Wiring an auxillary 12 volt battery

[Duf111]

Hi All,
I am wiring up a 12 volt battery to power my yet to be installed depthfinder/fishfinder and probably some led lighting for the interior of the boat at some point. I bought a 12 volt battery and this fuse block. The fuse block did not come with any paperwork. I know it is a 10 gang with a ground bus bar. I know the 10 fused posts are the positive leads. I assume I attach a larger (8 or 10 gauge) positive from the battery positive to the post above the fuses with a ring post.

I am assuming I am doing the same with the negative from the battery to the post that runs along the top (horizontally if you keep the fuses on the bottom when you are holding it). It doesn't indicate it but that has to be the ground/negative correct???


So here is my wiring plan.

BATTERY = 8 or 10 gauge => fuse block (positive & negative) = 12 gauge= on/off switch = device

Does this make sense? I am used to wiring houses but this is my first foray into 12 volt boat wiring.

 

[dvx216]

The gauge of the wire going to a device is determined by the fuse for that device.12 gauge wire is good for 15 amps if you are running a designated circuit to a device 12 gauge wire is over kill and hard to work with. look at the wiring in your boat and you will see the most wiring for electronics are no more then 18 gauge wire.

 

[Duf111]

Makes sense, I did look at the wiring and it is smaller gauge. How about to the fuse block itself? I would imagine a properly sized (based on amperage) heavy gauge wire from the battery to the fuse block would make sense yes? Something like an 8 - 10? Although I am used to wiring houses not boats so

 

[dvx216]

if you use a inline fuse at the battery you can size the wire accordingly to feed your aux .fuse block.

 

[ttmott]

Duff111, you don't mention what battery. However, a Group 27 battery, for example, can put over 500 amps out which will burn down just about any wiring. So you really need a circuit breaker or fuse at the battery. 50 amp would be typical then run 8 gauge wiring from the battery to that fuse block. The 8 gauge would be good for around fifteen or twenty feet at up to 50 amps. With this you would be safe for just about any fuse and load combination at that ten gang fuse block. It is also a very good idea to have a switch at the battery so if you do have a problem or want to isolate the battery you can.

 

[Duf111]

Beauty, going to try this weekend. Thx for the advice all! I will update when done

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