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Typical Home Charge Rate

Discussion in 'Charging Standards and Infrastructure' started by nwdiver, Nov 29, 2014.

?

Default Home Charge Rate

  1. <=10 amps (~2.5kW)

    2 vote(s)
    2.7%
  2. 20 amps (~5kW)

    5 vote(s)
    6.7%
  3. 30 amps (~7.5kW)

    17 vote(s)
    22.7%
  4. 40 amps (~10kW)

    29 vote(s)
    38.7%
  5. 50 amps (~12.5kW)

    1 vote(s)
    1.3%
  6. 60 amps (~15kW)

    3 vote(s)
    4.0%
  7. 70 amps (~17.5kW)

    2 vote(s)
    2.7%
  8. 80 amps (~20kW)

    16 vote(s)
    21.3%
  9. I let my utility decide via software

    0 vote(s)
    0.0%
  1. nwdiver

    nwdiver Active Member

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    Forgive me if this has already been discussed... I'm curious as to what most people have their cars set to for the default charge rate at home.
     
  2. bollar

    bollar Disgruntled Member

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    80 amps. Might as well...
     
  3. nwdiver

    nwdiver Active Member

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    I've got dual chargers but I scale mine back to 20amps to reduce line losses...
     
  4. ecarfan

    ecarfan Well-Known Member

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    80A for my S. No compelling reason not to, IMO.
     
  5. jpasqua

    jpasqua P19325

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    80 amps with an HPWC.
     
  6. nwdiver

    nwdiver Active Member

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    Hmmm.... I think at least 3 people missed the poll :wink: or they're LIERS! :mad:......... :biggrin:
     
  7. liuping

    liuping Active Member

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    Is that really more efficient? I thought charging at a higher rate lost less. Also, slower charging means running the battery cooling longer, etc.
     
  8. thecloud

    thecloud As rhythm raced inside, the ship came alive

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    Curious about that and whether there is an "optimal" amperage for charging. I primarily charge from a NEMA 14-50 outlet and have been using the default 40A setting to minimize charging time. Recently I've been experimenting with dialing it back as the UMC cable gets quite warm while drawing 40A continuously (something I'm sure everyone else has discovered). Using 32A or less seems to solve that problem. So, assuming there is plenty of time overnight, is 20A going to be more efficient than 30A in terms of minimizing both energy draw and energy loss? The UMC manual says that the outlet must be rated for at least 15A, so that's probably the lower bound, but I always thought that was supposed to be much less efficient than a higher setting.
     
  9. nwdiver

    nwdiver Active Member

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    The lower bound is 5 amps... electrically lower is ALWAYS more efficient; I'm not sure about the chargers themselves... there might be a 'sweet spot' where 20 amps is more efficient than 10. Line losses are Current² x Wire resistance; so the amount of energy lost to heat increases exponentially with higher current. You loose 4x as much energy at 80 amps that you loose at 20 amps.

    I've also heard rumors that certain charge levels are better for the battery than others but that's likely temperature dependent and I've never seen anything 'official'.

    Lower can also mean you don't run the battery cooling AT ALL... as far as I'm aware battery cooling only runs when its needed. I could be wrong... the pump might circulate coolant continuously but the fans certainly don't run when I charge @ 20 amps unless its REALLY hot outside.
     
  10. bollar

    bollar Disgruntled Member

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    Would love to see this data on the S! It exists for the Roadster and the results were...

    Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog
     
  11. nwdiver

    nwdiver Active Member

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    Yeah... I suspect there's a sweet spot... a rectifier and inverter operate in a very similar way and inverter efficiency curves look like this;

    solar-inverter-peak-efficiency1.jpg

    That's another reason I picked 20 amps vs 10 or 5... I wonder if Tesla is listening... wouldn't be the first time I got a call from customer service in regards to a post :smile:
     
  12. omarsultan

    omarsultan Active Member

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    80A - paid for it, might as well use it.
     
  13. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I have 80 Amps available, but charge at 56 Amps for half the resistive power everywhere and sqrt(2) the total resistive losses for the charge. Using more than 40 Amps, tests both chargers in the car.
     
  14. nwdiver

    nwdiver Active Member

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    Hmmm... that's a good idea... the car doesn't split it? If I charge @20 amps it's 20/0 not 10/10?
     
  15. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Put in 30, but actually I charge at 33. Even an 33, once in a while the city electricity causes it to go back to 30. This is a problem in this area, not with my house. If I charged at 40 it would jump down to 30 50% of the time rather than once or twice per month.
     
  16. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    I usually charge at 60A. I use 80A when the soc is low and I need to complete my charge within the 4-hour ultra off peak window.
     
  17. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    If you have dual chargers, the car uses one module up to 40 Amps and then splits the load from 41 to 80 Amps.
     
  18. SW2Fiddler

    SW2Fiddler Bannd Member

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    There are probably sweet spots for each type of connection equipment... (Must be a resistance difference between, say, 40A thru a UMC and 40A thru a HPWC)
    Leads me to ask, a bit OT, but is there a premium brand of NEMA 14-50 outlet with superior contacts? That connection is a factor we can do something about.
     
  19. Rockster

    Rockster Active Member

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    For this reason, I charge at 42 amps. That way I'm constantly testing both chargers.
     
  20. mspohr

    mspohr Active Member

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    #20 mspohr, Nov 30, 2014
    Last edited: Dec 2, 2014
    Edited this to correct my error which was wrong information.
    As Cottonwood has pointed out, the power loss is i^2r so it is not linear. You will have lower line loss by charging at a lower current.
     

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