T&T: Battery cables- welding leads, and where goeth the wily electron.

[Ken Bloomfield]

Hi Ron,

Like you, I too started college in the "dark ages" (in my case about 46 
years ago).  Those were the days that we couldn't even trust an electron's 
direction on a one-way street.  They also used to say that current flowed on 
the surface of wire, but that is only progressively true in higher frequency 
circuits.  The ultimate case is our radar waveguides where it is all on the 
surface (albeit the inside one).  In the case of DC circuits, the current is 
homogenously conducted all through the wire.

Not sure that matters a damn, as corrosion still does its dirty tricks 
anyway.  It doesn't much matter if the current is all through the wire when 
it has to make the leap from wire to connector by the surface contact.  I 
would say, however, that in all likelyhood it is seldom that current is 
diminished by the loss of copper due to corrosion (since volumetrically it 
is very small %), and conversely it is very common that this last "hurdle" 
is the show stopper as the electrons endeavor to get from the wire into the 
connector via surface contact.  For long life, I like a crimped connector 
that has also been soldered.  The solder to wire and solder to connector 
fusion is so intimate that corrosion cannot "sneak in" there.  It is also 
true as you point out that if the solder "wicks" into the stranded wire 
outside the connector, it can create a hard spot subject to the same kind of 
vibration cracking that a solid strand wire would see.  However, this is 
usually pretty easy to remediate, especially if the wire breaks out of a 
harness.  Judicial whipping with either whipping cord (old school) or wire 
ties will usually provide a secure anti-flexing solution.

I guess next, I will discuss how many angels can dance on the head of a pin, 
or some other equally scintillating topic.
{;-)

Cheers,
Ken.

Ken Bloomfield
Cell# 865-293-2174
MTOA# 2062
AGLCA# 3529
M/V Tellico Lady, 50' Marine Trader-Walkaround
Maryville, TN


----- Original Message ----- 
From: "Ron Rogers" <rcrogers6 at kennett.net>
To: "Al Thomason" <thomason.al at gmail.com>; 
<trawlers-and-trawlering at lists.samurai.com>
Sent: Saturday, April 12, 2008 8:14 AM
Subject: Re: T&T: Battery cables- welding lead


> As I understand it, current flows along the outside of a wire. Therefore,
> corrosion would diminish the wire's ability to carry current. In the old
> days (40 years ago) we used to employ uninsulated, zinc-plated connectors
> and it was SOP to solder the connectors on the plain copper wire with no
> mechanical crimp on the connector barrels. Then we would tape the joint. 
> Of
> course, since you first tinned the wire, you ended up with too rigid a 
> joint
> by today's standards so you used many wire ties to limit the strain on the
> joint.
>
> Ron
>
> ----- Original Message ----- 
> From: "Al Thomason" <thomason.al at gmail.com>
>
> | FWIW,  My boat had welding cable with crimped ends for the starter. 
> Long
> | story short:  I was dropping about 2v over a 6' long cable.  This was
> | dropped over the length of the cable, not just at the end.  I replaced 
> it,
> | and opened the cable up.  The small wires were all green throughout.  My
> | suspicion:  Corrosion had gradually made the small wires smaller.