Headlights affect on fuel mileage?

[likesmpg]

Purely out of curiosity, has anyone done a reasonable experiment to show the affect of having the headlights on fuel efficiency? Driving to work today I notcied my battery bar dropping more quickly than usual (it stays dark longer now). I turn mine on for safety of course but was wondering if anyone had any neat data? Thanks.

[CheepCheep]

<div class='quotetop'>QUOTE(likesmpg @ Aug 23 2007, 08:38 PM) [snapback]501286[/snapback]</div>

Purely out of curiosity, has anyone done a reasonable experiment to show the affect of having the headlights on fuel efficiency? Driving to work today I notcied my battery bar dropping more quickly than usual (it stays dark longer now). I turn mine on for safety of course but was wondering if anyone had any neat data? Thanks.
[/b]

Does the traction battery power the headlights?

If not, lights on would have a negligible effect on on mileage.

CC

[geodosch]

<div class='quotetop'>QUOTE(CheepCheep @ Aug 23 2007, 09:09 PM) [snapback]501301[/snapback]</div>

Does the traction battery power the headlights?

If not, lights on would have a negligible effect on on mileage.
[/b]

Regardless of which battery the headlights are powered from, that power was generated from the ICE, so the effect is still there, just as headlights on a conventional car are powered from the battery, and that power must be replaced by the alternator, which puts additional drag on the engine, which affects fuel economy. IOW, lights use power, which has gotta come from somewhere.

[brad34695]

<div class='quotetop'>QUOTE(GeoDosch @ Aug 23 2007, 09:35 PM) [snapback]501311[/snapback]</div>

Regardless of which battery the headlights are powered from, that power was generated from the ICE, so the effect is still there, just as headlights on a conventional car are powered from the battery, and that power must be replaced by the alternator, which puts additional drag on the engine, which affects fuel economy. IOW, lights use power, which has gotta come from somewhere.
[/b]

I agree, and I even go to the extreme of only using my turn signals when necessary. Meaning if I am waiting at a red light, I do not have them on and will put them on when the light turns green. Also, if I am in a designated turn lane I don't have them on as the direction I'll be moving in is already predetermined by the lane. Most importantly, I only run the A/C when my six year old son is in the car as that is the biggest killer of MPG. It's all in the life of a hypermiler.

[EricGo]

Headlights -- about 200 watts.

As for skimping on turn signals -- please, don't.

[ACORNBLUES]

Hello! Once the relays to the t.batt the a.batt (12V) is no longer used. The inverter supplies the 12V (also charges the a.batt).

side note: hid headlights uses less power than the halogen headlights.

[icarus]

<div class='quotetop'>QUOTE(brad34695 @ Aug 23 2007, 06:56 PM) [snapback]501325[/snapback]</div>

I agree, and I even go to the extreme of only using my turn signals when necessary. Meaning if I am waiting at a red light, I do not have them on and will put them on when the light turns green. Also, if I am in a designated turn lane I don't have them on as the direction I'll be moving in is already predetermined by the lane. Most importantly, I only run the A/C when my six year old son is in the car as that is the biggest killer of MPG. It's all in the life of a hypermiler.


[/b]

No offence but you are one of the sources of my worst driving agrivation! By not turning you turn signals on until the light turns green, no one behind you can have the option of avoiding you by changing to another lane! As I am oft quoted as saying, "Turn signals are for what you are GOING to do rather than what you just DID!"

As the other poster says, PLEASE, for the benefit of all of us, start using the signals. I'll even send you the
$.20 you might save every year!

Icarus

PS My other driving nightmare is the guy not bothering to pass someone while driving in one of the left lanes of the freeway, plugging it up for all the rest of us!

[geodosch]

<div class='quotetop'>QUOTE(icarus @ Aug 23 2007, 11:11 PM) [snapback]501365[/snapback]</div>

PS My other driving nightmare is the guy not bothering to pass someone while driving in one of the left lanes of the freeway, plugging it up for all the rest of us!
[/b]

The dreaded "Parcheesi Block"

[chuck kershner]

I always drive with my headlines on (low beam in day) and my battery indicator is usually down about two bars in the blue. Occasionally I check to see if the indicator is green, so I must assume the engine is properly charging ... and use if properly discharging ... the battery as specified. To be sure, while driving a Prius is great fun, and seeing mileage in the 45-55 mpg range over wide terrain, one could easily become distracted looking at the displays and worrying, needlessly, whether one is getting the maximum effort out of the vehicle. My question always is: Am I getting maximum pleasure from driving this car and does it do for me what I expect - get me from Point A to B point efficiently, effectively, and and hopefully safely.

[patsparks]

The affect would be negligable.
One of those little green cars on the MFD fuel consumption screen repesents enough energy to run your headlights for about half an hour. Running your headlights would have such a tiny affect on fuel consumption that it doesn't justify thinking about.
If you think your headlights should be on, turn them on. If you are changing lanes or turning a corner, use your indicators. The fuel you might save is nothing especially compared to the cost to you and the environment if you have even a minor crash.
If you think your headlights are costing you fuel you should remove the radio and antenna, carpets, gloveboxes, centre consul, rear seats if they don't get used, air conditioning system, etc. All these things use fuel just by being in the car and more if you use the electric components

My personal rules for headlights are: -
If it isn't full daylight headlights on.
If the wipers are on so are the headlights.
If your journey is greater than 100km, headlights on.
If the car is moving you shouldn't have the parking lights on.
Fog lights stay OFF unless there is fog thick enough to affect vision.