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HPWC 18kWh or should it be less

Discussion in 'Australia & New Zealand' started by Fantomsss, May 17, 2019 at 2:40 AM.

  1. Fantomsss

    Fantomsss Member

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    I'm a little confused. I’ve installed HPWC today and can see it doing 18kWh charge (inside the car). It is 2019 75D.

    Everywhere I look they talk about 16kWh on late model single charger. Is it real 16 and 18 showing in Tesla are fake? Or is this normal for Australia and I’m just seeing US numbers in other threads/websites?
     
  2. meloccom

    meloccom Moderator Aus/NZ

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    How many amps is your car reporting?
    If it’s 24A 3 phase that’s 240 x 24 x 3 = 17280W.
     
  3. cwerdna

    cwerdna Active Member

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    OP, if you're talking about charging rate, you're using the wrong units. That should be in kW, not kWh.

    kW and kWh are very different metrics. It's the same as confusing gallons with horsepower. Think of kW = horsepower, kWh = gallons.

    If one charges at 1 kW (or 1000 watts) for 6 hours, 6 kWh came out of the wall. If it's at 6 kW for 1 hour, it's also 6 kWh. If it's 1 watt for 6000 hours, it's also 6 kWh.

    Watts or kilowatts are measure of power. Watt-hours are a measure of energy.

    One pays for electricity at home in cents per kWh. In the US, there are a few utilities w/residential plans where they not only bill per kWh but also have demand charges (in kW), but that's rare and complicates calculations. (Demand charges aren't unusual on many commercial plans.)

    (BTW, 1 hp = ~0.746 kW. And, many .gov sites say 1 gallon of gasoline=33.7 kWh.)
     
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  4. Jays200

    Jays200 Member

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    Just to correct your units. Charging speed is described in kW, not kWh (which is battery capacity). A 100kWh battery could discharge at 100kW for an hour. Just to confuse further, a 100kWh battery, charged at a continuous 100kW, is charging at 1C. Which is very mild compared to when I charged my radio controlled electric helicopter LiPo batteries at 5C.

    To add to the above, if you have solar at home I sometimes see a line voltage of 250v which is 250v x 24A x 3phases=18kW.
    230v x 24A (amperage limit of the higher capacity "modern" onboard AC-DC charger) x 3 phase= 16.5kW, but I think there is a total power (kW) limit of the onboard charger irrespective of the line voltage although I'm not sure what that is. Older Teslas had dual 11kW chargers for 22kW (full 32A). This is about 100kms of added range per hour vs 70ish kms of added range per hour for the 24A charger.

    Confusing initially but obvious practically ;)
     
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  5. Fantomsss

    Fantomsss Member

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    Yep, you are all correct and thanks for pointing out the difference. Let me try again :)

    I got 75 kWh pack and seeing charging rate at 18 kW. It is indeed 3 phase at 24A. So it looks like it gets rounded up to the nearest higher number. Voltage, not sure but would assume ~ 240v plus/minus.

    Don’t have solar. Yet. ;)
     
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  6. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    What's your voltage? If you're getting over 240V you might be closer to 18kW with a bit of lucky rounding.
     
  7. Blue heaven

    Blue heaven Fair Dinkum Tesla

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    18kw is good for a late model S, you must have the HPWC mounted high on the wall.
     
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  8. conman

    conman Active Member

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    What you're seeing is that it is extremely common in Australia for the voltage to be above 240V. I've seen as high as 254V. This puts other electrical components at risk and wastes power in our houses, BUT your car can make the most of it and indeed it can go up to 18kW. Next time look at the reported voltage as well as the current.
     
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  9. paulp

    paulp Active Member

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    In SA, well at my house at least, the power is regularly well below 240v. 230v is often the number. I charge faster with solar as it increases the voltage
     
  10. Fantomsss

    Fantomsss Member

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    Ok I have checked. It starts out at ~ 249V and settles around 244-245V.
     
  11. conman

    conman Active Member

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    Power = V x I. Voltage at 245V x Current at (24 x 3 phase) 72A = 17.6kW. At 250V it's 18kW exactly.
     

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