12v Wiring Sizing

[smitch6]

sorry i know lots of ppl post about this, but each boat is unique so always worth checking

I will have  2 x 110ah battery 

6' away will be a fuse box (there will be things running directly from fuse box ie water pump 2.4a , fuse box will also be having everything running from it apart from bilge pump which will have it's own in-line fuse direct from battery )

6' away will be the 8way switch panel  ( this has 4 positive inputs 2 for the switches, 1 for the cig lighter, 1 for aux socket, ) ( this will control fridge 3.7a , 6 x 6 led internal lights, 3 x led nav lights 0.8w , horn, led spotlights 24w , stereo ) it also has a cigarette lighter, 2 usb sockets, voltage display, aux socket.

6' away will be a 12v fridge that draw 3.7a

all the other stuff i will be wiring will be low wattage ie led etc so prob only about 10-20w in total at a guess

what size wiring do i need please, between battery & fuse box 

what size wiring between fuse box & 8 switch panel 

what size wiring between control panel & fridge

thanks in advance

[thingamybob]

The exact size of that wire is covered in the BSS regs. I think for the battery to fuse box it might be 5 mm but I could stand corrected, both wires, positive and negative should be that size. The positive cable should go to a main fuse and then, main switch which should be capable of handling the total current expected. Personally I used car starter motor cable which I believe conforms. All circuits, preferably through a distribution box, should be attached to the out side of the main switch with exceptions such as bilge pumps and alarm systems which should be attached to the inward side of the main switch. All such circuits should be protected by their own fuse and they should not be connected direct to the battery by thin wires. Only the thick cable should be connected direct to the battery.

Anyway, download the regs and they will put you right.

[Oddfellow]

All battery to battery connections must be at least 25mm.

I would put a 70amp cable from a battery to a fuse panel or other distribution panel and then use cables of the appropriate size for each of the circuits you are running from there.