wire and fuses ?

what size wire do i need to wire up the spots on my lightbar (4 x 55watt)? and what size inline fuse ?

did electrics at college but forgot most of it as it was 25 yrs ago and never used the theory after the exams lol

Also will it be ok to wire the a bar lights off the high beam circuit ? will i need a relay ?

A=W/V

theres a clue

The Mad Hat Man said:

A=W/V

theres a clue

Click to expand...

Alcohol=Whisky/Vodka

Power = Amps x Volts,

So 55x4 = 220w, 220w / 12v = 18.33 (20A fuse)

You'll need additional relays to switch your 4 lights, although they can be wired to switch as you turn your lights on so not a problem.

Relay wiring guide

As for the wire thickness, im not sure myself, but if you google around im sure you'll find something, or ask at your motor factors etc..

Ollie

The Mad Hat Man said:

A=W/V

theres a clue

Click to expand...

M H M ever so helpful,as allways.:

Hi, I'd go for a 25a fuse as the lamps if all turned on together will pull a surge, as when bulbs are cold they pull more current.
for 18A I'd use 6mm2 cable, 4mm2 would do but 6mm2 will give you less volts drop.
Does your alty have the capacity?, you'd need an 85 amper to keep up with all that and everything else.

gemsdad said:

M H M ever so helpful,as allways.:

Click to expand...

Come off it Gemsdad- a guy that has "done electrics" and cant even remember 'V=IR' or 'W=VI' - its a ****take! Either that or I wouldnt trust him to wire up a plug, let alone spotlights. The wiring up of spotlights is all covered in numerous posts - as well as a write-up in Qs & As. The guy cant be arsed - and if he cant, why should we? Please note who posted the relay info quoted above. I am all fir helping peeps, but they have to try and help themselves.

dr pepper said:

Hi, I'd go for a 25a fuse as the lamps if all turned on together will pull a surge, as when bulbs are cold they pull more current.
for 18A I'd use 6mm2 cable, 4mm2 would do but 6mm2 will give you less volts drop.
Does your alty have the capacity?, you'd need an 85 amper to keep up with all that and everything else.

Click to expand...

Wire rating needed is a minimum of 20Amp, pref 25Amp - 2mm^2 28/0.30 thinwall rated at 25Amp will do fine. Use a 20Amp fuse and see if it blows - if it does then go to a 25A fuse. You will need a Relay rated at 30Amp. Colour to use is Brown from Battery to Fuse, Brown/Blue from Fuse to Relay, Blue and Red (Main beam to trigger Relay, via on/off/on switch) and Red/Yellow from Relay to lamps. Oh - and Black from lamps to earthing point. I would suggest earthing each light individually.

Dunno where you got 6mm^2 from - thats rated at 50Amps!

I wired my spots off one switch, but fed them in 2 banks seperately. The outer two on one fuse & relay, the inner two on another fuse & relay. That way if a fuse or relay goes than you should still have two working spots.

To work out what size fuses/relays/cable you need remember ohms law.

Watts / Volts = Amps

Therefore at 12volts, 2x 55watt bulbs will take a current of 9.17 Amps. Allow extra capacity for wiring/fuses/relays as if you try running them at almost full rating they will die very quickly (as well as run warm/hot).

Hello Chappers Hows tricks ?