Why do auxiliary lights need a relay?

[teriyakimonkey]

If I used thick enough cable and a good enough switch and fuse holder coming directly from the battery, would I still need to fit a relay?

[off-the-planet]

No, but the lights would be controlled only by your switch, not by the ignition key or any other lighting switch. This could cause you problems if you forgot to turn them off when you parked the bike, (or some wag turned them on whilst it was parked), ie you'd come back to a flat battery!

[teriyakimonkey]

Very good point! DUH!

Thread finished due to dumbarse question.

[bazza]

fitted mine with a inline fuse only and never had a problem , however no pratts turned them on for me yet . never thought about that.

[jasonbc]

If I used thick enough cable and a good enough switch and fuse holder coming directly from the battery, would I still need to fit a relay?

depends on the amperage they draw. a relay has a small coil in it which takes a small voltage and then effectivly can amplify it and just use 1 or 2 pairs of contacts to output the voltage to another aplliance

[Tarka]

The auxiliary lights must only be able to come on with the bike`s lights selected...'fogs' with low beam and 'spots' with high beam.

Therefore you use the high beam or low beam circuit on the bike to switch the relevent relay coil.

The relay contacts carry a seperate fused feed from the battery to the auxiliary lights.

It also saves the delicate and low current rated handlebar switchgear contacts from arcing or pitting due to the extra current loading.

[Tarka]

depends on the amperage they draw. a relay has a small coil in it which takes a small voltage and then effectivly can amplify it and just use 1 or 2 pairs of contacts to output the voltage to another aplliance

Oh dear...I know you mean well...

The relay coil takes a smaller CURRENT or AMPERAGE but the same VOLTAGE as the lamps.

[XR Mad]

Oh dear...I know you mean well...

The relay coil takes a smaller CURRENT or AMPERAGE but the same VOLTAGE as the lamps.

Hi tarker being an electrician i know a little bit about this the voltage doesnt matter its the current that causes the problems look at the size of the wires connected to the plug on your vacuum cleaner that runs on 230 volts then have a look at the size of the wires going to the battery on your car that is only 12volt a relay uses very little current (amp's) so this allows the manufactures to run skinny little wires to the handle bars and fit very small and lighweight swiches this keeps most of the larger wires on the frame and not running across to the handlebars and restricting their movement if your sure the lights draw the same current as the relay then there shouldn't be a problem removing it but if your not sure are you willing to risk burning out switches, cables or even your bike.

[Tarka]

the voltage doesnt matter its the current that causes the problems

I know that...hence my initial post and also my correcting the post which I had quoted...... read my comments again...slowly....

[teriyakimonkey]

depends on the amperage they draw. a relay has a small coil in it which takes a small voltage and then effectivly can amplify it and just use 1 or 2 pairs of contacts to output the voltage to another aplliance

He he. A relay doesn't amplify a voltage it's used to create a seperate control circuit.

I'm a sparks myself but didn't bother energising my brain relay coil to make the contacts between the common sense input and the "yeah" output.