Cable selection help

[borzio]

I posted here a couple of years ago for help with wiring my electric outboard engine to the battery, below is some of the post I made

I have an electric outboard engine that I am going to link to a 12v battery via a 50amp circuit breaker as recommended by the Owner's Manual, The engine is 12v 52A input and 624W Input Power. The manual says to use "6 gauge wire AWG" for cable extension.

The guys on here recommended that I either use 16mm meter tails as I was only extending by 1m, or doubled some 10mm cable from some T&E cable I had at home to make 20mm. The cable would be fixed with no movement, so no wear and tear. This has worked fine.

I'm now wanting to move the battery further forward for a better centre of gravity due to it's weight, and want to extend the cable to a maximum of 3.5m. I ended up using meter tails the last time as the length was ok, but may use the T&E solution due to costs, as I have it already, unless advised differently.
Will the recommendations given above still be ok for the increased distance?
Also if the T&E option is ok would it be beneficial to use both the red and blue + the earth as one cable as opposed to doubling a red cable? I would then colour code each length of T&E to red and blue as appropriate.
Thanks again in advance for advice given.

Read more: //www.diynot.com/forums/electrics/cable-wire-equivalent.325731/#2414221#ixzz2VGujOkBv

 

[EFLImpudence]

Will the recommendations given above still be ok for the increased distance?

What will be the total length including the outboard's cable?

Also if the T&E option is ok would it be beneficial to use both the red and blue + the earth as one cable as opposed to doubling a red cable?

Doesn't matter...

I would then colour code each length of T&E to red and blue as appropriate.

...as long as you do that.

Red & Black or Brown & Blue.

 

[Jackrae]

I'd suggest you go for heavier and more flexible cable since you want to minimise voltage loss. The enclosed website offers a good selection of suitable cable. Go for tinned to minimise corrosion problems.

http://www.vehicle-wiring-products.eu/VWP-onlinestore/cable/batterycable.php

 

[borzio]

Thanks Jackrae. I'll look at the link, cheers

EFLImpudence, thanks also for your advice, the total length of the cable including the outboard will be 4m, I am also using Torberry connectors between the battery cable and the outboard cable, and the circuit breaker is beside the battery fixed to the wall.

 

[Jackrae]

Just a point on the use of individual flexible cables to power high current DC motors.

If supply and return cables are placed loosely in parallel and you then pass current through them, they will tend to move apart - due to opposing magnetic field. Simple tie-wraps of placing within trunking will resolve this effect.

I first observed this when I'd wired up a diesel marine engine using welding cable to power the starter motor. When we pressed the start button the cables (visually) dramatically flew in opposite directions.

 

[EFLImpudence]

If you do decide to use T+E then 2 x 10mm² (20mm²) will be fine as far as volt drop is concerned - 0.46V inc. outboard cable.

To overcome Jackrae's magnetic effect you could use the Reds for positive and Blacks for negative

 

[Porque223]

One tradeoff seems to be motor runtime per charge vs. a lump sum cost for cable.
The motor doesn't start under load = minimal start-up surge, so maybe you could aim for a cable plus connector power loss of <1% or <5% of the motor power.
One option would be that the longer cable has the same resistance as the unextended cable.

 

[EFLImpudence]

0.12V - the same per unit length as 2 x 10mm².


Edit - this was in answer to a question which seems to have disappeared.
Namely the voltage drop in the original one metre of AWG6.

 

[borzio]

Thanks again guys,
Jackrae: interesting about the magnetic effect, I've never heard of it before, so trunking will be used,thanks

EFLImpudence: thanks for confirming the 10mm x2 is ok, that's the route I'll go down until I can replace with a single cable as suggested earlier by Jackrae. 2Reds + 2Blacks it is.
Thanks again guys, you've answered everything I need to know, best wishes all

 

[Jackrae]

Borzio

The magnetic effect I mention will only really be apparent if very flexible cables are used, such as welding leads, and the load current is high. If you intend using something like twin-and-earth the opposing cores are held together by the outer sheath and the cores are themselves quite rigid, so no separation effect will be observed.

jack

 

[bernardgreen]

A demonstration of the effect

https://www.youtube.com/watch?v=kapi6ZDvoRs

 

[JohnW2]

If you do decide to use T+E then 2 x 10mm² (20mm²) will be fine as far as volt drop is concerned

Why not also add in the CPC and get 24mm ?

Kind Regards, John

 

[borzio]

Thanks bernardgreen for the link.

and JohnW2: thanks also , I'm very much a layman to electrics so unless someone else objects technically to your suggestion I will indeed include the CPC it's easy enough to do...I had to Wiki CPC to know what you meant, so thanks for increasing my limited/non existant knowledge by +1 !

 

[JohnW2]

and JohnW2: thanks also , I'm very much a layman to electrics so unless someone else objects technically to your suggestion I will indeed include the CPC it's easy enough to do...I had to Wiki CPC to know what you meant, so thanks for increasing my limited/non existant knowledge by +1 !

You're welcome, and apologies for the jargon - even though this is a DIY forum, many of those here like to see 'correct modern terminology' - as you presumably discovered, CPC is just 'code' for what most of the world would call 'earth'!

If you are going to use 'twin+earth' cable, it certainly would make sense to me to use 'all the copper available to you' - i.e. both the insulated conductors (red/black or brown/blue) and the bare 'earth' (the latter adding 20% to your amount of copper) ... unless, as you say, anyone else can think of any reason to object.

Kind Regards, John

 

[EFLImpudence]

... unless, as you say, anyone else can think of any reason to object.

I've been trying.

411.3.1.1 - no, only joking