LED Lights

[Zerohour]

So now that we're into winter, I'm driving with my lights on pretty much my entire commute.

I'm looking into getting some LED bulbs, but I'm trying to debate the cost of purchasing them....I see rear bulbs ranging from $8-$30 dollars, not to mention the special flashers to use LEDs at the proper blink rate. I'm looking at easily breaking $100 to save 100W's. I'm just not sure its worth it.

I thought about maybe building sets of them, but for the time spend doing so and hacking apart a extra set of headlights, the cost is going to be the same ($$$).

I was just wondering if a few other eco-modders can chime in on their experiences. Please include what bulbs you replaced, where you got them, approx. costs, and any +/- feedback about the bulbs.

[gone-ot]

...if you keep cars for a LONG time, it's probably worth the effort; but if not, then you probably won't recover the co$t inve$tment.

...some of the newer white LEDs are getting MUCH more powerful, almost laser-ligke in output (and current draw, too, of course).

[RobertSmalls]

I submit that it would take 25000mi of nighttime driving for each 6.7W #3157 taillight bulb to burn a gallon of gas at 50% alternator efficiency and 25% ICE cycle efficiency.

Will the bulb pay for itself? Eh, maybe a wash if you're lucky.

The big pros and cons of LED taillights for me are the quantity, intensity, and directionality of their light.

[Zerohour]

I'm trying to figure out how much draw the LEDs actually have on some of these bulbs. its hard because the rating is not given.

A normal 5mm LED is generally 20-30ma. the large 10mm are up to 50ma. So if the "superbrights" are the 50ma type, a 20 LED-bulb goes to 1amp @ 12 volts which is 12 watts...the current 3175 bulbs are 8watts. So some of these could actually be increase electrical consumption!

I'll spill a few more details as to why I'm interested:

My subaru has FOUR 3175 bulbs @ 8W (without braking) plus the two plate lights @ 5W a piece. When I hit the brakes the wattage goes up to 27 on two of the 3175 bulbs. this is not including the third brake light. Quite seriously if I have blinker and and use the brakes (common to slow while turning) the load put on the car is near 100W from brake lights and blinkers. This would include times while sitting at traffic lights. When I'm in traffic in the morning during cold commute this actually causes the low beams to dim and the idle to creep up. Part of the reason I would like to swap to the LEDs as I hit ~10 stops on the commuting path. I probably spending up wards of 8 minutes daily sitting idle with the a 100w load on the alternator at idle.

[sid]

LEDs drop anywhere between 1.4 Vdc to 4.5 Vdc per LED, depending upon the color and construction. Most red LEDs drop about 1.5 Vdc, though I don't know if this is still true for the super bright ones. So multiple LEDs are often wired in series and share the same current, which saves considerable power. The sum of the voltage drops of all the LEDs in series must be less than the source power, which is about 12 Vdc for most all automobiles, with the difference between the drop across the LEDs and the source power being dropped by a resistor or a regulator circuit.

[Zerohour]

Good call Sid, I was thinking of a basic one led + resistor circuit for a 12volt automotive application!

A 3v * 0.05ma would only be 0.15 watts, so the 20 LED bulbs would be 3 watts. And those are the dual circuit bulbs which function as brake lights. So the steady on position should be ~half or 1.5W, which is a 6.5 W drop across 4 bulbs. Savings of 26 watts/~2.2amps.

If I swap off the dual 5w plate lights to single led it would go down ~9 watts. Not sure if these would be bright enough, but i have some white LEDS and holders laying around.

The third brake light is a 18w 921 bulb, which I found a 6-3mm Led bulb that is a replacement. 0.020a * 3 volt = 0.06w, @ 6 leds + resistors round 0.5w compared to the 18w currently in place. ~17 watts saved

So looking at 26+9+17 = 52watts or 4.3amps. For the 90amp alt in the Subaru thats ~5% load just from the rear tail lights. Its obviously enough to make the idle change at cold morning runs, so I'm wondering if the minor gains would be worth it?

Not sure if that is worth the bulbs

[Zerohour]

Found a site that gives the specs on the units:
Third brake light........0.051 amps (x1)...........vs....1.5 amps (x1)
Brake lights..............0.018/0.053 amps (x4) ..vs....0.666/2.25 amps (x4)
Plate Lights..............0.026 (x2) ..................vs....0.416 amps (x2)
Park/Corner Lights.....0.088 (x2) ..................vs....0.666 amps (x2)

Total.......................0.351................. .......vs...6.328

So six amp difference...hmm

6 amp x 12 volt = 72 watts
72 / 745.7 = ~0.10 hp (0.0965)

[endurance]

I'm considering the LED mod just for the sake of being able to do a bit more EOC with lights on and being able to leave my parking lights on while stopped at stop lights without worrying about the drain on my battery. I don't see them being cost effective any other way, but if I can have my engine off for 15 minutes a day (total 1.4-1.5 hour commute time), at .25 gallons per hour, that's a savings of 15 gallons a year... in theory.

While I haven't ordered the car bulbs from deal extreme, I've placed dozens of other orders with them over the last three years on various project builds (LED lights for 24 hour MTB racing). Right now I'm waiting exceedingly long (3 weeks) because international shipping is at a standstill because of the Al Queda package bombing threat, so just be aware before you order. Otherwise, shipping is $0.01 no matter how big or small your order, which probably makes their prices better than anywhere else you'll find.

My big issue is headlights. While HID may offer better performance and a tad bit of energy savings, LED would be the way to go. I'm likely to custom build something at some point because I can easily make a pair of 900 lumen LED lamps that consume 20w vs. 70w+ for a pair of halogens. I'd also have the option of building a low/mid/high beam configuration that could accommodate my needs, whether in city traffic, where I merely need to let my presence be known vs. being able to travel on highways with wildlife. The challenge remains fitting them in a housing that still allows you to bleed excess heat and focus/beam patterning. That's why I need to start with a set of lights from a junkyard, so I can experiment without risk of screwing up my one way of getting to work.

[Zerohour]

Well I'm not looking at the headlights (not yet). I'm just looking at the standard load from having the lights on. And its not even so much of getting a pay back out of the bulbs. Its more of how much MPG can I get. lol If the 0.1hp gave me .01 gallon less all the time during winter it would be awesome. but I'm pretty sure its much less. But the lights are still something i'm considering. I'm still looking for maybe someone who has more experience with electrical savings on the alternator. Rotational mass is always spinning so its not like I'm going to get a % increase from removing the alt all together. But they respond to electrical load. One which could be a of mild benefit.

The Subaru also has a special little feature (what I consider a mental spasm of a design). The day time running lights are the H1 headlights powered on the low beam @ 35W instead of the 55W. So at night given good conditions I swap down other parking lights and roll with the day time running lights. In well lit locations like in town, highways, traffic, the 20W per side is a waste. So for now I'm not after headlights, just all the other bulbs that I use all the time in the winter months.

[ecofreak]

If you ran an older diesel, you might want to switch out LEDs and glowplugs for battery efficiency. I'd rip out the stereo and AC if I was going for battery efficiency.

If you have an older bike light run by a dynamo, you could replace the dynamo with a 9V battery and swap the lightbulb for a few LEDs.