Question related to wire thickness

[moses123]

Hello,
I was wondering how to reduce the wire thickness in auto headlight system.
I am using 2 of 100W bulbs, 12V battery and 2.5mm² wire of 2 meters.

I want to use 1.5mm² wire instead of 2.5mm²... I saw in many cars 1.5mm² wire is used but i cannot figure it out how they do it to control wire heating and damaging...

It would be great if anyone can help me in that...

Thank You!

 

[4pyros]

You should not reduce the wire thickness in an auto headlight system.

There are many factors to consider in selecting a safe and piratical wire size.

Will one wire carry the full load of one or two lights.
What is the melting point of the wires insulationshoin.
How the wire is run to dissipate heat.
How much voltage drop is in the wire and how much less light you will get from your headlights.

No matter what a smaller wire will drop more voltage meaning less light.

 

[MrAl]

Hello,
I was wondering how to reduce the wire thickness in auto headlight system.
I am using 2 of 100W bulbs, 12V battery and 2.5mm² wire of 2 meters.

I want to use 1.5mm² wire instead of 2.5mm²... I saw in many cars 1.5mm² wire is used but i cannot figure it out how they do it to control wire heating and damaging...

It would be great if anyone can help me in that...

Thank You!

Hi,

I am not exactly sure what you are doing there so i'll just provide some general information.

If you are running two bulbs with wire that has cross sectional area A, then you can run one bulb with a wire that has cross sectional area A/2. This means if you drive each bulb individually you can use a smaller wire.

Shorter runs of wire can use smaller wire. Number 14 gauge wire is a standard for 15 amps, but over shorter runs you might get away with 16 gauge, and you might be able to squeeze 17 amps out of it for a short run. What you should do is test it and see if it gets hot.
You also need to check for voltage drop. If the voltage drop is too high you'll loose power getting to the bulb(s) and that makes them quite a bit dimmer.

There's no way to make a wire that is already getting hot get cooler without some means of cooling such as fans.

Also, the wire insulation has something to do with it too. If the wire insulation of one wire is rated at a higher temperature than another wire, that wire will be able to pass more current before it starts to melt the insulation.

If you really need to use smaller wire then perhaps you can run each bulb separately, or even just parallel two sections of the thinner wire and drive them both. Two wires that each have area A make a wire that has area 2*A which can handle about twice the current.

 

[JimB]

On a slightly different tack, there is thin wall cable.
Look here:

https://www.autoelectricsupplies.co.uk/product/70/category/114

The PVC insulation is harder and thinner than standard wire, giving a smaller overall diameter to the wire.

JimB

 

[unclejed613]

also wire with teflon insulation is often rated at over twice the current of wire with PVC insulation of the same wire gauge, because of the higher melting point of the teflon. the resistance and voltage drop across the wire remains the same, however, and the wire does get hot. also the fusing current of the wire remains the same, because the melting point of the copper is the limiting factor.

 

[ChrisP58]

Do all headlights draw the same current?

That could be a reason some cars have smaller wires. If the lamp has a lower power rating either due to being smaller, or is of a more efficient type.

Anyone making LED head lamps yet?

 

[dr pepper]

In the uk for filament lamps most cars are 55w dip and 60w main beam.
Dont know about gas discharge, they seem to be trendy.
I made a 10w led front light for my pushbike, its excellent and you can get 50's and 100's so the technology is around for led headlights, but I dont know if a manufacturer is fitting them yet, maybe they are still waiting to be approved by the mot.

 

[WTP Pepper]

I beleive there was an old By-Law introduced in the UK to only allow incandescent lamps it be used in car headlights. I think it was to prevent using wax candles as LEDs weren't around then. Sorry no source.