Power to Rear

[Brettm357]

I am planning on running my own power from an Aux battery to the rear and want to run an engel fridge a rear worklight and a Arb Compressor (high volume model). What size cable should i be running to rear eg:25mm2 or less or more. Is it better to run an earth as well instead of attaching earth to rear body. Does the earth have to one size bigger than the power cable. Is it true if you attach earth to body it promotes rust

[Valiant81]

Hi Brettm357;
I to have a engle fridge in the back of my pajero and have run 6mm cable from my aux battery through a 30 amp breaker,as well as the fridge i allso have a hf radio,as well as 2mt /70 cm radio and the usual uhf radio,so farf not a problem.
Also run a negitive wire from your aux battery all the way to engle fridge.
Why i use 6mm cable is 4 mm cable is a bit to light for my tranceivers (hf pulls 20 amps on transmitt. and the engle about 3,4 amps when runing ).hope this helps.

[Brettm357]

Are you talking 6mm2 cable 6mm diameter of cable including insulation or 6mm diameter of conductor only

[Valiant81]

Hi brettm 357;
6mm diameter copper + insulation on top of that ,i had about 60 feet of it laying around the work shop (i did car audio a numper of years ago).I used this type of cable as the voltage drop can be if to high will cause my radio to go into protect mode.
Also you could try and use welding cable as this is also a good cable to use and can work out cheaper than auto motive cable.I hope this helps.

[Brettm357]

6mm diameter so thats 3 awg which is the same as 3 b&s correct ????

[Valiant81]

hi brettm 357.
Sounds about right .I was not realy into the differance wire sizes.

[Brettm357]

3awg or 3b&s or 6mm diameter is rated at 215 Amps isnt that overkill

[Valiant81]

Hi Brettm357;
It's not about the current capacity if the cable.It all to do with the voltage drop over the lenght of the cable,if you use too small dia cable the voltage drop can play cause a couple of volts drop over the total lenght of the cable.
Mable not a problem with just a Engle fridge hanging of the end of your cable.but put a work light and maybe a anderson connector for the van,and the total current drawn starts to add up.
Light cable just does not have the current carrying capacity. Voltage drop can increase and can cause heat,to mutch current = more heat = maybe a fire ,not good.
I've always used the heavyest cable i can lay my hands on.
I once wired a new house boat for sound and all i had was a head end (tuner,cd deck anda usb port)and a 50 watt x 4 power amp.and ended up useing twin 6mm power cable from the battery bank at the back of the boat to the helm voltage drop at no load.and i had 13.1 volts. Turned on radio and amp and increased the volume to cliping and the voltage drop INCREASED to2.1 volt .This is why i use the heavyest cable that i can lay my hands on

[brett]

Spot on there Valiant, run the biggest cables you can afford to buy, you can never have too much copper.