Daytime Running Lights - Who is in favor?
Active Enthusiast
Joined: Jun 2008
Posts: 127
From: New Jersey. Land of high auto insurance and pollution.
Re: Daytime Running Lights - Who is in favor?
You won't find DRL on my car either.
I even switched to LED tail-lamps.
Let's say that saves me 50 watts.
That's one-quarter mile of "free" gas per hour.
Use 35 MPG as an average.
Use 50% driving at night.
That's 357 "free" miles worth of gas each 100,000 miles. ( if 50,000 are at night ).
Not huge, but not insignificant either.
DRL would be about double that, or cost you about 700 miles every 100,000.
( you'll buy 2 more tanks every 100,000 miles )
I even switched to LED tail-lamps.
Let's say that saves me 50 watts.
That's one-quarter mile of "free" gas per hour.
Use 35 MPG as an average.
Use 50% driving at night.
That's 357 "free" miles worth of gas each 100,000 miles. ( if 50,000 are at night ).
Not huge, but not insignificant either.
DRL would be about double that, or cost you about 700 miles every 100,000.
( you'll buy 2 more tanks every 100,000 miles )
2 X 30 Red LED 5W Brake Lights $19.00
4 X 24 Amber LED 5W Blinker Lights $30.00
Tax $3.43
Total $52.43
Paying $19.57 to reduce my carbon footprint by 10/gal of fuel burned and take money away from big oil and OPEC....priceless
Or I could use it to offset the reduction in FE caused by activating DRL
Thread Starter
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Ridiculously Active Enthusiast
Joined: Apr 2008
Posts: 895
From: Los Angeles
Re: Daytime Running Lights - Who is in favor?
Ok, so @ 35 MPG 357 "free" miles would be about 10/gal of free gas @ $3.50/gal (because we all know its going to go back up) is a $35.00 savings over 100,000 miles or 6 years based on our average miles per year.
2 X 30 Red LED 5W Brake Lights $19.00
4 X 24 Amber LED 5W Blinker Lights $30.00
Tax $3.43
Total $52.43
Paying $19.57 to reduce my carbon footprint by 10/gal of fuel burned and take money away from big oil and OPEC....priceless
Or I could use it to offset the reduction in FE caused by activating DRL
2 X 30 Red LED 5W Brake Lights $19.00
4 X 24 Amber LED 5W Blinker Lights $30.00
Tax $3.43
Total $52.43
Paying $19.57 to reduce my carbon footprint by 10/gal of fuel burned and take money away from big oil and OPEC....priceless
Or I could use it to offset the reduction in FE caused by activating DRL
Without DRL - 100000 / 30.6 = 3257.33 gallons of fuel.
With DRL - 100000 / 30.55 = 3262.11 gallons of fuel.
The difference is 4.78 gallons of gas over a distance of 100 thousand miles.
At $7 per gallon that is $33.46.
At $3.5 per gallon that is $16.73.
Cost of knowing that people can better see and avoid my FEH because of DRL = Priceless.
What cost do you place on the lives of your family members?
I'm using numbers provided in this thread that say using headlights takes up .9 MPG, and since DRL use 50% of the power, that means they use up .45 MPG.
Last edited by stevedebi; Nov 20, 2008 at 09:19 AM.
Ridiculously Active Enthusiast
Joined: Aug 2006
Posts: 859
From: Waterloo, ON
Re: Daytime Running Lights - Who is in favor?
In post #8 twolostminds said that the DRLs use 50% voltage at 50% duty cycle. Assuming that this is correct:
(1) the 50% voltage results in 25% of the power (the power is V^2/R, and assuming that the lamps' resistance R stays the same at the reduced voltage {this is approximately true}, the power drawn goes down by a factor of 4 when the voltage goes down by a factor of 2);
(2) the 50% duty cycle means that this reduced power is drawn for only half the time, a power reduction by a factor of 2;
(3) consequently, the DRLs draw 1/8 the power that the headlamps draw when fully on.
Your calculations should thus be based on a power reduction by a factor of 8.
Stan
(1) the 50% voltage results in 25% of the power (the power is V^2/R, and assuming that the lamps' resistance R stays the same at the reduced voltage {this is approximately true}, the power drawn goes down by a factor of 4 when the voltage goes down by a factor of 2);
(2) the 50% duty cycle means that this reduced power is drawn for only half the time, a power reduction by a factor of 2;
(3) consequently, the DRLs draw 1/8 the power that the headlamps draw when fully on.
Your calculations should thus be based on a power reduction by a factor of 8.
Stan
Thread Starter
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Ridiculously Active Enthusiast
Joined: Apr 2008
Posts: 895
From: Los Angeles
Re: Daytime Running Lights - Who is in favor?
In post #8 twolostminds said that the DRLs use 50% voltage at 50% duty cycle. Assuming that this is correct:
(1) the 50% voltage results in 25% of the power (the power is V^2/R, and assuming that the lamps' resistance R stays the same at the reduced voltage {this is approximately true}, the power drawn goes down by a factor of 4 when the voltage goes down by a factor of 2);
(2) the 50% duty cycle means that this reduced power is drawn for only half the time, a power reduction by a factor of 2;
(3) consequently, the DRLs draw 1/8 the power that the headlamps draw when fully on.
Your calculations should thus be based on a power reduction by a factor of 8.
Stan
(1) the 50% voltage results in 25% of the power (the power is V^2/R, and assuming that the lamps' resistance R stays the same at the reduced voltage {this is approximately true}, the power drawn goes down by a factor of 4 when the voltage goes down by a factor of 2);
(2) the 50% duty cycle means that this reduced power is drawn for only half the time, a power reduction by a factor of 2;
(3) consequently, the DRLs draw 1/8 the power that the headlamps draw when fully on.
Your calculations should thus be based on a power reduction by a factor of 8.
Stan
OK, lets try a calculation. Assume I get 30.6 MPG on my 2008 AWD.
Without DRL - 100000 / 30.6 = 3267.33 gallons of fuel.
With DRL - 100000 / 30.59 = 3269.98 gallons of fuel.
The difference is 1.06 gallons of gas over a distance of 100 thousand miles.
At $7 per gallon that is $7.44.
At $3.5 per gallon that is $3.71.
I'm not sure that $3.71 will buy even a cup of Starbucks!
Does this sound like better math?
Active Enthusiast
Joined: Jun 2008
Posts: 127
From: New Jersey. Land of high auto insurance and pollution.
Re: Daytime Running Lights - Who is in favor?
Please dont assume. I received this information from someone who seems knowledgable BUT since I didn't read it in a manual myself, I always encourage 2nd and 3rd parties confirming the informaiton.
Joined: May 2005
Posts: 2,468
From: Jupiter, FL
Re: Daytime Running Lights - Who is in favor?
In my '09 FEH tonight, I noticed with the lights on I would lose almost 1% of my SoC every few miles. Just as I was getting prepared to go EV at 42% SoC, all of a sudden I would lose .9% SoC to the heavy demand of the running lights to the 12V battery. The '09 operates differently than my '05 because I've never noticed this quick drop in SoC before. There is definitely a drop in mileage with the regular running lights, but I never thought it was this big until driving my '09.
GaryG
Last edited by GaryG; Nov 20, 2008 at 07:35 PM.
Pretty Darn Active Enthusiast
Joined: Apr 2006
Posts: 464
Re: Daytime Running Lights - Who is in favor?
It would also be a good idea not using the auto headlights. I find it annoying that they turn on going under an underpass. I just turn on my headlights the old fashion way.
Enthusiast
Joined: Apr 2008
Posts: 45
Re: Daytime Running Lights - Who is in favor?
Here in Canada day headlamps are required and have been for years. I think they are great and on single lane highways, save many lives. Most vehicles these days have sep day running lamps that use less E than full headlamps.
Hybrid and Ethanol Expert
Joined: Mar 2005
Posts: 3,616
From: All over the Central U.S.
Re: Daytime Running Lights - Who is in favor?
Use logic here please!At one-eighth the power, you would not be able to SEE the lamps...
These are DAYTIME running lamps, after all!
Everyone, print this message since it is historical...
I actually AGREE with GaryG on this one.
80% is the only figure that makes any sense for DRL.
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Joined: Nov 2008
Posts: 729
From: Coquitlam BC, Canada (Greater Vancouver area)
Re: Daytime Running Lights - Who is in favor?
As has been mentioned, in Canada DRL's are the legislated. For me, being Canadian, that's the bottom line. Outside of Canada, I think they're a good idea: they use a lot less juice than the old ploy of just turning on your headlights.
Sort of off-topic: have you ever been accross the intersection from a vehicle which has it's front turn signals tightly integrated next to it's headlights? Sometimes the proximity and brightness of the headlights make it near impossible to see if the turn signal is indeed pulsing. I hate that.
Sort of off-topic: have you ever been accross the intersection from a vehicle which has it's front turn signals tightly integrated next to it's headlights? Sometimes the proximity and brightness of the headlights make it near impossible to see if the turn signal is indeed pulsing. I hate that.
