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What is the most efficient charging power?

Discussion in 'Model S: Battery & Charging' started by zdre, Aug 10, 2013.

  1. zdre

    zdre 40kWh Model S P6415

    Jan 18, 2010
    St. Louis
    Does anyone know what is the most efficient charging power for a single charger?
    From my experience with computer power supplies, the highest efficiency is achieved at around 50% load.
    The issue is that we don't know how much the Model S charger's max load of 10kW is already de-rated from the real maximum.
    It would be great if Tesla provided an efficiency curve for the Model S chargers like the one below:

  2. schueppert

    schueppert Member

    May 15, 2013
    Houston TX
    I have seen charts like that for PC power supplies too. I believe more efficient modern designs tend to retain their highest efficiency up to much higher loads. In Model S you also have to consider that charger losses are about equal in magnitude to internal battery losses, and these battery losses are probably proportional to current. I suspect these two effects more or less cancel out so that efficiency doesn't vary too much with charging power. But as you say, it would be nice to have some real data.
  3. stopcrazypp

    stopcrazypp Well-Known Member

    Dec 8, 2007
    Your overall charging efficiency will depend on your wiring for your charger too (since you care about from the meter to your car, not just from the charging socket). So even if you find the most efficient point for the onboard charger, that's not necessarily the same overall.

    So it'll probably trend somewhere slightly lower than the most efficient charging load.
  4. markwj

    markwj Moderator, Asia Pacific

    Apr 10, 2011
    Hong Kong
    #4 markwj, Aug 10, 2013
    Last edited: Aug 10, 2013
    This has been discussed in a few threads.

    Conclusion was that you need to balance the efficiency of the charging system against the use of HVAC and fans during charging. Lower currents are more efficient from an electrical losses point of view, but HVAC/fan losses are greater. Depending on individual situation, electrical losses from meter to vehicle may also be significant,

    Charging in High Temperature environments 13A vs 32A vs 70A: cost of air conditioning
    You might consider charging slower

    (Edit: to add links to relevant threads)

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