neg/pos cable

[dreadnought]

hi,i`m looking to connect negative cable to my busbar could  the forum help with the sizing please,also the positive power to my fuse board,

the nb is 57ft with all the usual electrical gear on board nothing out the ordinary , many thanks 

[Paul C]

Simple answer: 70mm2

Complex answer: cables are sized taking into account 4 requirements based on mechanical strength, current carrying capacity, voltage drop, availability blah blah blah so we'd need further details on the maximum loads that cable would carry. I imagine the highest load is an inverter (and these vary greatly in power) but you'd need to consider all loads. Most big inverters have their own connection to the batteries, some little ones don't though and go through the "fuse board" (many boats use circuit breakers nowadays, not fuses) so the positive power to the fuse board is going to differ from boat to boat depending on what you call "normal" electrical gear (and distance from batteries, too, of course).

Its like asking how long a piece of string needs to be, except its a wire. And its the width, not the length.

[Chewbacka]

To get you started, the BSS requires a min size of 25mm2.

I have a 2.5kW inverter and a couple of big alternators on the engine, so went for 95mm2 cable which is a bit overkill, but as I did it myself, and the difference in cost for a couple of meters of cable between 50mm2 and 95mm2 was something like £15 I went for the bigger cable.

[bargemast]

29 minutes ago, Chewbacka said:

To get you started, the BSS requires a min size of 25mm2.

I have a 2.5kW inverter and a couple of big alternators on the engine, so went for 95mm2 cable which is a bit overkill, but as I did it myself, and the difference in cost for a couple of meters of cable between 50mm2 and 95mm2 was something like £15 I went for the bigger cable.

It's much better to use cables that are heavier than needed than not heavy enough, I normally do just like you do, just to play safe.

 

Peter.

[Neil Smith]

I used 70mm on mine, 560ah batt bank 3kw inverter/charger with under 2mts run and all fine.

Neil