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Switch off headlights to save power?

Discussion in 'Electric Vehicles' started by Kipernicus, Dec 11, 2009.

  1. Kipernicus

    Kipernicus Model S Res#P1440

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    Does anyone know if it is legal to switch off your headlights while waiting at a stoplight at night? I imagine every bit of power saved in an EV means more range.

    What about switching off headlights while in stop and go traffic and relying on DRL's or parking lights?

    Perhaps legality will vary from state to state. I'm in CA.

    Thanks
     
  2. bolosky

    bolosky Member

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    The Roadster low beams draw about 35W/side, or 70W total. One mile takes 250-300 Wh, so you'd have to turn the lights off for 3-4 hours to save one mile of range. You probably won't be stopped that long. :smile:
     
  3. mpt

    mpt Electrics are back

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    I'm going to recommend a no there. The battery pack is 55KWh, the headlights are 120w (60w each). That's about well, you'll be older by the time they run the battery down.

    From a financial point of view, the power consumed will be a fraction of the cost of a replacement light switch.

    And lastly, power saving; that's for gas cars more than electrics. Electrics are more efficient at turning energy into power for the light bulbs than burning gas on board to power those bulbs.

    So, in summary, no. :)
     
  4. edo

    edo Member

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    If you want to save power, shut off your heater... that's on the order of 1000 watts. (Then wipe your windshield with a rag instead of using the defogger)
     
  5. bolosky

    bolosky Member

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    Turning the heater on full blast seems to draw about 10 amps for me. The battery voltage is 350-400V depending on state of charge, so that's 3500 - 4000W. Now THAT makes a difference.
     
  6. TEG

    TEG TMC Moderator

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    Air conditioning is probably a similar energy hog.

    Supposedly the seat heaters use a tiny fraction of the main heater.
     
  7. mpt

    mpt Electrics are back

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    Heater is 4kW but is thermostatically controlled so, if you turn on the fan at full speed and heat up to full it works hard to keep up. If you lower it and reduce the fan speed it lowers the power consumption.

    Same with the ac, it's trying to get the radiator down to 1c. On a hot day that's hard and expensive, on a cool day the pump seldom starts.

    If you really want to save power, drive slowly.
     
  8. Kipernicus

    Kipernicus Model S Res#P1440

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    Great info! Thanks everyone!
     
  9. shark2k

    shark2k Member

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    Since you are in California I looked up the Motor Vehicle Code for you.

    Source: V.C. Section 24400 - Headlamps on Motor Vehicles

    Bolded part to me suggests that if you are in the motor vehicle and on the road (where you would actually be driving) you need to have your lights on.

    -Shark2k
     

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