wiring

[easyrider]

Hi all i want to replace the wiring from my battery ( 120 ah leisure ) to the isolater switch and earth. What size cable would i need please. I had a chat with a young man at halfords and he showed me the battery cables they had but they were about 5 times thicker than the ones currently on my battery. Also what size cable would be needed to run from the isolater switch to the fuse box. As i only have 2 led and one flourescent light and 1bilge pump running of the battery the halfords man told me a 17 amp cable would do. Any help/info would be much appreciated. Thanks

[dnks34]

I would go for slightly bigger than you need, its all about what your appliances can draw if all used together not what the actual battery size is. Id go for the next size up from 17amp if your not planning on adding anything more to the system just to leave a reasonable margin. Halfords is probably not the cheapest place to be buying cable but I suppose it depends how much you need.

[mbird]

Best place for advice like this is Brian Wards in Brundall. If you measure the lengths you need, they will make you up proper battery cables while you wait with heavy duty crimp connectors (and mention the forum to get 10% discount!). Just had all mine done, but with 5 batteries, went for 40mm2 cable.

[Viking23]

When we had one battery, and an electric start outboard engine, we used 16mm2 cable from the Battery to the isolator switch, and to earth bus bar.

We had no problems with three boat safety certificates.

But when I installed a second battery, I used 25mm2 cable, as the Boat safety regs said battery to battery must be a minimum of 25mm2 and battery to isolator a minimum of 25mm2.

It passed last year no problem.

What I don't know is ... would it have passed with 16 mm2 ?

When I placed the question on another forum before fitting the 25mm2 cable it was recommended that the wiring must be 25mm2.

I also have an inverter, but only 800 watts, other than that, just normal lights, pumps etc.

If the electrics are simple, then the outboard engine loom is deemed suitable, but with basic electrics, and a manual start engine, then I'm not sure what could be used and still pass the BSS I guess it depends on the inspector.

[Oddfellow]

http://www.boatsafetyscheme.org/media/164496/bss%20guide%20chap3.pdf

 

 

 

This is the BSS spec covering the areas you are talking about.

[easyrider]

Thanks for the replies. I had a word with a bloke in my local who is an electrician ( industrial ) and he reckons that for what im running of the battery the cable ive got should be ok but if i add any more appliances then go for a bigger cable so i will see how it goes. Thanks again for your replies

[Oddfellow]

Just don't fall foul of the BSS regulations.

[ranworthbreeze]

Hi Andy,

 

I had to edit your link for it to work.

 

Regards

Alan

[kfurbank]

To not fall foul of the BSS I'm fairly sure you will need 25mm cables which in theory are good for about 170amps. It's not about what you think you will need, or draw, but making sure you satisfy the BSS. On my boat I'm belt and braces and have a very short positive to a Mega power fuse holder with a 100A fuse installed. Then the cable runs onto the isolator and from there to the fuse distribution panel where each individual circuit is protected by a separate fuse.

[ranworthbreeze]

Hello Easyrider,

Here is an excerpt from the BSS guide regarding cables. If you have an outboard with the original wiring loom, please checkout the item in the notes.

Regards

Alan

Cable specifications and condition

Exposed wiring could allow short-circuits, sparks and thus

potentially cause fires. Exposed 230/240 V wiring can also give

people on your boat an electric shock.

Are all electrical cables insulated?

Check all electrical cables which can be seen for the presence of

outer insulation.

All electrical cables must be insulated.

Note – this check applies to both a.c. and d.c. cables.

Cables can overheat if they are not adequately sized or rated to

carry the current required by the installation. Battery cables are

subject to high currents, so it is crucial for the prevention of fire

that these are suitable for their purpose.

Are battery cables of a sufficient current-carrying capacity?

Check the size of the following cables.

n battery to master switch;

n battery or master switch to starter solenoid;

n battery to battery;

n engine return to battery or master switch;

n battery to bow-thruster motor;

n battery to anchor winch motor;

n battery to inverter system (over 1000w size).

The battery cables prescribed in the check must be

approximately 25mm2.

Notes – Outboard engines having the engine manufacturer’s original

loom are not required to meet these dimensions.

The actual layout of cable runs may vary depending whether master

switches are installed in the positive or the negative cables.

[Viking23]

Thanks for the replies. I had a word with a bloke in my local who is an electrician ( industrial ) and he reckons that for what im running of the battery the cable ive got should be ok but if i add any more appliances then go for a bigger cable so i will see how it goes. Thanks again for your replies

What is electrically safe in a non marine environment, cable sizes, currents and suitable fuses etc and can even be backed up with calclations, bears no resemblance to what the BSS requirements are, or indeed how they are interpreted.

In my opinion, if you are going to start the job, then do it with the right size cables from the beginning.

I had to redo mine, thinking that 16mm2 cable was suitable, and redo with 25 mm2 cable when I fitted a second battery.

I even bought cable that was marked 25mm2 , as the new modern thin insulation cables are a lot smaller than the older types.

To be safe, and be certain of passing the BSS, I would use Red 25mm2 cable from the battery to the isolator switch. Use Black 25mm2 cable from battery to a 0 volt busbar, (0volt stud). Adding a second battery would be easy, with a second isolator and again 25mm2 cable, using the 0volt bus bar for the second battery 0volt return.

Even adding an inverter would be easy later on too.

The wiring looms can then be connected on the other side of the battery isolator, and to the 0 volt bus bar.

For safety, the wiring after the 0v busbar and isolator, need to be the correct size and be protected by suitable fuses, but after the isolator, any size wire, if suitable, can be used.

The information above is from my own experience, and was checked and approved by a BSS inspector on the Broads in September 2014. Other inspectors may have thought differently, and maybe allowed a lesser system, I wasn't willing to take the chance, and have a fail, a delay in getting the work done, and then possibly paying for a retest.

Do it once... Do it right. in my opinion.

My first career, I was an Electronic Engineer, so I am fully aware of electrical systems, I can see where the BSS are coming from, but small boats with outboards and additional wiring can be a grey area, open to interpretation.

I think the BSS "Outboard wiring loom" statement, probably refers to an outboard connected to a battery with no additional wiring.

Oh... and don't get caught out with a battery that isn't securly fixed, and the terminals aren't sufficiently protected.

Good luck.

[16E]

You should also consider the load going the other way to recharge the battery.  You may only draw a low demand over a long period but the charging circuit will push as much as it is rated at back into the battery.

 

OK you have an outboard and I do not know how many amps they can produce.  Perhaps check the spec for your motor and rating your cable against that would be better.