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[aprssig] 12V Wiring and Crimping

Dave dave at g8kbv.demon.co.uk
Sun Oct 30 17:34:16 UTC 2011


From:           	Larry McDavid <lmcdavid at lmceng.com>

> The most reliable terminal connections are made by crimping, not 
> soldering. However, the crimp process requires the correct crimp tool, 
> surely not something from Harbor Freight, and correct sizing of 
> terminal, wire and crimp tool.

So why is the second most common electrical failing on older cars etc, 
more often than not, a bad crimp connection?   Especialy on Battery lead 
connections.

(The most common, loose ground connections!)

> 
> Solder wicks down stranded wire and causes loss of flexibility and 
> potential for vibration fatigue cracks in the wire bundle. 

If not done correctly, yes it does.  Done right, not a problem.  The 
biggest problem from soldering the wires, is melting insulation causes 
corrosive gasses to build up, that rot the wire over an extended time.  
If soldering is done, make sure the insulation does not melt.

> Soldering a crimped terminal is a really bad idea because a correct crimp
> will be "gas tight" and not allow solder to enter the crimp zone; the
> soldering temperature will also relieve the retained stress in the crimped
> terminal material that keeps it gas tight. 

So that's why they go green and fail when used in "moist" areas then?

> 
> There is a great deal of engineering, not guess work, in what 
> constitutes a good crimp. Done correctly, nothing is more reliable than 
> a properly designed crimp connection.

As you say, designing is one thing, doing is another.

> 
> Anderson Power Pole connectors are nearly universal in the ham and 
> emergency communications arena here and are very reliable. The key 
> feature that is not appreciated is the spring-steel leaf spring in every 
> PowerPole connector that maintains the contact force. But, realize there 
> are various *size* PowerPole connector shells and contacts, sized by 
> current-carrying capacity. Anderson sells excellent (but, expensive) 
> four-indent crimp tools. PowerWerx sells acceptable "B-wing" crimp tools 
> for PowerPole connectors. Use of a "F-crimp" tool on a PowerPole 
> terminal will distort the crimp end of the terminal and prevent its 
> insertion into the plastic shell.
> 
> We hams are often casual about making crimps and then complain about 
> their performance. We have only ourselves to blame.
> 
> Bottom line: crimps work very well but you must have the correct tools.
> 
> Larry W6FUB
> Retired Molex engineering manager

Ah, Molex.  Second only to "Lucas, Prince of Darkness" in the 12/24V 
electrical chaos stakes.

Get out there and see your ex companys products failing all over the 
place, after very few years.

Come to that, in many industrial equipment install's, sadly Molex is a no 
no, due to known long term reliability issues.  Long term here, means 
over 3 years, by the way, it's worse when there is vibration.

And I have many instances of Molex connectors burning up, when used at 
near their rated currents (within, but near, both AC and DC) for not very 
long (a few months) in these cases, it's not the crimp that fails, it's 
the pin/socket interface that cooks up.

I'm not talking Ham kit here either by the way.

> 
> 
> On 10/29/2011 10:06 AM, Rudy Benner wrote:
> > I would recommend crimp and solder. Don´t forget the fusing. Do it right.
> ...

Always plan for worst case failures, like the battery ground strap going 
bad, and then someone try's to start the engine.  Figure out where the 
cranking current goes!

> 
> -- 
> Best wishes,
> 
> Larry McDavid W6FUB
> Anaheim, CA  (20 miles southeast of Los Angeles, near Disneyland)
> 
> 
> 

73

Dave G0WBX.

Near Milton Keynes, UK.





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