and not 90% doesn't give me warm fuzzies and the car can sit without driving for days at times, so I err on lower is better for me.
     
    • Like x 3
  17. eevee-fan

    eevee-fan Active Member

    Joined:
    Dec 2, 2019
    Messages:
    1,149
    Location:
    Nevada
    General advice on Li-ion battery is to keep it between 20-80%.
     
  18. eprosenx

    eprosenx Active Member

    Joined:
    May 30, 2018
    Messages:
    2,062
    Location:
    Beaverton, OR
    Hrm, I disagree with this. Properly installed receptacles/circuits should be perfectly safe up to their rated capacity. The issues with melted receptacles are all with bad installs coupled with low quality receptacles. I charge my M3 L3 at the full 48 amps every single day with zero issues.

    Turning your charge rate all the way down to five amps will run your cooling pumps and computers a lot more than is necessary. I could see some argument for turning down a bit perhaps to stress things less, but 5 amps is crazy.

    The issue in the other thread surrounding 16 amps is purely around the marching mechanism failing to work. Without it latched it is an arc flash hazard if you unplug it under load. The car detects this and limited the charge current. With a working charge latch I would have zero issues running at full charge speeds.

    Any level 2 charging is so much hilariously slower than a supercharger that it does not stress the battery at all. The only thing it could stress is the rectifiers and the site wiring for the EVSE.
     
    • Like x 3
  19. eevee-fan

    eevee-fan Active Member

    Joined:
    Dec 2, 2019
    Messages:
    1,149
    Location:
    Nevada
    If you believe there's any cooling needed when charging the EV battery at 5A or the rectifier running at 5/40 of its capacity reduces useful life, I guess then your argument would make sense. It's like saying zooming from stop light to stop light then slamming on the brakes is better for your car vs accelerating slowly and letting it regen to a stop. :)

    Lower amp, longer draw, benefits both the electronics in the EV and the power company would appreciate it too.
     
    • Disagree x 5
  20. eprosenx

    eprosenx Active Member

    Joined:
    May 30, 2018
    Messages:
    2,062
    Location:
    Beaverton, OR
    I think it runs the cooling pump any time any charging is underway. So yeah, generally I agree that lower charge rates are good, but I think there are limits to it. The pump having to run longer is my main concern.
     
    • Like x 1

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC