Which power cable?

[xpertski]

Hi all,

I need long power cables (+ & -) to run from battery in bench seat to rear to the rear of the electronics in the front console -

Is the below the sort of thing I need? 250A is also available but thought 170A would be enough?

Thanks!

[GuyC]

Yes it would be fine.

It might be overkill though.

If it is just electronics, they don't draw that much power and you could probably get away with smaller (lighter and cheaper) cable.

If the cable length is 10m, you could use 10mm cable and have enough capacity for nearly 20 Amps of power draw before the voltage drop becomes an issue.

I don't have shares in them but 12V planet has the same cable for $6.23per metre. That is pounds and not dollars - my keyboard isn't recognising the pound sign this morning.

Having said the above - if you have the space, weight and budget - bigger is best.

[xpertski]

Thanks Guy!

Just looked on that website, and given you think 170A might be overkill, would 110A be more appropriate and still leave allot of headroom?

[GuyC]

110A or 16mm2 cable would be fine. I don't know how long the cable is between the battery and the console but assuming 10m you'd be able to draw just shy of 30A before the voltage drop started to exceed the recommended amounts. I'd be very surprised if you've got electronics that exceed this.

A fixed VHF draws around 6A on transmit, a chartplotter around 1A so I don't think you'll have a problem with 16mm2 cable.

[Chanchan168]

I used 50mm from my batteries to the isolator and then 35mm from the isolator to the console fuse box. I think that was slightly overkill, but doable

[xpertski]

I actually have some Ripcaflex 25mm2 cables which are about 10 years old I assume, I can’t find any info online but presume it’s quite a high capacity cable, any issues with just reusing that, is age much of a factor?

[xpertski]

Also, i guess if I put a fuse close to the battery on the positive, the size of the fuse would be a limiting factor to the cable anyway? Ie a 30A fuse would mean even if the power cable has a capacity of over 30A, ie 110 A (16mm cable) or 170A (25mm cable) that the current limit of that cable would be 30A, otherwise the fuse blows?

Also I can’t find in line fuses above the size and capacity of the photo below, it is 16mm and rated up to 100Amp (but fuse would be maybe 30amp; should a larger fuse be used?), if I reuse my 25mm Ripcaflex cable, how to connect in the fuse, could the other photo, connector for up to 25mm cable be used to crimp together 16mm one end from the fuse line and 25mm the other from my existing power cable?

[xpertski]

Sorry folks another question ... if the butt splice connector wasn’t the way to go to connect either side of the fuse, should I instead use something like the below? So cut some 25mm cable, run it from battery to one of these, connect the fuse to it then run the other side of the fuse cable to a second junction, the other side of which the 25mm cable continues to a junction inside the console?

[Last Tango]

What on earth do you have in the console that's going to draw 100A + ?

[xpertski]

Originally Posted by Last Tango

What on earth do you have in the console that's going to draw 100A + ?

Hi - you can probably guess electrics isn’t my strong point but learning ... the engine I bought recently had a 25mm set of power cables (which I’m assuming at about 170 amp capacity), everything came off it - for me it will be the usuals: 12 inch finder/plotter, compass, vhf, stereo, nav lights, bilge pump. Guess none of that adds up to much.

So the cables I have are probably well over and above normal capacity needs so perhaps an opportunity to look at some lower capacity thinner cables. If that would be more appropriate then the 16mm (110 amp - yes I know still probably well above needs) would be more than sufficient and I don’t use the old 25mm cable I have. Thoughts on whether that’s a better way to go?

[Chanchan168]

I used 25mm cable for both of my acr relay to batteries and again for my lead running to the console.

I used bep maxi fuse holders for all and 80amp maxi fuses. Well big enough and perhaps overkill.

[xpertski]

Thanks, that’s interesting, will look at those fuse holders.

This is what I was thinking ...

[Chanchan168]

I don’t really see the point in putting in place two distribution posts. If you have enough 25mm cable left just run it all the way to the console and before it gets into your fuse board, place a maxi fuse holder.

Job done.

[xpertski]

Originally Posted by Chanchan168

I don’t really see the point in putting in place two distribution posts. If you have enough 25mm cable left just run it all the way to the console and before it gets into your fuse board, place a maxi fuse holder.



Job done.

Yes I suppose using the maxi fuse holder you used it does away with the in line fuse and the need to use distribution posts to connect up the different cables ...

[Chanchan168]

Saves you a lot of bother and you can put your fuse at either end. Mine is in console just before fuse box. Nice and simple and easy to maintain.

Best of luck and post pics

[xpertski]

Originally Posted by Chanchan168

Saves you a lot of bother and you can put your fuse at either end. Mine is in console just before fuse box. Nice and simple and easy to maintain.



Best of luck and post pics

Thanks, will do

[Chanchan168]

If you need anymore help or assistance, just ask. Plenty on here with a lot more knowledge than me.

[GuyC]

+1 on what Chanchan is saying with the exception that I'd put the fuse as close to the battery as possible.

It looks like you have drawn a distribution post with one large incoming cable and then several outgoing cables. You could do it this way with a number of inline fuses but it would possibly be neater to terminate it at a fuse box. The link below is to a Blue Sea one but there are various different options.

https://www.bluesea.com/products/503...h_Negative_Bus

The key thing to remember is that the fuse protects the cable rather than the equipment but it is normal to size the fuse based on the maximum current draw of the equipment.

If your total current draw is 16A, for example and your cable is rated at 100A, then the main fuse can be somewhere between 16A and 100A. If you use 1.5mm cable between the fuse box and the consumer e.g. nav lights, then the fuse should be somewhere between the rating of the cable (20A) and the draw of the lights (2A). I'd suggest using 5A fuses for everything apart from your VHF and bilge pump where I'd use 10A.

https://www.12voltplanet.co.uk/maxi-blade-fuses.html
https://www.12voltplanet.co.uk/inlin...se-holder.html

Unfortunately, for you, using 25mm cable would force you to use mega-blade fuse holders or similar as they aren't built to deal with cable over 16mm. There's nothing wrong in that but bigger cable tends to give you fewer termination options.

Apologies for the over long e-mail and if I've confused you even further. I'd also like to add that I'm not an electrician but I've done a couple of 12V projects - motorhome and RIB.

[Chanchan168]

Agreed with Guy. As I ran new cable throughout the refit, I used 25mm all the way from the isolator to my bluesea fuse block (same one as guy suggests)

That has a 6mm lug on it and it’s easy to get a 25mm copper tube terminal with a 6mm hole. I used bep maxi fuse holders. If I remember, these also have a 6mm screw down lug. They only cost £17 each and can take up to a 80amp maxi blade fuse. This was placed close to the fuse block just to aid replacement but as guy says, can also be placed close to battery.

https://boatelectricals.co.uk/bep-ma...older-702-mfh/

[xpertski]

Thanks both, parts ordered, will post photos once all connected up [emoji106]