Fuse sizing

[hiluxdan]

Looking to run power to the rear of my truck and want to know about fuse sizing.
Will probably run 6mm single(am told it can take about 50amps) to the rear and split it in a box up the back with a fuse block like rod put up front.
I know i need a fuse at the battery end and fuses in the rear for each accesory but not sure on sizes.
Power is for light, shower pump and eventually fridge.
Am i protecting the accessory or the cable or both?
Do i get a fuse lower/equal to the accessory amp draw?
Very limited in my auto leccy knowledge so some basic instructions would help.
I went to the solar/fridge? website but didn't really get what i want to know.
Thanks
Dan

[rodw]

dan,

I would run the 6 B&S the first time and you will never need to do it again. The 6mm cable ARB used on my rig too light to use for much other than a fridge. Plugged an extension lead into it to get light into the tent but flouro would not start. I suspect too much voltage loss on a long cable run.

I am going to run some heavy cable (6 or 8 B&S)back to the rear for an inverter and pump. I will add a 50 amp anderson plug in the rear which will power a pump and inverter in my removable storage rack and another down on the towbar for a future trailer.
I think I will use a 60 amp Maxi fuse or a circuit breaker at the battery on the Anderson Plug circuit (as the plugs have a max rating of 50 amp). I will fuse the pump and inverter separately.

While I am at it, I will run an extra cable back to the ARB installed points to eliminate the voltage loss, but leave them on the existing separate circuit.

If I started from scratch. and I had a couple of circuits in the back, I'd wire into this main line and fuse each one, but would only use one fuse for all of the cig lighter and fridge outlets with a 30 amp fuse.

You really need to have a fuse or circuit breaker as close to the battery as you can so you can protect against a dead short in the wiring as well as the accessory.

Hope this helps

Rod

[Dluxv6]

Dan
i have gone the other way with cable size, i ran 10 sqmm twin to rear and 35 sqmm to rear for camper trailer, 10sqmm is fuse protected to 30 amp and 35 sqmm to 40 amp . the bigger the cable the better , the only reason i ran twin as i don't rely on chassis for negative
Give me a call if you need help, marc has my number

Drew

[ROLLUX]

there is a formular to work it out

volts = amps x resistance
amps = volts divide by resistance
resistance = volts divide by amps

[olcoolone]

We usually run 3B&S cable to a fuse box in the rear.

The advantage of 3B&S over smaller sizes is if you decide to add another battery in the rear or get a camper trailer you already have a suitable supply.

It takes no extra time to install and not much more for the cable (Adds about $60.0 to the over all cost.

Use a maxi fuse at the feed point from the battery, I don't like using circuit breakers unless a resetable type because if you have a problem nine times out of ten you will not know and when you do find out it will be to late to get anything done, also they do fail....with a fuse it blows and you can carry replacements.

With the battery cable we always run it in 12mm clear PVC tube for added protection and DO NOT cable tie it to brake or fuel lines under the vehicle.

Are you going to run a second battery?

Do it right the first time.

Regards Richard

[hiluxdan]

Thanks for the replies fellas.
Already got the second battery up front so just need to get the power to where i need it now.

Rollux thanks but like i said i'm very limited - to work out a fuse rating, which formula?
Thanks again
Dan

[Dluxv6]

Dan
Fuse rating is determined by cable size,its there to protect the cable in case of shorts or over current draw from an appliance . to work out current draw (appliance), take power output say 100w(total power output of hand held spotlite) divide this by volts (12) and this will equal amps (8.3) so cable must be able to handle this load , so if you put in 10 amp fuse on say 4mm cable the fuse will blow if short in cable draws more than ten amps or if you put in 200w globe by accident the current drawn then goes to 16.6amps and fuse will blow or worse the cable melts down which oftens happens when incorrectly wired with small gauge wire, as i said before go bigger cable than needed and protect with total draw (fuse size), what do you want to power in rear ,eg fridge, lights etc, led lights are great as they pull next to no current compared to incandescent or fluoro , p.s correct me if i am wrong here guys
i have a fridge and fluoro in rear of mine on 6mm cable protected with 15amp fuse, trailer power on 25sqmm protected by 40 amp fuse
Hope this is clear as mud

Cheers Drew

[hiluxdan]

Definately clears it up, thanks.
Dan