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Switch off headlights to save power?

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Kipernicus

Model S Res#P1440
Dec 2, 2009
1,256
141
Belmont, CA
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
 
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

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:
 
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. :)
 
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)

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.
 
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.
 
Great info! Thanks everyone!

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

Headlamps on Motor Vehicles
24400. (a) A motor vehicle, other than a motorcycle, shall be:
(1) Equipped with at least two headlamps, with at least one on each side of the front of the vehicle, and, except as to vehicles registered prior to January 1, 1930, they shall be located directly above or in advance of the front axle of the vehicle. The headlamps and every light source in any headlamp unit shall be located at a height of not more than 54 inches nor less than 22 inches.

(2) Operated during darkness, or inclement weather, or both, with at least two lighted headlamps that comply with paragraph (1).

(b) As used in paragraph (2) of subdivision (a), “inclement weather” is a weather condition that is either of the following:

(1) A condition that prevents a driver of a motor vehicle from clearly discerning a person or another motor vehicle on the highway from a distance of 1,000 feet.

(2) A condition requiring the windshield wipers to be in continuous use due to rain, mist, snow, fog, or other precipitation or atmospheric moisture.

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