12v amperage/power load for off-road lights.

[Pskhaat]

I'm looking at putting some more/different off-road lights in. Starting on the wiring.

Looks like some of the highest-wattage off-hwy lights are ~100 watts. Is that about standard? Hopefully I can afford some HID-style and reduce the amperage.

If @~100VA that means each of them draw nominally a little more than 8 amps @12VDC, right? I am investigating a relay bank so want to make sure I can handle the proper load.

 

[Mike S]

You should calculate the wire run for the total rated amperage X 1.5, and go one size larger. relays are available to handle up to about 30 amps. Fuse the wire at 1.5X the actual max amperage load.

 

[BiG BoB]

It's not the "correct" method, but here's what I do...

Pretend that the vehicle runs on 10v

10 is an easier number to divide by, and in this case 100W is 10A

It also gives you a nice safety margin

Sean

 

[Pskhaat]

relays are available to handle up to about 30 amps

My current concern is that the relay rack I'm looking at only has 20A@24VDC relays. I would assume that these relays are VA (watt) rated? Thus, 480VA right; at 12v that is 40A rated?

Stepping up to the 30A@24VDC rack gets quite spendy for some reason...

 

[crawler#976]

Scott,

The 35W HID's from Checker Auto are about $250.00 for a pair including tax, and worth every dime. They draw less amperage than one 100W KC Daylighter or similar light, and are a lot brighter.

Mark

 

[Mike S]

My current concern is that the relay rack I'm looking at only has 20A@24VDC relays. I would assume that these relays are VA (watt) rated? Thus, 480VA right; at 12v that is 40A rated?

Stepping up to the 30A@24VDC rack gets quite spendy for some reason...

You need only concern yourself about the load on each switched circuit. If you design the circuits so that only one pair of 100W lights is on each one, then you will have a load of 2 X 8.333 Amps (or 16.666 Amps total) on that circuit.

Amps X Volts = Watts. 20A x 24V = 480W, 480/12 = 40 Amps. Make sure that they switch at 12V.

M

 

[ntsqd]

I don't know what relays you're looking at, but 30-50 amps in a Bosch pattern (typical automotive) relay is fairly inexpensive. I just ordered 10 of them at about $8 each.

 

[Pskhaat]

I don't know what relays you're looking at, but 30-50 amps in a Bosch pattern (typical automotive) relay is fairly inexpensive. I just ordered 10 of them at about $8 each.

It's a switched remote-control relay bank with relays on the PCB (non-pluggable ); not specifically the relays themselves that are of price.

 

[PhulesAU]

I went for the cheap route. Except for the SIZE...... do the math you get a few more lumins out of them. I've had them for about 6 months and No problems, even after a gravel bath.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=95059