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Destination Chargers - kWh to Miles Charging

Discussion in 'Model 3: Battery & Charging' started by PRSIST, Aug 26, 2017.

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  1. PRSIST

    PRSIST Member

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    I’ve been looking at Tesla destination chargers and they usually show either 8 kWh or 16 kWh. Anybody know how this converts to miles per hour of charge?


    If I arrive at my hotel for a night’s stay and I have 62 miles left and want to charge up to 80% of my 310, or 248 miles, I need to add 186 miles. If I knew the hotel has a 16 kWh charger and that it puts X number of miles on my car per hour, I would of course be able to time my charging for the night.


    Thanks for any help.
     
  2. MyJoule

    MyJoule Member

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    The car will tell you when you plug it in the charge rate, it might be a 16KW charger, but it might not get 16KW. However if it does,. basically, 16KW will get you about 48miles per hour range added.. YMMV. I usually calculate roughly 330wh/mile on the charging side of the equation ( this sort of accounts for the losses in the charging system/cables etc) One more point- if you are on a supercharger the same thing applies: it takes about 330Wh to add a mile of range to an S85. again YMMV
     
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  3. PRSIST

    PRSIST Member

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    Thank you. The light bulb just appeared. 16,000,000 Wh/330 Wh = 48 miles.
     
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  4. David29

    David29 Member

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    One way to get a feel for it is to look at Tesla's web site for their charging calculator, which is here:
    Home Charging Calculator

    In essence the website says that:
    A Model S with a 48 amp charger can charge at 29 miles/hour if the source supplies 40 amps, and at 52 miles/hour if the car has the 72 amp charger and the source is a 90-amp circuit. There are also values for other charger configurations and (lower) values for Model X. Model 3 might be different.

    Those values of 8 kw (not kwh) and 16 kw for the destination chargers are a bit confusing, I think. But I agree with you that that is how they are listed. (I have also seen 13 kw for a few places.) I think the values might depend somewhat on when the chargers were installed as well as how large a circuit they are on.

    My own Tesla Wall Connector is on a 50-amp circuit so it can charge at a maximum of 40 amps. If the voltage is nominally 240 V, that would be 9.6 kw, and the single charger on my car is rated for that amount. I think that is probably the lowest rating Tesla would have allowed for a destination charger. So I suspect the 8 kw figure is a conservative version of the 9.6 kw rating, to reflect possible lower supply voltage. For my Model S, the 40 amps from my home WC adds roughly 30 miles of range for each hour of charging.
    Tesla's web site says that the Wall Connector can provide up to 72 amps for cars equipped with the appropriate charger, so at 240 volts that would be 17 kw. But older cars that were equipped with the second 40-amp charger could expect to charge at 80 amps or 19.2 kw.
    Guessing here but I imagine what Tesla has done is to standardize on the 8 kw and 16 kw figures as representative of more realistic voltages and that they represent 40-amp or 80-amp configurations. Or possibly 40-amp and 72 amp. Although I have charged at Tesla destination chargers a couple of times, I can only charge at 40 amps so I may not have hit the local limit.

    Hope I have not confused you more than I helped!
     
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  5. MyJoule

    MyJoule Member

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    One more thing to add to the confusion- many destination chargers are 208V not 240V- so they won't be quite as many KWH charging. It has to do with 3 Phase industrial power. where a home is line to line 240V. So 40 Amps and 208V get's you about 8.3KW vs 9.6KW- You really can tell by looking at the dash when you plug in and the charge starts- the voltage and current are reported. Multiply them together, and divide by 330 that will get you close- One more caution, as the car nears full, the charge current will taper off, sort of like it does at a supercharger. so the range added per hour drops. That should make sure you are thoroughly confused.
     
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  6. boaterva

    boaterva Supporting Member

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    That's actually 16 MWh but we know what you meant. :D

    I just multiply by 3 for a rough estimate.
     
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  7. Glade_EV

    Glade_EV Member

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    I'm thinking that the limitation will be with the onboard charger. The M3 LR specification lists 37 miles per hour for "Home" charging (which I would interpret as coming from the L2 charging specification). That sounds pretty close to the 40 amp case; ie looking for 16 kW destination chargers won't buy you much (if anything).
     
  8. Runt8

    Runt8 Member

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    According to Tesla the LR version will charge at 40A at home, but there have also been unconfirmed reports of it having a 48A charger. So it’s possible that Tesla was using the most common case of people charging with a 14-50, but if they use a HPWC then they might get a little more.
     
  9. cpa

    cpa Active Member

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    Is not the Model 3 allegedly to be able to go a little further on a kWh? So, while we use ~3-4 miles per additional kWh for the S and X, the Model 3 might be closer to ~4-5 miles per added kWh.

    But I think it will suffice to say that regardless of voltage (208 v 240) and regardless of amperage (32/40/48) an eight-hour charge will be able to get a 10% battery back to 90% or pretty gosh darn close.
     
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  10. boaterva

    boaterva Supporting Member

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    Not sure how it's 'unconfirmed' when that info came from the charging group at Tesla. The 40 Amp is just Tesla PR about what you get using a 14-50 outlet at home. Upselling the S and X, as usual. Seriously!

    Like a lot of other details, they didn't/aren't letting things out on purpose. Remember the base configuration and the front heated seats? Still not clear if you don't believe that screen shot from M3OC/Trevor. :D
     
  11. Runt8

    Runt8 Member

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    It came from some random guy on the internet who claims it came from the charging group. People should have more confirmation than that if they are basing a $500 decision on it. Official confirmation from Tesla, or at the very least video from an owner showing it charging at 48A using a HPWC.
     
  12. Cosmacelf

    Cosmacelf Active Member

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    Bottom line is that an 8kW destination charger will do what you want and more on an overnight charge. It'll get you about 25 miles of range per hour.
     
  13. SageBrush

    SageBrush Active Member

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    Throw that bulb away.

    If your car/driving-habits use 330 Wh/mile, that works out to ~ 3 miles per kWh ( 1/0.33)

    An 8 kW charger means the car battery takes in ~ 8 kWh an hour so about 8 kWh*3 miles/kWh = 24 miles an hour
    A 16 kW charger means the car battery takes in ~ 16 kWh an hour so about 16 kWh*3 miles/kWh = 48 miles an hour

    Caveat: just because a charger is rated for X kW does not guarantee that rate. Plug in and check the actual rate.
     
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  14. jsmay311

    jsmay311 Member

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    Someone found a decently-legible photo of a Model 3 Long-Range EPA (Monroney) sticker showing an efficiency of 126 MPGe, which equates to approximately 0.267 kWh/mile.

    So that'd be 1/0.267 = 3.75 miles per kWh *from the wall/charger*.

    And presumably the standard range model should be a bit more efficient.

    ( Monroney Stickers ? )
    [​IMG]
     
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  15. SageBrush

    SageBrush Active Member

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    The combined city/highway Monroney for the Model S is 103 MPGe , so CPA is correct is estimating about a 30% better miles/kWh in the Model 3
     
  16. TexasEV

    TexasEV Well-Known Member

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    I'm the "some random guy on the internet" who posted that. In my previous 5,000+ posts on this site since 2013 I don't think I've given anyone misinformation, so that post should have a little credibility.
     
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  17. Runt8

    Runt8 Member

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    I did not mean to imply that you were lying or misleading us about your conversation - if it came across like that then I apologize. Based on your posting history I'm more than willing to take you at your word. The problem comes when people then take that information and parrot it back like it's a confirmed fact without any indication of where it came from. I can easily see someone deciding to purchase the HPWC because they want to charge at a higher level than is possible with the 14-50. They should know that, at this point, the 48A charger hasn't been confirmed.
     
  18. PRSIST

    PRSIST Member

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    According to Tesla's release information, Long Range Battery - "Home charging rate: 37 miles of range per hour (240V outlet, 40A).

    I just bought the HPWC because I have read so much about the 48A charging capability. I guess that's a problem, reading too much stuff. I won't be opening the box when it arrives until I confirm that the car has a 48A charger.

    It's really not any cheaper to get a second Corded Mobile Connector ($520) just so I can keep the one that comes with the car.

    IF, the car only takes 40A, then putting anything except a 50 amp wall outlet in, is just a waste of money.
     
  19. boaterva

    boaterva Supporting Member

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    You can run the HPWC at any level, so it will work for any car, on any circuit. You may get another Tesla later... :D

    As I said somewhere, their '40 Amp' doesn't say it has a 40 Amp charger, it says using a normal outlet, since there is no larger 'outlet' than a 14-50 usually. You need an HPWC.

    I really don't think that email from Tesla Charging was a scam, either. But if someone wants physical proof, we'll have it when someone with an HPWC gets a premium 3 in a few months (ours won't be until probably January).
     

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