Could LED lights improve MPG?

[rstrohkirch]

It absolutely matters how much light a system outputs

It only matters in a system you can control.

In order to draw a holistic conclusion one must make a comparison between two systems of equal output/performance.

We are talking about fixed systems here. You used information from an article that details the differences between an OEM system to support your conclusion on power draw. This means that we not modifying or altering these system with aftermarket or other solutions. Because of this the output does not matter and we are limited to real world examples of what the OEM of the vehicle you choose makes available to you.

You made your point earlier on what you would gain by lowering system draw by 55w and answered the OP. There wasn't anything wrong with your math. But then you guys get into about what system is the most efficient when you can't even control the system to begin with. We know that LED and HID offer an efficiency advantage over halogen. The next step to the conversation should be trying to determine what kind of current draw common offerings from OEMs for all 3 systems actually are. Finally, I think it's fairly safe to assume that the total lumen output between a vehicle that offers HID or LED options isn't going to 10x different.


Example:

OEM gives you halogen or LED option. They use a 55w halogen bulb or a 50w LED on the low beams. They gave you more lumens but you saved almost no power.

 

[JCH13]

Your point is made. The continuation of the conversation was to push agent00f to supply some sort of information or source for the claims they make. This is something agent00f has done a few times now - make a wild claim with nothing to substantiate it.

Perhaps it is partly my fault for continuing the conversation after agent failed to provide any information to prove their assertions.

 

[jdoggg12]

My $0.02...

You'll do better for mpg by going 0.25 mph less than usual on the freeway than using lower (or even near-zero) wattage bulbs.

 

[Yuriman]

My $0.02...

You'll do better for mpg by going 0.25 mph less than usual on the freeway than using lower (or even near-zero) wattage bulbs.

Completely true, adjusting the nut behind the wheel is easily the best way to gain economy. In my case, I do all of the above. 1600 ways to save an ounce, so to speak.

 

[evident]

You could offset that efficiency saved from alternator by replacing the alternator brush pack...

 

[desura]

I'm kinda surprised no one has come up with a car solar system which trickle charges the 12v battery. Not only do you get a slight efficiency bump, but also you have fewer situations where you have a dead battery you have to deal with. LED lights fit in there as well. Lower power draw likely means less wear on the battery itself, less replacement needed, and more security that you won't go out to a dead battery.

 

[JCH13]

Solar cells on car roofs have been evaluated to no end and have not been implemented because it does not make sense to do so. They are woefully inefficient because the car roof does not tilt to match them against the incident angle of the sun.

 

[desura]

So from the looks of it, LED lights actually don't have much of an efficiency advantage if at all. Most of the bulbs on amazon tout brightness as the draw, but I'm simply looking for long-lasting efficiency. It looks like both LED and HID lights can be had at 35watt, below that really nothing for either. LED also has a heat problem?

 

[agent00f]

So, no sources to suggest that 30L/W is unreasonable.

It is true that HID isn't the best for brights. Maybe Audi compared 70W of HID lows and 70W of Halogen brights. *shrug*

Not sure why you went off on a tangent with reflectors...

A claim of 75% loss is completely comical except to folks eager to believe whatever they found on the internet. It's similarly hilarious when someone who has no idea that LED also need optics, or they are typically less efficient than HID ones is positing that the latter is the cause of this, or figure why it's irrelevant even after an explanation. Or desperately grabbing whatever goalposts they can find about high beams after it was revealed they don't even know the wattage of the bulbs, or how high beams work, or anything really.

 

[agent00f]

It only matters in a system you can control.



We are talking about fixed systems here. You used information from an article that details the differences between an OEM system to support your conclusion on power draw. This means that we not modifying or altering these system with aftermarket or other solutions. Because of this the output does not matter and we are limited to real world examples of what the OEM of the vehicle you choose makes available to you.

You made your point earlier on what you would gain by lowering system draw by 55w and answered the OP. There wasn't anything wrong with your math. But then you guys get into about what system is the most efficient when you can't even control the system to begin with. We know that LED and HID offer an efficiency advantage over halogen. The next step to the conversation should be trying to determine what kind of current draw common offerings from OEMs for all 3 systems actually are. Finally, I think it's fairly safe to assume that the total lumen output between a vehicle that offers HID or LED options isn't going to 10x different.


Example:

OEM gives you halogen or LED option. They use a 55w halogen bulb or a 50w LED on the low beams. They gave you more lumens but you saved almost no power.

Halogens are 55w, HIDs are 35w and LEDs are similar. Perceived brightness scales as 2-3 inverse polynomial of output so HID/LED aren't really about lumens per se but quality of the beam. With either a sharper point source or better defined emitter surface boundaries you can control the beam better and thereby illuminate what needs lighting, for example signs on the right side of the road.

Your point is made. The continuation of the conversation was to push agent00f to supply some sort of information or source for the claims they make. This is something agent00f has done a few times now - make a wild claim with nothing to substantiate it.

Perhaps it is partly my fault for continuing the conversation after agent failed to provide any information to prove their assertions.

It's not really my fault some people place more faith in links from others at their level plus motivated reasoning than those who actually know what they're talking about.

 

[jlee]

A claim of 75% loss is completely comical except to folks eager to believe whatever they found on the internet. It's similarly hilarious when someone who has no idea that LED also need optics, or they are typically less efficient than HID ones is positing that the latter is the cause of this, or figure why it's irrelevant even after an explanation. Or desperately grabbing whatever goalposts they can find about high beams after it was revealed they don't even know the wattage of the bulbs, or how high beams work, or anything really.

https://yourlogicalfallacyis.com/ad-hominem

 

[agent00f]

https://yourlogicalfallacyis.com/ad-hominem

It's an entirely rational argument that someone who can't do arithmetic can't derive correct algebra. Ponder that for a while and ask questions if still too confusing.

 

[Yuriman]

Getting a bit off topic.

For what it's worth, I went with a proper protector / 35w HID retrofit, as I feel aftermarket LED solutions aren't mature enough and offer less value. I expect they'll take over eventually but they're certainly diminishing returns over HID.

I also replaced all of the exterior and interior halogen bulbs with LEDs. At night (only) I probably save about 100w total, which is roughly 1/7 of a horsepower (yes, you can compare them this way because they're both measures of power) before conversion loss, which is very low since I drive a hybrid. Even after DC-DC conversion, you're still looking at upper 80's.

 

[JCH13]

Agent00f, you haven't provided any sources or information to show that you 'know what you're talking about,' nor have you demonstrated that anything that I posted was incorrect or misleading, especially not any of the math I presented.

 

[evident]

Getting a bit off topic.

For what it's worth, I went with a proper protector / 35w HID retrofit, as I feel aftermarket LED solutions aren't mature enough and offer less value. I expect they'll take over eventually but they're certainly diminishing returns over HID.

I also replaced all of the exterior and interior halogen bulbs with LEDs. At night (only) I probably save about 100w total, which is roughly 1/7 of a horsepower (yes, you can compare them this way because they're both measures of power) before conversion loss, which is very low since I drive a hybrid. Even after DC-DC conversion, you're still looking at upper 80's.

I completely agree that LED systems for headlights aren't there yet. My RX350's HID output better light than many of the newer vehicles' LED headlights at the moment. i think it's getting much closer though. and I love retrofitting vehicles w/ HID systems. such an awesome, substantial upgrade on an older vehicle.

 

[agent00f]

Agent00f, you haven't provided any sources or information to show that you 'know what you're talking about,' nor have you demonstrated that anything that I posted was incorrect or misleading, especially not any of the math I presented.

I've said all that needed to be on someone who insists on believing some site that includes electronic ballast or whatever else in their supposed 75% optical loss.

 

[JCH13]

I insist upon nothing more than data-driven conclusions. But since any burden of proof is too heavy of a lift for someone as smart and as important as you, I guess that I'll just be on my way.

 

[agent00f]

I insist upon nothing more than data-driven conclusions. But since any burden of proof is too heavy of a lift for someone as smart and as important as you, I guess that I'll just be on my way.

Google allows even less than smart people to look up reflector/lens losses mentioned. Hint: it's a lot less than 75%.

As for a practical comparison: https://www.youtube.com/watch?v=_HWvISAcP7Q, note the similar frontal area.

 

[JCH13]

The initial source I linked noted 40% reflector loss. Not 75%. Additional losses come from temperature-related inefficiencies (and HIDs do get warm) and power supply/ballast losses. Both LED and HID suffer from losses due to the headlight lens.

Note that HIDs had a TOTAL SYSTEM efficiency of about 25%, and the LED was about 50%, which more than makes up for the LED source efficiency deficiency.

 

[agent00f]

The initial source I linked noted 40% reflector loss. Not 75%. Additional losses come from temperature-related inefficiencies (and HIDs do get warm) and power supply/ballast losses. Both LED and HID suffer from losses due to the headlight lens.

Note that HIDs had a TOTAL SYSTEM efficiency of about 25%, and the LED was about 50%, which more than makes up for the LED source efficiency deficiency.

" Typically, 40% or more of the light emitted from the lamp is trapped within the luminaire and does not reach the target area."


"Tobacco company proclaims smoking not harmful". HIDs are typically surrounded by a reflector and have a simple two surface lens up front, a typical halogen reflector doesn't even have a lens. So where exactly is that extra 40+% magically going except what motivated dummies are willing to swallow?

 

[JCH13]

I have yet to see any evidence that contradicts the 40% number. You saying it over and over does not count as evidence, despite what you seem to believe.

 

[agent00f]

I have yet to see any evidence that contradicts the 40% number. You saying it over and over does not count as evidence, despite what you seem to believe.

"In lieu of any evident that contradicts my self-interest to believe in pink unicorns I can only persist no matter how comically stupid".

Have you even ever seen a headlight, or what they call "Traditional lamps"? This is what they look like by the way:

http://what-when-how.com/automobile/headlight-automobile/
or

 

[natto fire]

No

I am going with this answer. It is actually comical to me that this thread has gotten so technical, and that many posters here hate hybrids or BEVs.

The wasted energy from keeping an ICE idling during an average commute makes this whole point irrelevant. A gallon of gasoline contains a large amount of energy, which makes translating watts to the MPG crowd almost impossible.

 

[jlee]

You saying it over and over does not count as evidence, despite what you seem to believe.

Heh. It's somewhat amusing watching a consistent appeal to authority where the authority in question is also the person making the claim.

Still waiting for a source from agent...

 

[desura]

So I'm thinking now of replacing my headlights for my Ford C-max. Aside from the efficiency thing, I can barely see them while on the road much of the time.

Recommend some HID lights? What color temperature is best?