LED tails vs Standard tails for gas mileage?

[DracoFelis]

Originally Posted by civic94

I see many cars with LED tailights, and most of them have about 15-20 led's on each brake light to replace 1 or 2 standard bulbs on each side. does the energy used in the LED's exceed the standard lightbulbs?

On those occasions when I've done LED conversions (from stock incandescent bulbs), I make a point of looking at the detailed specs of the replacement units I'm thinking of buying (IMHO if the place you are buying from is decent, they should have decent specs on the units, if not...). So looking up the power specs for the modules you are thinking of getting is probably the best (most accurate) approach here.

However, I've usually found that LEDs are significantly lower power than incandescent bulbs even if/when you have much more LEDs in the replacement module (in the latter case, it just means that many very low power light sources are replacing for a single much higher power light source).

And at least for brake lights, LEDs are also slightly safer (in addition to being lower power) due to the fact that they light up a fraction of a second faster when you press on the brake pedal (and therefore the car behind you has another fraction of a second warning about your braking, which at highway speeds can actually make a noticeable difference in reaction distance).

NOTE: I have most of my CRX switched over to LEDs (the exceptions are the headlights and some panel backlighting I can't easily reach), and the power savings does seem to make a noticeable (if not exactly huge) difference in my CRX's fuel economy. However, if you are doing this just for $$$ savings, I'm not sure how long the pay off is (as it may take quite a while to recoup the cost of your LED conversion in gas savings alone).

BTW: I've bought my car LED modules from http://www.superbrightleds.com . I'm not saying they are the best place, just the place I've purchased from in the past (so they are the place I have experience with). The main reasons I chose them was their nice (fairly complete) selection, and the fact that they post detailed specs on their modules on their web site (so I can make informed decisions to pick the module I think will work the best).

Oh, if you do go with LEDs, be sure to follow the advice on superbrightleds.com to match the LED color to the LENS color the LED is behind (i.e. use a red LED module for tail lights, not a white one even if/when the original bulb was white) for best results (brightest most crisp light). i.e. Don't make the mistake of going with a white LED module, simply because the bulb you replaced is white, or you will get dim washed out light. Only use a white LED module when you really want white light (for example, my CRX's white front-facing indicator/running lights call for a white LED module, but the brakes and tail lights call for red modules, and the turn lights call for amber modules).

NOTE: Another poster mentioned that you have to use loading resisters (essentially wasting any power savings from the LEDs) to use them as turn lights. That is one way to solve the problem of "incorrect load" on the turn lights causing them to flash at the wrong rate. However, another (power saving) option (in many vehicle models) is to replace the car's flasher with a unit that can properly flash with the lower current of LED modules (superbrightleds.com does sell replacement car flasher for some model cars). If you replace the flasher (and nothing else dealing with bulb load is present, for example a car computer that tries to warn of "burned out bulbs"), than you can generally use LED turn light modules WITHOUT having to add resisters to waste power!

NOTE: If you do want to start a LED replacement project, do look at the specs (paying attention to both power requirements and light output) when making purchasing decisions. From experience, I've found that it doesn't pay to get the cheapest LED modules available (that will fit the task), as frequently you get much better lighting out of some of the more expensive modules. In fact many cheaper modules will have noticeably less light than the stock bulb you are replacing (whereas some of the higher end modules produce more and crisper light than stock incandescent bulbs). So don't be cheap and buy modules that will produce noticeably inferior results to what you previously had. However, since sometimes newer LED module designs are both brighter and cheaper to make, sometimes the most expensive module is the wrong choice as well (so pay close attention to the module specs when purchasing).

[fowljesse]

Good info! I like that site, too.
I just let my turn signal flash fast. I couldn't find a law against it, and with LEDs, the on/ off is fast enough. I can't imagine that someone would mistake a fast flashing light for something else.
Another thing to note is which way the LEDs face. I have LED turn signal lights that point straight up from the base of the socket, and my housings are made for the light to come out in all directions (with the bulb coming in from the bottom), so I'm either going to put a dental mirror in at a 45 degree angle, or drill out the back of the housing, so the bulbs point the right way.

[Jay2TheRescue]

I had a vehicle fail the VA state safety inspection because the turn signal was flashing "too fast" I just replaced the flasher with a heavy duty flasher and didn't have a problem after that.

HD flashers flash at the normal rate, no matter what the load is on them.

[DracoFelis]

Originally Posted by Jay2TheRescue

I had a vehicle fail the VA state safety inspection because the turn signal was flashing "too fast" I just replaced the flasher with a heavy duty flasher and didn't have a problem after that.

HD flashers flash at the normal rate, no matter what the load is on them.

That's often true, but not always (so read the specs on the flasher before buying). Remember, the problem with LEDs is that you have less power needs than stock (which can cause incorrect flash rates and/or trigger "burned out bulb" sensors), whereas the "heavy duty flasher" is designed to work properly with more lighting/power needs than stock (as you get when you tow a trailer behind your vehicle).

So just because a flasher is "heavy duty" (designed to flash correctly even when you add lights from a trailer you are towing) doesn't necessarily mean it also flashes correctly on "light duty" (which is what you need for LEDs, due to their lower LED power requirements than stock bulbs). In many cases an HD flasher will work (since many HD flashers are really electronic flashers, with a constant flash rate across all loads they will work with), but not always. So if you are going with an HD flasher to fix LED turn light blink rates, it might be helpful to look at the flasher specs first (to make sure that particular flasher is "constant rate" even with the lower LED module load).

[Jay2TheRescue]

I was really pissed when they failed the van (2000 GMC 1 ton we use to go to flea markets) The inspector said that because it was flashing fast, something must be wrong. I specifically asked if any bulbs were burned out, he said no. Failed because it seemed "too fast". I bought a HD fasher and had no problems after that. I'm unsure if the flasher I purchased is electronic or not, as its just a big, black plastic cube. It was $20 so its possible.

[DracoFelis]

Originally Posted by Jay2TheRescue

The inspector said that because it was flashing fast, something must be wrong. I specifically asked if any bulbs were burned out, he said no. Failed because it seemed "too fast".

Interesting bit of trivia. My understanding (I think I read it on the web somewhere) is that the "too fast" flashing was done deliberately in most vehicals, as a cheap "burned out bulb" indicator.

Apparently some laws (at least in some parts of the country) called for new cars to show the driver when a turn bulb was burned out, and many car makers decided to meet that requirement by designing a flasher that flashes faster when under lower than stock current (thereby showing a "burned out bulb" by the fast flash). The fact that many car drivers were unaware of this "feature" seemed to be beside the point, the auto-makers had still technically met their "burned out bulb sensor" mandate by this "feature".

Of course, that's also why you need to swap the flasher when going to lower current LEDs, because if you don't the flash rate will be wrong even if/when you have all "bulbs" (led modules) installed. Just keep in mind that swapping the flasher like this will have the side-effect of disabling the "burned out bulb" indicator (i.e. the fast flash when a bulb is burned out). Since LEDs last so much longer than stock, this is probably a very minor point, but still something to keep in mind when doing a LED upgrade on a car.

Originally Posted by Jay2TheRescue

I bought a HD fasher and had no problems after that. I'm unsure if the flasher I purchased is electronic or not, as its just a big, black plastic cube. It was $20 so its possible.

If it worked for you, it probably was an electronic flasher (just not advertised as such). As I mentioned in a previous note, many so-called "heavy duty" flashers are really fully electronic modules with a constant flash rate.

But since a "heavy duty" flasher is designed to handle heaver than stock load, not the lighter than stock load of LEDs, it is something of a "crap shoot" if an HD flasher will work or not (because it depends upon how the maker of the flasher choose to design it to work).

[willix]

A conventional flasher is eletro/mechanical and noticeably clicks due to the moving parts contained with-in. As a digital flasher is silent and designed for the low current loads. A chime or buzzer is often included in the circuit to provide an audible indicator that a light is flashing. LEDs draw about 80-90% less load incandesent bulbs which is a big relief to the system.

[Jay2TheRescue]

The 1 ton van doesn't have any LED's installed, it is just a stock setup.

[theholycow]

Originally Posted by DracoFelis

Interesting bit of trivia. My understanding (I think I read it on the web somewhere) is that the "too fast" flashing was done deliberately in most vehicals, as a cheap "burned out bulb" indicator.

That is correct. I can't back it up with proof but I am certain of it.

It's effective enough...even if people don't know that it means that a bulb is burned out, it does at least give them reason to think something is wrong, at which point they would get the car checked. If they're willing to ignore that symptom then they probably don't care enough to replace bulbs anyway.

[DracoFelis]

Originally Posted by willix

LEDs draw about 80-90% less load incandesent bulbs which is a big relief to the system.

It varies with the exact LED module and bulb being replaced, but I think 90%+ (in extreme cases as high as 98%) is actually a closer estimate when you are talking about the smaller and/or colored bulbs that are common in cars.

The reason why LEDs do so well when matched against small incandescent bulbs, is that the smaller (i.e. lower wattage) the incandescent bulb is, the less light it will produce per watt of power put in. This effect is why you get approximately the same light from a 100 watt house (incandescent) bulb that you get from two 60 watt bulbs (even though the two 60 watt bulbs burn 20 watts more power). Since LEDs don't suffer from this effect (which plagues incandescent bulbs), percentage wise LED modules stack up better and better as bulb size goes down.

NOTE: The above talk about house lighting was mostly to illustrate the "small bulb problem" of old style incandescent lighting. However, my home is now mostly converted over to compact florescent bulbs (thereby saving a considerable amount on my home lighting bill).

As to colored light, incandescent bulbs can only indirectly produce it by throwing away (i.e. wasting) the light that is produced in colors other than the color you want. This can easily mean that the incandescent bulb has to throw away 30% - 90% (depending on the color chosen, and how "pure" of a reproduction of that color you need) of the light produced to get the colored light you desire/need. Again, LEDs excel here, because you can design LEDs to directly produce the color of light you desire instead of having to throw away light to get the colored light indirectly (as is necessary to do with incandescent bulbs).

For example, I seem to recall my stock license plate bulbs (two of them), were rated at 5 watts each per bulb, however I just looked up the specs on my 5-LED white LED module replacements as using only 26mA @ 12volts (aprox 1/3 watt per LED module). And that's for the less efficient (for LED modules) white light, not the colored light that LEDs really excel at.

So just by replacing the two license plate lights saves me a little over 9 watts (around 2/3 of an amp, if we assume my alternator puts out about 14.5v to my car's electrical system) whenever the license plate lights are on (which includes any time my main lights, or just my running lights, are on). And that's just the power savings from upgrading the license plate lights.

When you add up the savings from all the misc car lights (being converted over to more energy efficient LEDs), it can easily total a few amps of electrical load on the car's alternator. Now a few amps difference in electrical load won't translate into a huge difference in fuel economy, but at least on some (smaller) cars (such as my CRX) it is enough of a load difference to be noticeable at the pump.