Effects of Headlights on mpg: 6%?

[COcyclist]

On North American VWs the headlights are Daytime Running Lights at 70% power. I disabled the DRLs and installed a "Euroswitch" which gives me parking or city lights (depending which side of the pond you are on). I used two yellow LED marker lights in the grill wired into a switched fuse tap for DRLs. I like the safety aspect of the yellow LED marker lights with minimal draw on the alternator. They should last the life of the car unlike the headlight bulbs you always see burned out on VWs in this country.

[redpoint5]

Originally Posted by RobertSmalls

The corner lights and dash lights draw about 90W, and headlights draw 110W according to my own measurements. For a 50% efficient alternator, that's an additional 400W (0.5HP) at the crank...

Thank you for this practical analysis.

My car has HID bulbs, which consume 35W/bulb compared to the typical 55W/bulb incandescent. That means I'm drawing 40% less electrical power. Not only does it draw less energy, it puts out 3x the light. People who appreciate FE would also appreciate electrical efficiency.

[gone-ot]

Originally Posted by redpoint5

People who appreciate FE would also appreciate electrical efficiency.

...efficiency is efficiency, regardless of whether it's mechanical (engine) or electrical (motor).

...using LESS is the goal, wasting LESS is a merely a reciprocal!

[Peter7307]

Originally Posted by Arragonis

I have xenon headlights and like others run with them on full time except in sunny weather as only the blind it seems are allowed to drive in Edinburgh

Not often you see Edinburgh and "sunny weather" in the same post !


More usefully...information from Holden (A local subsidiary of GM) states a difference of about 2% for lights on vs lights off.

The actual number varies depending on engine size , average mpg , weather etc.

This was in response to a suggestion of using daytime "running lights" as some places in Europe currently mandate.
Never went anywhere by the way.
This isn't Stockholm after all and blizzards are not all THAT common in Sydney .
Peter.

[Vekke]

More interesting data here: https://www.sciencedirect.com/scienc...60128516300442

[SDMCF]

Originally Posted by Vekke

More interesting data here: https://www.sciencedirect.com/scienc...60128516300442

That is a fantastic document with information about how many factors impact fuel consumption. Well worth saving and studying. Thanks for posting that.

Whilst headlights have to be on all the time when outside towns in Finland, I did accidentally drive to my office (119 Km) recently without them. The best consumption I normally get on that trip is 4.0 L/100 Km (58.8 U.S. MPG) but without headlights my consumption was 3.8 L/100 Km (61.9 U.S. MPG) so 5% reduction. After that I read up on alternator delete options on this site. I have put together a contraption using a secondary battery and a boost converter to create a virtual alternator delete solution. So far I have only used it on a couple of shorter journeys and have no meaningful test results. I will try it on occasional office trips over the next few weeks and hope to get some better data.

[Logic]

A company called Valeo seems to have an "up to" 80% efficient alternator line for sale.
The difference seems to be in the use of Mosfets rather than diodes during rectification.
If that's all they changed (really!?); modding your current alternator to do likewise may be an option..?

Valeo Innovative EG Efficiency Alternator Wins A 2015 Automotive News PACE Award
The EG Efficiency Alternator features synchronous rectifying based on MOSFET (Metal Oxide Semiconductor Field Effect Transistors) instead of diodes. Due to their micro-electronic structure, MOSFET’s are able to almost eliminate the voltage drop during current rectifying. The alternator’s efficiency is increased by 10 percent.
https://www.valeo.com/en/valeo-innov...ws-pace-award/

How Does The Valeo High Efficiency Alternator Work?
https://www.valeoservice.com/en-com/...lternator-work


Up to 80%...
https://www.valeo.com/en/catalogue/pts/12v-alternator/

IMHO using an adjustable vacuum switch to turn of the rotor field winding most of the time so the alternator only puts load on the engine/charges during overrun/ braking should be a std feature.
ie: Charge with 'free' energy (momentum) only.
(Requires gearing down while slowing/braking)

Obviously there's circuitry to override this should the battery be too flat.

You can adjust the vacuum switch so it's charging during low load cruise too, or any setting of your liking in between.

There's a lot of discussion on this and using the same simple circuit on the aircon pump clutch, etc, elsewhere here.

[Ecky]

Mazda already has extra alternator loading during braking. They introduced it on many models sometime shortly after 2010. They also opted to put supercapacitors in their cars so that extra current didn't just boil the batteries or get wasted as heat (because at max current, it was considerably more than a 12v battery could absorb).