Current Drawn...

[Martay]

Hi there,

doing a little vehicle wiring, and ive managed to confuse myself working out the current drawn in the circuit, so i can work out the size of fuse needed and weather the relay is strong enough.

Basically, im using a relay (switched from the high beam) to turn on a set of OE foglights, and a set of spotlights bumper mounted.

Ive attached a bad paint diagram. Its a 12v circuit. Could someone work out the current drawn by the entire setup please

Massive thanks and for all help.

Many Ta's
____________________
Eat well, poo hard
Drives: Cavalier 2.0 16v
Rides: Slightly ratted Honda City Express

[Hex]

I could be well out but if Amps is Watts/Volts your pulling like 17-18 and a bit Amps.
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[Martay]

Yeah thats the 'formula' that i was thinking, but wasnt sure if it was true because of the parallel-ness! I think im making a simple problem complicated!

Anywho, cheers
____________________
Eat well, poo hard
Drives: Cavalier 2.0 16v
Rides: Slightly ratted Honda City Express

[herulach]

Each of those bulbs will only be seeing 6V in that circuit, so not only will they be a nice shade of yellow, I doubt they'll be 55w at that voltage either.

You need to wire it so they all see 12V (or more like 14). in which case each bulb will draw about 4 amps. Add a bit for wire losses and you're looking at a 20A fuse. Make sure you've got some nice fat wire!
____________________
YBR 125>FZS600

[colin1]

power = voltage x current

so current = power / voltage

ie current = 55 x 4 / 12

= 220 /12

= 18.3 amps

herulach is right though you should wire them all in parallel not in series, as it is, they wont be fully lighting up so it will be using more like 9 amps

wired correctly and they would be drawing 18.3 amps, at the moment probably just 9amps
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colin1 is officially faster than god

[Martay]

Awesome stuff

A tad more wiring than i thought, but it'll give me something to do today!

Cheers for the help, saved me from hours of disappointment!


____________________
Eat well, poo hard
Drives: Cavalier 2.0 16v
Rides: Slightly ratted Honda City Express

[Hex]

[Martay]

DONE!

Spent all morning wiring the lights in, and they all work as they should. Rather than having one 12v feeding 2 lights, ive got 4 seperate 12v feeds, one for each light. Each light then has its own earth.
All work at maximum bright-ness.

Cheers for the help. Im really impressed =)
____________________
Eat well, poo hard
Drives: Cavalier 2.0 16v
Rides: Slightly ratted Honda City Express

[herulach]

Is that on your 125? Hope you've got a trickle charger, I'd put money on the alternator not being able to keep up with that current draw.
____________________
YBR 125>FZS600

[Fortuna]

Hi,
I'm an electronics engineer so can offer some assistance.
As has be pointed out all the bulbs needed to be parallel which you've now done.
Using the basic Ohms law formula of I=P/V (I being current, P power and V voltage) we get 18.333 recurring.
i.e. 220W/12V=18.333A.
Wattage is additive in calculations.
As pointed out you need a 20amp fuse.

Not repeating what is written above, just confirming it

[Martay]

[herulach]