In article ,
Bruce L. Bergman wrote:

On Tue, 27 Oct 2009 16:55:17 -0700, "T.Alan Kraus"
wrote:

Scenario facts: a piece of stranded copper battery cable about 3.5"
long with two soldered connectors at each end, used for ground
connection on a motorcycle battery. The cable broke in the middle with
what looks like a stress fracture. Cable was flexed many times, every
time battery had to be taken out or when battery had to be disconnected
for electrical tests or electrical modifications to motorcycle wiring.

Son contends it is the fault of soldering connectors onto cable, which
heat stressed the cable. I think it is copper work hardening when
flexing cable, thinking that heat if anything (maybe to low) would help
anneal copper.

Son's right on this one - the solder will wick an inch or two up the
wire when it's heated. If the whole cable is only 3-1/2" long there's
only about an inch in the middle that can do any flexing. And when you
concentrate all the bending flex like that...

And I'll bet the battery was moving relative to the chassis while
riding, so it wasn't just from removing and replacing the battery. You
can't make it too rigid or things will break over time.

Saw your post already about making a longer cable and leaving a slack
loop, that should be a permanent repair. Don't solder the new lugs,
but seal battery acid out of the crimp connections. Heat-shrink
tubing with hot-melt glue sealant inside might be the ticket.

What I used to do with battery connections was to splay the copper
strands slightly, force some silicon grease between the strands, twist
the strands back together, and crimp or bolt the terminal onto the wire.
The clamping pressure forces the grease out of the actual contact areas,
allowing metallic contact, while the grease fills the space between the
strands, excluding the acid.

It also helped a lot to smear the battery post and the inside of the
battery clamp with this same grease, keeping the acid from wicking up
into the space between post and terminal.

The silicon grease I used was made in the 1970s by GE as a dielectric
grease, to exclude water and dirt on the insulators of high-tension
transmission lines, and is now available as for instance Permatex
Dielectric Grease
http://www.permatex.com/products/Aut...intenance_repa
ir/electrical_system_maintenance/auto_Permatex_Dielectric_Tune-Up_Grease.
htm.

Joe Gwinn