Daylight Driving lights & Fuel Economy

[CelticLhad]

Hi guys,

This query kinda relates to any thread about daylight lights...

http://briskoda.net/octavia-ii/led-daydriving-lights-octavia-ii-rs/123443/#post1441294

Anyways, i was listening to a radio2 programme about MEPs wanting us all to use daytime driving lights by 2012. As usual they did the usual of presenting both sides of the coin but the bit that got me was that driving with lights on during the day would cost £160 in fuel!

Now i thought that the lights were free cos they worked off the battery!? Can anyone help explain this as i also quite often have my lamps on during the day on motorways?

Cheers The 'Lhad

[PumpeDuse]

You get nothing for free in this life. What charges the battery?.................answer the alternator, how is the alternator driven, via the engine, when the alternator is charging it puts more strain on the engine, the engine has to work harder, hence using more fuel. As a test, sit at idle, note the rpm, then turn on the heated rear windscreen and watch the revs fall a little. :-)

[sms]

the battery is like a water tank in the loft, but running off it is lots of pipes to various bits of the house (bathroom, kitchen, bathroom, toilet etc) , everytime something is operated e.g. toilet it takes the water from the big tank and the big tank needs to be topped back up again by the mains pipe from outside (this on the car would be the alternator). so the water is pumped back to the top of the house it needs a motor (in this case the car engine) which in this case has got to work harder as not only is it trying to run the car its now got to do a second job at the same time (running the alternator harder) to top all this up.

Its an explaination my dad gave me many years ago and makes things easier for those trying to understand things like that

[gilesme]

I think the costings were done on "old fashioned" filament bulbs - Audi etc. are putting in LED running lamps which use a fraction of the leccy (i.e. a very thin water pipe...), so shoul dbe a lot cheaper to run.

[cheezemonkhai]

I was going to say that if you used LED's instead then you are talking of going from maybe 55w if they calculated dipped beam or 5W on sidelights, to 2W of LED.

[skippy41]

Are LED headlight bulbs available yet,??? and could someone suggest where the cheapest place to get the ones for the rest of the retrofit replacements for the OCTY, IE side lights indicators and so on, and are they a strait swap??

[Obadiah]

Having only just got the Octy, I haven't looked at things like bulbs yet, so don't know if they match our 'standard' bulbs, but I have a link from another car forum.

Automotive Led Bulbs - by Ultra Leds U.K

[sms]

a guy with a fabia at the briskoda/trax event had some on his fabia, that stick around the light casing and is that thin that doesnt get in the way. surely wire this straight to the side light wires and you have daylight running lights (they looked bright enough) but using less power.

[vRS Carl]

you cant use LED bulbs in the MK2 Octavia as it gives you a bulb failure warning light on the Dash

HTH

Carl:thumbup:

[Sammycarp]

you cant use LED bulbs in the MK2 Octavia as it gives you a bulb failure warning light on the Dash

HTH

Carl:thumbup:

Surely you could incorporate some sort of resistor in the circuit, as they do with LED indicators? Would that work the same way?

[Captain Sisko]

But what happens if an LED fails? are they easy to change? or will garages see this as change the the whole unit time with a labour intensive charge?

But seeing as some cars have bulbs which are quite inaccessible then having long lasting LED lights means no more fiddling about with clips in tight places

[skippy41]

Please could we have a list of what MK2 bulbs can at the moment be swapped over to LED and where to obtain them

[vRS Carl]

Please could we have a list of what MK2 bulbs can at the moment be swapped over to LED and where to obtain them

None apart from the interior lights for when the doors open.

Ive tried indicator/brake bulbs etc and they all gave Bulb failure warnings (even with resistors) so until someone comes up with a bulb that includes the resistor inside that will fool the ECU im afraid you cant

Carl:thumbup:

[skippy41]

None apart from the interior lights for when the doors open.

Ive tried indicator/brake bulbs etc and they all gave Bulb failure warnings (even with resistors) so until someone comes up with a bulb that includes the resistor inside that will fool the ECU im afraid you cant

Carl:thumbup:

Do these interior ones give off more light and what size do you require??

Could you have the bulb fail indicator turned off

[chavdarlk]

Ive tried indicator/brake bulbs etc and they all gave Bulb failure warnings (even with resistors) so until someone comes up with a bulb that includes the resistor inside that will fool the ECU im afraid you cant

Carl:thumbup:

Do you know, that the resistor have to be installed in parallel with the LED lamp?

If you do it this way, it should work fine!

This is table with common power to resistor values.

The formula itself is R = 160 / P.

 1W = 160 ohm
2W =  81 ohm
3W =  56 ohm
4W =  39 ohm
5W =  33 ohm
7W =  24 ohm
10W =  16 ohm

For example, if you want to use 3W LED lamp in place of 10W traditional bulb, you have to install in parallel 24 ohm / 10W.

Take care with power rating of resistors!

[Oli]

Has anyone done any calcs or real world tests anywhere in the world that would relate ampage draw to fuel consumption?

[sebulbus]

You can fake it with a capacitor. A resistor would become immensely hot due to the current passing through it, potentially melting through the entire headlamp housing. I'll get back with the exact figures.

[gilesme]

Having only O level physics... if you stick a resistor / capacitor in, will the current drain be the same as a normal filament bulb ?

[sebulbus]

It will be close to the same, but not necessarily there. The blown bulb feature wants to see a significant current draw, else it will trigger.

[sms]

unless there is an option on vag com to switch off bulb warning feature. i personally as i posted above would keep the side bulbs in and wire off it some strip led's which you have stuck to the housing of your lights. they about 2mm thick so dont take up much room.

[chavdarlk]

You can fake it with a capacitor. A resistor would become immensely hot due to the current passing through it, potentially melting through the entire headlamp housing. I'll get back with the exact figures.

This would work only if computer senses the current only in the very first moments of switching the light on.

Anyone tried to remove a bulb while lighting? Is there an indication in this scenario?

[richardjh]

i leave my headlights on all the time. I have a dark grey car and think it is better to be more visible. running a few tens of watts of electical load is negligable in the overall power consumption from the engine.