Experiment: The cost of Headlights

[04_Sentra]

Originally Posted by Angelus359

Use LED headlights?

I actually said LED lights. One could start with taillights. LED headlight mod would be an insignificant effort compared to some of the other mods that have been covered on this site (engine swaps, etc.)

[frankspinz]

You can buy LED light strips (fairly cheap) that could be used in place of daytime running lights. They are more and more common on new car models. In states & provinces where DRLs are mandatory - since they are on all the time, it might be worthwile...

[brucey]

My car originally had DRL's. I disconnected them because I hated going to the drive in theater and having nanny state tell me it was time to blind everyone there.

[Zerohour]

Brucey, nice write up. A few weeks back I posted up about swapping LED lights into all the of the bulbs that are non-blinker. The cost was ~$60 and totaled near 72 watts of power demand dropped. Since we have near identical cars and electrical setups, I would wonder if I could get ~1/2 mpg doing the swap.

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)

I am wondering, how did you disable the DRL? They turn off with the ebrake and I thought about putting a trip switch in that circuit to turn them off. Is there a better way?

[brucey]

You simply unplug the white connector under the dash.

Pictures here: DIY: Disabling DRL (2000-2004) - Subaru Outback - Subaru Outback Forums

I used to also pull the ebrake up to disable them, but once I adjusted my ebrake properly I didn't want to grind into the brake to turn them off. Plus the brake light coming on was annoying.

Also. 60$ for .5 MPG isn't too bad. It's a shame it's only at night, or I'd jump right on it. Although, with just 70 watts saved it'd probably be more like .25 mpg. Which is a bit harder to swallow. I actually have interior and license plate LED's but only because they burned out on me and I didn't feel like changing them ever again.

[ConnClark]

Actually a cars battery and electrical system is about 13V to 14V. So 6 amps is about 80 Watts. Also factoring in alternator efficiency should be done.

80/745.7 = 0.11 (0.10728)

0.10728/ .7 = 0.153 HP

In reality it would be more HP than this because I used a very high value for alternator efficiency.

[Zerohour]

yeah some quick math goes a .5mpg gain -> $0.0022 per mile. Cost of $65 yields a pay back after ~30,000 miles.

I wonder if the LED bulbs have any sort of black friday / cyber monday sales? lol

[Frank Lee]

I really don't think the brake and 3rd brake lights should be included in the estimate. They are on, what, .001% of the time?

[brucey]

For hypermilers yes. But you should see some people drive around here. Brake ALLLLLLLL the way down the mountain. Brake randomly on the highway. Brake to take a turn. Brake to put there blinker on...

Although, 30k Payback isn't THAT bad.

[Zerohour]

Subaru's use a dual circuit bulb, so yes they are on all the time if the headlights are on. The values given are the values at the 8watt circuit and not the 27watt circuit for brakes on. When sitting at lights the electrical consumption would peak up to ~125watts instead of the 70 or so saved. I did not include the stoplight function in the values, only the steady-state on position.