dreadnought Posted March 25, 2017 Report Share Posted March 25, 2017 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 Link to comment Share on other sites More sharing options...
Paul C Posted March 25, 2017 Report Share Posted March 25, 2017 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. Link to comment Share on other sites More sharing options...
Chewbacka Posted March 25, 2017 Report Share Posted March 25, 2017 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. Link to comment Share on other sites More sharing options...
bargemast Posted March 25, 2017 Report Share Posted March 25, 2017 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. Link to comment Share on other sites More sharing options...
Neil Smith Posted March 26, 2017 Report Share Posted March 26, 2017 I used 70mm on mine, 560ah batt bank 3kw inverter/charger with under 2mts run and all fine. Neil Link to comment Share on other sites More sharing options...
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