How many Amps in 8 AWG ??

[Ecosse120]

I have purchased an electric winch for my lifting keel and yep the leads are to short. I am looking for longer cable and am confused by how many amps I can put through a cable I found in a motor accessory shop (cheaper than a swindler) that rates at 8 AWG ?? Looking on the net it seems to vary from 40 amp to 100 amp. As I want to put 70amp through it I am obviously concerned.

Any help much appreciated

 

[Topcat47]

If you're not using marine quality cable, be prepared to replace it......all the auto cable on my boat went black (corrosion) and in the end almost nothing worked.

 

[Ecosse120]

Thank you Topcat 47, that reminded me to go and look in my Merlin catagogue and guess what a nice table saying that 8 AWG = 68amps inside and 80 amps outside.

 

[AdamH]

Can I suggest that you play it safe and go one size thicker with tinned wire? That way it won't go black and heat up after a couple of seasons or get warm between winch and battery, especially as your battery is likely to be under the cockpit, and the winch below the mast - a long wire with a large current.

Or you could use a trailer winch like I do!

Adam

 

[markdj]

The amount of current you can put through a cable depends on the length of the cabel from the power source.

What is the distance of the cable run and is the wicnh 24 or 12 volt?

 

[William_H]

The amp rating of a wire relating to it's size is only concerned with the heating of the wire and subsequent dissipation of the heat. So too much current wire gets hot like a fuse and plastic coating melts and lets the smoke out. (needs smoke inside to work) (joke) So if it is outside then higher current rating. If it is in a bundle lower current rating. (continuous current long term)
Your main concern is the size of cable you need because the smaller cable gives a greater volt drop. The longer the cable the greater the volt drop. In your case for a winch you will need a cable far bigger than that dictated by max current rating.
Guessing at a return run of 20 metres you may loose several volts with 8 gauge cable. olewill

 

[philip_stevens]

Taking the figures from the West Marine catalogue:-

"8AWG -
Nominal OD, 5/16" -
Weight per 1000', 86# -
Cir. Mil. Area, 16,800 -
Square mm, 8.37 -
Ohms per 1000', 0.62 -
Max Amps, 80 -

SAE wire sizes are 6% - 12% smaller.
Maximum current is 15% less in engine spaces.
If 3 wires are bundles, reduce max amp by 30%.

Voltage drop = Current x length x Ohms per foot."

Going by the West Marine guide, if the round circuit is about 30ft, and 80amps is required with a 10% drop in voltage, then the cable is just over the top end of 8AWG and should be 6AWG, which gives a max amp of 120. If you are looking at a 3% drop, then you would require 1AWG / 245amps max.

As a guide price for 2 core, in US$, 6AWG is $7.59 per foot, and 8AWG is $4.24
1AWG is battery cable at $6.99 per foot per single cable!!

All the above extracted from page 552 of the West Marine catalogue. This is "proper" (tinned copper coated) marine cable.

 

[PCUK]

Find your local welding supplies and use welding cable. Top quality and a fraction of the price anywhere else.

 

[markdj]

Don't use solid core in a boat, use flexible 0.2mm strand or smaller.

 

[PuffTheMagicDragon]

Precisely what I used for my anchor windlass. Batteries are near the engine and the cable runs forward and then back, a total return path of around 14 metres.