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Home charging at 20 amps?

Discussion in 'Tech Talk' started by Ev43, Apr 5, 2017.

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  1. Ev43

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    #1 Ev43, Apr 5, 2017
    Last edited: Apr 6, 2017
    Hello All,

    It has been determined that I can install a 20 amp circuit in my garage that should, according to Tesla, achieve an 11 mile per hour charging rate. I don't drive a lot of miles so it sounds like this should be sufficient for my needs. [My home main electrical panel is close to maximium, necessitating the restriction to a 20 amp circuit.]. Do you folks think that I am kidding myself by going this route? I could upgrade my main electrical panel to 200 amps but it would cost upwards of $4000 and require the new panel be installed on the front of the house. This option is not very desirable from both a cost and cosmetic perspective.

    Any words of wisdom are welcome.

    Many thanks,

    Ev
     
  2. garsh

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    It's not ideal, but it could work for your specific situation.

    Right now, I own a Nissan Leaf. I've just been using the "trickle charger" that came with the car and plugs into a regular 120v outlet. IIRC, it draws 12 amps. For daily use, this is fine. I charge to full at work (L2 charger). I charge a little bit overnight just to have enough to make it to work the next day. Most importantly, I have a second vehicle.

    The problem is the abnormal circumstances. I drive home from work, and need to take one kid to school, and another to a friend's house. Then I need to pick them up again. The low-current charging means that I can't use my Leaf to do all of it.

    So, do you have a second car that you can use for these less-common scenarios? The larger range of the 3 also means that you won't often find yourself limited by battery capacity like I am. Do you have L2 charging or superchargers nearby just in case? You'll have to think about your worst-case scenarios to decide if you can live with this.
     
  3. BigBri

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    I'll be in a similar boat probably as I'm having a hard time getting approval to install a more powerful charger. I'd just make sure you have a local option to charge in a pinch but beyond that you're probably golden. I'm fortunate enough to have a supercharger 5 minutes away.
     
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    • Dan Detweiler

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      I have been driving a Volt for the last 4 years. I have charged on the normal 110 volt outlet the entire time. Having said that, I average about a 25 mile a day commute and I have a gas engine for backup for longer needs.

      Your situation may not be ideal but it is certainly doable, especially with a light daily use.

      Dan
       
    • AEDennis

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      Sounds like you own your home...

      If you install solar on your roof, your main will probably be upgraded to 200A as part of that process. So, the cost to install a 200A main and EV charger can be offset by the savings that you will garner from generating your own power.

      Plus, I normally charge at 30A per day and have a 56A HPWC installed that I use sporadically, for those days when I don't need to supercharge or need to charge quickly.
       
    • Rich Nuth

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      It really depends on how much you drive on a daily basis and the proximity to a faster charger (SuperCharger) when you need it. Consider this: at 11 miles per hour of charging it will take about 4.6 hours to add back 50 miles to your battery. If that is close to what you are driving today then you should have no problems. But if your life situation changes and you need to drive a longer distance to work (for example) you could find you need more current for charging than you allowed for.

      Just be prepared to increase the size of your electrical system in the future as your needs change.
       
    • Todd Harrison

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      An option you may consider would be buy a gas range or dryer and use the 40 or 50 amp circuit you free up for your car. Could also run a cord from the dryer to the garage, have to unplug the dryer every night? My panel is almost full but I have gas dryer and range, I will use one or the other.
       
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      • 18M3

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        #8 18M3, Apr 5, 2017
        Last edited: Apr 5, 2017
        I was faced with this same issue last year when I bought a 2013 Leaf to test out the whole EV-car thing. This car was intended as a test for me. After getting my Model 3 reservation, I wanted to be sure everything fit my lifestyle without big headaches and too much extra effort. I got an estimate for an electrical panel upgrade, but instead I did what Todd suggested and used a 40 amp circuit that was previously for a clothes dryer converted to gas. The electrician used the existing breaker and installed a new plug in my garage for less than $1000US. I charge every day at my office to cover a 28mile RT commute, but there are many times when I charge at home as well - at about 6kW -- and it's been a big help to charge as quickly as possible. If I had only a 20 amp supply at home like you're considering, given my usage, I think I could make it work with a little extra planning on my part.
         
      • Matthew Morgan

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        I would stick with the 20 amp until your driving situation changes. When you start driving electric, you will notice all the available spots to charge throughout the city if you needed to.
         
      • Mark C

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        If I understand correctly, 240v x 20A is 4.8kWh, less a bit of inefficiency loss, maybe 4.5kWh per hour charging. I am estimating my usage / driving style should get about 3.5 miles per kWh. My round trip commute is 39 miles {rounded up to the next mile}, so I expect to only need 11.2kWh {rounded up} to replenish the typical days usage. Give or take a bit, 2.5 hours will do fine, because (1) my typical day is less than 20% of the estimated Model 3 range and (2) if I recharge most days, it will cover 99% of my outlier trips as well.
         
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        • 18M3

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          #11 18M3, Apr 6, 2017
          Last edited: Apr 6, 2017
          Your math is correct in principle, but in practice you'll have a limited number of options. For example, I have a 40 amp circuit that allowed me to install a 32amp EVSE wall charger. So I don't get 240V x 40A = 9.6kW. It never delivers more than 6.6kW.
           
        • MelindaV

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          So to @18M3's point, does Tesla have a UMC adapter for the 240/20A receptacle (nema 6-20)?
          Otherwise a WC can be set to use 240/20A
           
        • Mark C

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          Have I not allowed enough for efficiency losses? 240v x 32A = 7680, so what am I missing? Does your EV have a 6.6kW onboard charger that can't make use of every last bit of available power? I am trying to learn, here. My knowledge base on this topic is limited to mostly what others who own EV's share and studying the responses that appear credible, and I am flexible on my EV plans.

          Beyond that, I've been looking at the charge cable specifications on what comes with a Model S, and if we get the same performance charging setup in the Model 3 as they get in a Model S, I may not even need to buy a separate EVSE.
           
        • Badback

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          Unfortunately, if you try to move 20A through a 20A circuit breaker, it will trip. You need to allow for some headroom, say 10% or 2A. Your nominal voltage under load is probably closer to 220V. So, 220 x 18 = 3.96kW. Notice that I did not put an 'h' on the end of the units. Power is instantaneous, energy is over time.
           
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          • AEDennis

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            The limit there is the Leaf. Newer ones are at 6.6kW and older ones are at 3.3kW.

            If you plugged in a Tesla on that plug, you would get the 32A... That's well within the spec of a single charger legacy Model S, or a standard option current Model S or Model X (as well as the Roadster's 16 kW onboard charger.)

            Not currently, 5-20, or 6-15, no 6-20.

            See shop.tesla.com
             
          • Ev43

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            Thank you one and all for the insights. This is a smart and friendly forum!

            Ev
             
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            • Les Inanchy

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              Although I did reserve a model three on March 31, 2016, I ended up buying one of the last model S 60s with the upgradable battery and took delivery on March 31, 2017. My wife is the primary driver , But her commute is only about 4 miles each way. We've been plugging it into a 120 V receptacle on the side of the house and at three or 4 mph charge, it's always ready to go the next day we did manage to get one of the last cars with unlimited supercharger included. My neighbor bought a Chevy bolt, and he charges it up at the local Whole Foods supermarket, which has a very low cost charging station. Because we had enough capacity on our 200 amp panel, I added a 240 V receptacle in the driveway and we can charge at about 25 mph rate.
               
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              • arnis

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                You will be fine. Just be sure it is 240V.
                Also take note that Model 3 will require much less energy per distance traveled than Model S and
                Model X requires considerably more energy per distance traveled than Model S. Therefore Model 3
                will need the least amount of amps/hours to charge if all else is kept the same.

                I have 16Amp/230V connection (3kW) with my Leaf and doing 20 000 miles annually, no problem.
                One thing you might give up with 20amp connection is doing all charging within cheapest electricity.
                It might take longer than few hours of cheapest off-peak period offers.

                If, years later, you actually will have problems with that you can get an EVSE equipment that monitors your
                electrical panel load and adjusts charging speed accordingly. It's better to have smarter charging protocol rather than
                one-time expensive upgrade.
                 
              • TrevP

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                We have a full gas range so there's 40amps we're not using and we hardly ever use our dryer and certainly not a night. We should be able to run our WC on a 50-60 breaker and not worry.
                 
              • Watts4me

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                I hope the model 3 lets us program when to start charging. If that's the case then you can have a higher amp for just that plug. And program the car to start charging at night when no other appliance is being used.
                 
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