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Less electrical load saves gas... right?

Discussion in 'Prius v Accessories and Modifications' started by scottmcphee, Apr 12, 2013.

  1. scottmcphee

    scottmcphee Junior Member

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    In the theme of power saving, LED's instead of incandescent bulbs are better. Lessening the overall electrical load placed on the alternator will use less gas.​
    Here's a question for all hypermilers to think about on their commute. If the duty cycle of the signal flasher was changed from the stock 50/50 (percentage on to percentage off time ratio) to something having less on time in proportion to off time... it would draw less average power. Over the life of the car, and if you're a diligent signaller ;);) ... it might even save a little gas. ​
    I was wondering if there'd be interest in having a "Prius version" flasher that features say, 40% on 60% off duty cycle per blink? (While maintaining regular flash frequency of around 90 cycles per minute). This represents a 20% power savings and would still be legal. ​
    Any math whiz take a guess how much this might save in gas over the life of the car?​




    Read more: http://priuschat.com/threads/turn-signal-flasher.96742/#ixzz2QGH7k8F5
     
    #1 scottmcphee, Apr 12, 2013
  2. jdenenberg

    jdenenberg EE Professor

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    Our Prii use about 300 watt-hours of gasoline energy per mile. You can use this to estimate MPG savings from lowering electrical energy use, but remember that there is an inefficiency factor (about 50%) in generating 12v power vs direct use of mechanical energy. So if you run a thermo-electric cooler (as I do on some road trips, this is about a 4 amps electrical load or about 50 watts) while traveling at 60 miles per hour (18 kw-hrs per hour) the MPG cost is about 50*2/18,000 = 5.5% (the 2 is that 50% factor). This is a reduction in MPG of 2-3 miles/gallon in a Prius.

    Your idea to reduce the duty cycle of the turn signal is a negligible savings in energy, but LED headlights would be a noticeable savings in MPG, but a significant first cost.

    JeffD
     
    #2 jdenenberg, Apr 12, 2013
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    In reply to your title: Yes, but never compromise safety or durability for MPG. Not running A/C will save electricity, but the cabin A/C also cools the HV Battery, so you may need a new battery sooner. Running headlights lowers MPG but you are hit by oncoming traffic less.
     
    #3 JimboPalmer, Apr 12, 2013
  4. skwcrj

    skwcrj Member

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    The problem is that external factors (weather, traffic, road surface/conditions, elevation changes, mechanical issues, etc.) and driver factors (speed, driving techniques, hypermiling, etc) tend to have a more significant influence with mpg. Saving a few milliwatts would be fairly insignificant if you "drive it like you stole it" or your 12v is on it's last leg.
     
    #4 skwcrj, Apr 12, 2013
  5. cwerdna

    cwerdna Senior Member

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    OP, do you have a Prius v wagon?
     
    #5 cwerdna, Apr 12, 2013
  6. scottmcphee

    scottmcphee Junior Member

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    nope
     
    #6 scottmcphee, Apr 12, 2013
  7. cwerdna

    cwerdna Senior Member

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    Then why post in the Prius v wagon area?

    BTW, Prius has no alternator. There is a DC to DC converter inside the inverter that powers the 12 volt bus.
     
    #7 cwerdna, Apr 13, 2013
  8. scottmcphee

    scottmcphee Junior Member

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    Good point about the alternator, my duh.

    I actually didn't mean to hit the v forum specifically, I missed, I wanted to hit the most general forum... (new here).
     
    #8 scottmcphee, Apr 13, 2013
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