Cables, Corrosion and Current Ratings

1
 I have some questions about cable, corrosion and current capacity.
 
I have some corroded cables where they join eye terminals.  I want to get rid of the corrosion and treat the cables so that the corrosion does not return.  Does anyone have tried and true methods of achieving this?
 
Another thing that really annoys me is trying to determine the nominal current capacity of any cable.  For example, the cables that I am trying to treat are about 3.5 mm conductor diameter, which is about 9.6 sq. mm.  Are there any charts that give even an approximation of nominal current capacity for a given diameter or area?
 
The labels on spools of wire are a lot less than helpful.  It is common to find three different manufacturers giving three different ratings for the same diameter conductor.  And no label ever seems to state an area.
 
Do we have any electrical gurus on the list?
 
Les
2
> I have some corroded cables where they join eye terminals. I want to
> get rid of the corrosion and treat the cables so that the corrosion does
> not return. Does anyone have tried and true methods of achieving this?

I have really never heard of this.
Has there been heat involved?
Or high resistance joint?
Battery acid?

If it is at the battery end, vaseline.



>
> Another thing that really annoys me is trying to determine the nominal
> current capacity of any cable. For example, the cables that I am trying
> to treat are about 3.5 mm conductor diameter, which is about 9.6 sq. mm.
> Are there any charts that give even an approximation of nominal current
> capacity for a given diameter or area?
>

You will also need to know the length of the cable for the voltage drop equation.

The only way to work out the cable size is to measure the diameter of 1 strand and then use pi to work out the cross sectional area, then multiply by the number of strands.

This is a big problem in Australia because we refuse to standardise and use the proper SI units. Collyn Rivers wrote a good article on this. Aussie auto electricians have a lot to answer for.






> Do we have any electrical gurus on the list?
>
Well I've worked with it for 38 years.

Phill
3
Phill,
 
You must have magic fingers if you have never has corrosion in the terminal end of cables, particularly at the + post of the battery.  The pair of cables in question both feed into one crimp terminal at the + post.  I think that there might have been heat involved at some stage, which is why I want to get back to clean strands before putting good quality solder lugs on them. 
 
I am looking for the nominal current ratings, not the current over 'X' metres of wire.  Go into any auto place and you find racks of wire on spools and the marked amperage looks like "think of a number".  I can measure the cross section of each wire, multiply by the number of strands and get area - but not while standing at the wire rack in Repco!  I will look at what Collyn Rivers has to say.
 
Les
 
 
----- Original Message -----
Sent: Wednesday, March 04, 2009 4:56 PM
Subject: Re: [Syncro_T3_Australia] Cables, Corrosion and Current Ratings


> I have some corroded cables where they join eye terminals. I want to
> get rid of the corrosion and treat the cables so that the corrosion does
> not return. Does anyone have tried and true methods of achieving this?

I have really never heard of this.
Has there been heat involved?
Or high resistance joint?
Battery acid?

If it is at the battery end, vaseline.

>
> Another thing that really annoys me is trying to determine the nominal
> current capacity of any cable. For example, the cables that I am trying
> to treat are about 3.5 mm conductor diameter, which is about 9.6 sq. mm.
> Are there any charts that give even an approximation of nominal current
> capacity for a given diameter or area?
>

You will also need to know the length of the cable for the voltage drop equation.

The only way to work out the cable size is to measure the diameter of 1 strand and then use pi to work out the cross sectional area, then multiply by the number of strands.

This is a big problem in Australia because we refuse to standardise and use the proper SI units. Collyn Rivers wrote a good article on this. Aussie auto electricians have a lot to answer for.

> Do we have any electrical gurus on the list?
>
Well I've worked with it for 38 years.

Phill

4
> You must have magic fingers if you have never has corrosion in the
> terminal end of cables, particularly at the + post of the battery.

I have never seen it. I have had to replace the battery post connector before due to corrosion.




The
> pair of cables in question both feed into one crimp terminal at the +
> post. I think that there might have been heat involved at some stage,
> which is why I want to get back to clean strands before putting good
> quality solder lugs on them.
>

I would shorten the cable and cut away the oxidised bits..




> I am looking for the nominal current ratings, not the current over 'X'
> metres of wire.

You actually wan't the maximum current carrying capacity of the conductor.


Go into any auto place and you find racks of wire on
> spools and the marked amperage looks like "think of a number".

That's about it Les.



I can measure the cross section of each wire, multiply by the number of
> strands and get area - but not while standing at the wire rack in Repco!

They should have something on them like 14/.032 (14 strands/.032mm dia)
This equates to 3mm stupid Aussie size or 1.3sqmm ISO. Which I think is around 10 amp.



> I will look at what Collyn Rivers has to say.
>
He's probably got a chart somewhere.

.......and buy tinned copper wire. Much better.
5
Gday Les,

Given the cables you speak of are attached to a battery pole, I've never
seen cable deterioration there other than the affects of battery acid.
As you probably know, the age old treatment is a combination of
dissassembly wherever possible, dunking in/pouring on boiling hot water
dosed with bicarbonate of soda and meticulous wire brushing/cleaning and
re-dunking/re-pouring. Obviously if the damage is so great it has
affected cable size, then options left are cutting short/adding an
extension or replacement.

Concerning cable sizes & current rating issues, isn't this sort of
detail adequately covered in the publication by Phills best mate, Collyn
Rivers, titled "MotorHome Electrics"? See Chapter 23, Page 80 through
82, starting at sub-heading "Cable Sizing".

The one parameter you left out in your cable capacity question is that
of cable length. In other words, for any given cable size, the current
carrying capacity changes in accordance with known total cable length.
Equally, for any known current requirement, the cable size changes
depending upon cable length. Bare in mind, these parameters are based on
total cable length of positive AND negative cabling for a given circuit.
Using chassis earth return also helps. So you can appreciate why cable
manufacturers can't give the specific details you are seeking, simply by
reading info from the cable spool. Also voltage drop is a complicating
factor.

A few close examples for you, based on known total cable length of (+)
and (-) cabling in metres and allowing max. 3% voltage drop:

9.1 sq. mm cable handles 200 amp for 1 metre cable run, also 100 amp for
2 metres, 50 amp for 4 metres, 40 amp for 5 metres.

9.6 sq.mm cable handles 70 amp for 3 metre cable run.

Cheers.

Ken





--- In Syncro_T3_Australia@yahoogroups.com, "Les Harris"
<leslieharris@...> wrote:
>
> I have some questions about cable, corrosion and current capacity.
>
> I have some corroded cables where they join eye terminals. I want to
get rid of the corrosion and treat the cables so that the corrosion does
not return. Does anyone have tried and true methods of achieving this?
>
> Another thing that really annoys me is trying to determine the nominal
current capacity of any cable. For example, the cables that I am trying
to treat are about 3.5 mm conductor diameter, which is about 9.6 sq. mm.
Are there any charts that give even an approximation of nominal current
capacity for a given diameter or area?
>
> The labels on spools of wire are a lot less than helpful. It is common
to find three different manufacturers giving three different ratings for
the same diameter conductor. And no label ever seems to state an area.
>
> Do we have any electrical gurus on the list?
>
> Les
>
6
Here is some specs for maximum current ratings;

0.75mm sq 24/0.2 or 11/0.32 = 7.5A
1.0mm sq 32/0.2 or 16/0.32 = 10A
1.5mm sq 30/0.25 or 26/0.32 = 15A
2.5mm sq 50/0.25 or 41/0.32 = 20A
4.0mm sq 56/0.30 = 25A
6.0mm sq 88/0.30 or 85/0.32 = 40A


and as Ken mentioned you have to derate for length, but only if it is voltage critical (eg. fridges)














> Ken <unclekenz@yahoo.com> wrote:
>
>
> Gday Les,
>
> Given the cables you speak of are attached to a battery pole, I've never
> seen cable deterioration there other than the affects of battery acid.
> As you probably know, the age old treatment is a combination of
> dissassembly wherever possible, dunking in/pouring on boiling hot water
> dosed with bicarbonate of soda and meticulous wire brushing/cleaning and
> re-dunking/re-pouring. Obviously if the damage is so great it has
> affected cable size, then options left are cutting short/adding an
> extension or replacement.
>
> Concerning cable sizes & current rating issues, isn't this sort of
> detail adequately covered in the publication by Phills best mate, Collyn
> Rivers, titled "MotorHome Electrics"? See Chapter 23, Page 80 through
> 82, starting at sub-heading "Cable Sizing".
>
> The one parameter you left out in your cable capacity question is that
> of cable length. In other words, for any given cable size, the current
> carrying capacity changes in accordance with known total cable length.
> Equally, for any known current requirement, the cable size changes
> depending upon cable length. Bare in mind, these parameters are based on
> total cable length of positive AND negative cabling for a given circuit.
> Using chassis earth return also helps. So you can appreciate why cable
> manufacturers can't give the specific details you are seeking, simply by
> reading info from the cable spool. Also voltage drop is a complicating
> factor.
>
> A few close examples for you, based on known total cable length of (+)
> and (-) cabling in metres and allowing max. 3% voltage drop:
>
> 9.1 sq. mm cable handles 200 amp for 1 metre cable run, also 100 amp for
> 2 metres, 50 amp for 4 metres, 40 amp for 5 metres.
>
> 9.6 sq.mm cable handles 70 amp for 3 metre cable run.
>
> Cheers.
>
> Ken
>
>
>
>
>
> --- In Syncro_T3_Australia@yahoogroups.com, "Les Harris"
> <leslieharris@...> wrote:
> >
> > I have some questions about cable, corrosion and current capacity.
> >
> > I have some corroded cables where they join eye terminals. I want to
> get rid of the corrosion and treat the cables so that the corrosion does
> not return. Does anyone have tried and true methods of achieving this?
> >
> > Another thing that really annoys me is trying to determine the nominal
> current capacity of any cable. For example, the cables that I am trying
> to treat are about 3.5 mm conductor diameter, which is about 9.6 sq. mm.
> Are there any charts that give even an approximation of nominal current
> capacity for a given diameter or area?
> >
> > The labels on spools of wire are a lot less than helpful. It is common
> to find three different manufacturers giving three different ratings for
> the same diameter conductor. And no label ever seems to state an area.
> >
> > Do we have any electrical gurus on the list?
> >
> > Les
> >