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Jerry Work
November 22, 2022
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Tools for Cutting and Crimping Ends on Large Electrical Cable

Editor Note: In Jerry’s article, The Best of Both Worlds, Jerry showed us how to make a house battery bank with both lead-acid and lithium batteries.  This month he shows you the proper way to make up battery cables for your bus.

One of the most important things you need to do well when working on your bus electrical systems is to properly cut and crimp ends on large diameter electrical cables.  You will normally be working with cables from 4/0 to #10 with 2/0 a common size for high amp circuits like powering your 120VAC appliances and wall plugs through an inverter. 

Wire with two types of lugs. Solid Copper vs. Tin-plated Copper.

These 2/0 cables are nearly a half inch of fine stranded copper wire covered by a heavy insulation layer.  The crimp ends are commonly formed solid copper or tin-plated copper.  Be sure to buy the correct size to fit the mounting stud where they will be installed. 

The crimp must be “gas tight”, basically mechanically fusing the solid copper crimped lug to these fine strands of copper in the wire.  Anything less than gas tight and over time you will experience corrosion and high resistance at these points.

Resistance is the killer of good house electrical performance. Often you won’t see it, but your batteries just won’t produce all the power they could to do useful work for you running everything from your lights, fans, pumps, motors, kitchen appliances and whatever you plug into the wall outlets.

Large diameter cable cannot be cut squarely or cleanly except with a special cable cutting tool.  Anything else will mash it out of shape and/or leave strands uncut. The hammer-on crimping tools rarely will make a gas tight connection and are more likely to make a mess of your cable and the lug.  You want to use a professional crimping tool for that task.  

There are several crimpers to choose from, some mechanical and some hydraulic. I like the large, USA made mechanical units from Temco Industrial.  The cable cutter is 24” long with properly curved forged cutting jaws while the lever arms on the single thrust ram that forms the actual crimp can be extended up to 29” to provide all the leverage you need for a first rate crimp.

The crimper anvil can be adjusted from 4/0 to #10 in US cable sizes and clear up to 400 MCM in metric size cable just by turning the heavy machine screw that moves the anvil closer to, or away from the ram. 

A good gas tight crimp starts by fully inserting the bare cable into the lug with no strands of copper showing on the outside of the lug.  Hold the lug in the “V” of the anvil and move the thrust ram out to just begin to deform the lug.  The ram should be centered on the flat part of the lug.  Make sure the lug snugs up against the insulation and push down on the lever arms to form a really secure, gas-tight crimp.

Now all that is left is to apply a glue lined shrink wrap tape to keep out moisture and your crimp end on the wire will likely outlast you in your bus!

Do not skimp on the quality or size of the cable and be sure it is solid strands of copper or tinned copper and NOT CCA (Copper Coated Aluminum) which a lot of internet vendors offer inexpensively.   The same goes for the cable ends.  Buy the heaviest solid copper or tinned copper you can find in the cable size and mounting stud size you need.  Never mount a cable end on a smaller stud than the size of the lug.  Doing so will create another point of potential resistance. 

I have tried several insulation stripping tools and have yet to find one that really works day in and day out.  I find a utility knife carefully cutting down to but not into the copper strands works best for me. 

One would seldom think something as simple looking as a cable end on a wire would be this important, but it is!  This critical junction between the wire and the mounting end can make the difference between a system that works properly year after year without you ever having to think about it or it can be the source for poor system performance that is hard to diagnose and can drive you nuts.

Some will suggest you solder those ends in place, and many auto supply places will offer to make soldered end cables for you.  Those will look good, and will perform well in the short term, but in a high vibration application like your bus the copper strands can flex and work harden right where the solder stops eventually leading to high resistance at that point.

So, take your time, properly mechanically crimp and heat shrink all your cable ends so you will enjoy maximum system performance and never have to think about them again.

Article written by Jerry Work

Jerry Work spent his professional career in technology management, first as the founder and CEO of two moderate-sized computer software companies and then as the Associate Laboratory Director for the Pacific Northwest National Laboratory (PNNL), one of the DOE multi-program laboratories. At PNNL, in addition to overall Laboratory management, he oversaw the laboratory’s work in the energy, transportation, medical and information technologies.

After retirement, he and his wife Sharon purchased a Beaver Patriot motorhome and began a cold turkey four years of full-timing which they enjoyed greatly. They then purchased a 1907 former Masonic Temple in rural Southern Oregon, restored the building and remodeled it into his studio and gallery on the first floor and living quarters on the second floor. There he designs and handcrafts fine furniture. He is well known for his many articles and tutorials about how to get the most from Festool and other-high end woodworking products.

They purchased the first of what became two fully restored GMC motorhomes, those iconic and swoopy front-wheel drive units from the 1970’s. They found the second of their two GMC’s in an air-conditioned building in Naples, FL, with just 11,000 miles on the clock following a ground-up restoration in 1984. Both of those motorhomes found their way from Mexico to Alaska and from the West to the East coast. He wrote extensively about his experiences with GMC’s and gave many a presentation at GMC club events over the years.

A few years ago they decided to go back out on the road again for longer periods of time than they could support in the GMC motorhomes so purchased a low mileage 1997 40 foot Country Coach Prevost bus conversion which is now home for more than six months out of the year. Visitors always welcome no matter where in their travels is their motto.

You can reach Jerry Work by email at:
GLwork@mac.com

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