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single charger... unable to pull more than 40A?

Discussion in 'Model S: Battery & Charging' started by NeedToDrive, Dec 3, 2016.

  1. NeedToDrive

    NeedToDrive Member

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    So I may of made an mistake. For the last 3+ years I've been happily using the mobile connector to charge my car. It has worked well and I typically pull 40A at 237V. The car is equipped with the standard single charger. This fully charges the battery during the off-peak evening rates.

    Every once in a while I go for a road trip to my sisters house. This depletes my SOC to less then 8% so I really can't do much when I get there other than to plug into a relatively slow 30A outlet. Recently I decided it would be great to install a connector at her house so I could visit more often and get a quicker charge that would allow me do some errands after a short time charging.

    My first inclination was to install a NEMA 14-50 and charge at 40A as I do at home. The outdoor rated box cost me $29 plus a 50A fuse, wires etc. However, given that the wall connectors have dropped in price I thought it would be worth it to be able to pull 48A and reduce my wait time by an additional 20%. I was told 48A was the limitation for a single charger by the parts department representative. So I bought a 60 fuse, increased the wire size to #6 AWG and paid the $550+tax for the wall connector... I planned to return the NEMA 14-50 box.

    I spend all morning yesterday installing said equipment. Since my sister has a surface mount main breaker panel, a couple of free breaker slots, and the panel just happens to be right next to the driveway, it wasn’t that hard to a drop conduit directly from the panel to the Tesla wall connector junction box. The Tesla 24' cord was more than long enough. In any case, I plugged it in … just to find I was only drawing 40A!!!

    I called the Tesla information line and was told that the reason I couldn’t get the full draw was her voltage is less than 240V (The car indicated 230V or so). To get 48A I’d need to be at 240V. This don’t make sense to me as a lower voltage would imply a higher amperage for an equivalent power draw.

    Does any one know what the limitation is? Is the onboard charger limited by current or power? If voltage is the limitation, shouldn’t I get 230 * 48 = 11.04kW? If the charger is limited by power shouldn’t I get 10,000 / 230 = 43.5A? I double checked my wall connector settings and confirmed that the rotary setting is to ‘9’ which allows 48A (the #1 DIP setting is down to indicate 240V or less). Heck with AWG#6 I believe I ought to be able to pull 60A per code (THHN 75A wire derated etc.) but I was being conservative.

    The bottom line is that I don’t seem to be doing any better at all with a wall charger than using my mobile connector. I’m wondering if that is a problem with the car/charger or the wall connector. If either is a fundamental limitation then I’m thinking I’ll return it and replace with the much less expensive 14-50.
     
  2. efusco

    efusco Moderator - Model S & X forums

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    The current version of the charger is 48 amps and upgradeable (via software) to 72 amps. If you've had your car for 3 1/2 years you have a single 40amp charger, upgradable to dual chargers for up to 80amp charging.
     
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  3. TexasEV

    TexasEV Well-Known Member

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    The first person you spoke to must have assumed you were asking about a current car, not a 3 year old one that has a 40A charger. The second person you spoke to gave incorrect info (not an uncommon occurrence at Tesla), or maybe there was just miscommunication. If there is a voltage drop the car will drop the charging rate from 40 to 30A for safety reasons. That's probably what he was referring to, but that wasn't your question.
     
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  4. NeedToDrive

    NeedToDrive Member

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    So the onboard charger design changed? I went back and looked at my original paperwork: It lists a "10 kW on-board charger". I didn't see a 40A limitation. Do you know where I can get the technical specs on it? Other than the reality I face :(, it would be nice to confirm.

    BTW, I also was very clear with both Tesla folks that I had one of the original cars from early 2013. I was aware that sometimes the SC reps need a little help. What's even more interesting is that when I bought the HPWC they had to record my VIN, so the parts guy must of known if there was a limitation.
     
  5. efusco

    efusco Moderator - Model S & X forums

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    The 10kW is the 40amp charger. And I'm sure you were very clear, but most likely the tesla folks you spoke with have never sold a car with the old 40amp charger. So yes, the design changed about the time the Model X came out.
     
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  6. st50maint

    st50maint Member

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  7. TexasEV

    TexasEV Well-Known Member

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    To further clarify, 40A X 250V = 10,000W (10kW). They're also limited to 40A, so you can't get more amps at a lower voltage. Since most service is going to be 240V or lower, it's really a 9.6kW charger and that's rounded up to 10.
     
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