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Open Roads Forum  >  Tech Issues

 > Jumper Cables A Jumble Of Compromises

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MEXICOWANDERER

las peñas, michoacan, mexico

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Joined: 06/01/2007

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Posted: 09/14/20 04:07pm Link  |  Quote  |  Print  |  Notify Moderator

DON'T ALLOW THE 2ND VEHICLE TO CRANK WHEN YOUR ENGINE IS RUNNING

RUSSIAN ROULETTE FOR ELECTRONICS

Gdetrailer

PA

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Joined: 01/05/2007

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Posted: 09/15/20 04:44pm Link  |  Quote  |  Print  |  Notify Moderator

K Charles wrote:

ADT7976 is 4 gauge 500 amp


Most "jumper cables" you find at Walmart and most other retailers are 6 ga or even 8 ga.

I HAVE burned up 6 ga jumpers on a cold winters day.

Even worse yet, most premade jumper cables now days are cheating, using Copper COATED ALUMINUM (CCA)wire, manufacturers SHOULD label it as CCA but often they do not mention that it is CCA. Manufacturers electrically (electroplate) a very thin layer of copper over top of the aluminum wire and you simply left with a much lower capacity Aluminum wire with a fancy copper coat. The copper coating is to little to make any resistance or capacity difference over plain aluminum, it is solely there to stop the aluminum from corroding into a worthless high resistance white powder.

That makes that 4 ga copper coated ALUMINUM wire more equivalent to 6 ga all copper wire as far as Ampacity goes.

Good example is this one..

HERE

The price for the above is $20 for 20 ft ga jumper cables (40 ft of wire when adding pos and negative).. Box and description does not mention CCA but it is in expensive compared to all Copper wire for 4ft in that ga.

One reviewer in the link above measured the resistance of the jumper in the above link..

This is what they found..

"I am pleased with the 20-foot 4 Gauge jumper cable set made in China by EPAUTO. The cable is copper coated aluminum, known as “CCA.” It took microscopic examination to see the aluminum core in the fine wires forming the cable. I measured the resistance using an Agilent 34401A 6.5 digit bench multimeter in 4-wire resistance mode to be about 0.4 ohm per 1000 feet which is appropriate for #4 copper coated aluminum. This is equivalent to #6 copper. I was hoping this cable was 100% copper, but it was not advertised as such. "

4 ga copper wire can run $2 per ft easily, 40ft would be $80 not including the 4 clamps..

Yeah, I am aware of the "skin effect", please do not go there for DC. Skin effect only comes into play with AC (Alternating Current) and at HIGH FREQUENCIES (think RADIO TRANSMITTER FREQUENCIES).

OP is simply USING something (the wire) he already has laying around instead of buying a new cheaply made and less superior jumper cable.

MEXICOWANDERER

las peñas, michoacan, mexico

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Joined: 06/01/2007

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Posted: 09/16/20 11:12am Link  |  Quote  |  Print  |  Notify Moderator

I gave 1/2 of a set of jumpers to Celsi. From a jumper connected to a group 4 3-cell truck battery to a six inch wilton vise. It's for soldering starter motor leads with 100% lead which must be used in starters. I have the other ten feet which also have cheap copper coated steel parrot jaw clips. He has a pair of carbon 1/4" rods. The soldering is direct to the huge field coil steel starter case.

This is how I soldered the 350MCM lugs so many years ago in the gen shed. 350 MCM is a bit less than twice the size of 4/0 cable.

The wire in the small cable is authentic pure copper high strand count 8AWG. It was not easy nor cheap to find on eBay.

After modifications it will be connected to the Gigawatt 55 amp charger.

The steel parrot jaw clamp teeth will be lead coated just like the DLO 4AWG cables. And 12 AWG shunt wires within the jaws. Also to be multi coated with Bed Liner inside and out.

Aluminum conductor cannot be heat treated to eliminate brittleness. Aluminum's fatal flaw. Bend fine strand copper bundle back and forth until your finger's ache. Bend aluminum back and forth a few dozen times unil it fatigues and breaks. Vibration will also embrittle aluminum.


lightly used wire need not be concerned. Wire used for commercial jumping needs to be concerned, especially if coiled.

High voltage power transmission cable is aluminum. BUT It has rope stranded STEEL CABLE as a core.

Building any electrical assembly to tough grade specs is time consuming and a labor of love. Building to endure decades is an art form. This is Mexico. A place where garbage aluminum cables cost fifty dollars not $25 like in the states. I would be pleased if my cables last until the turn of 2100. My COVID delayed super charger for use in Alaska, has 2 chargers inside. The main charger is a 170 amp unit, the secondary is a 36 amp Megawatt for use with a tiny generator. It uses, owner supplied 2 AWG arctic grade charge lead cables. High speed blowers (brushless, German double ball bearing) can carry away an enormous amount of heat. This multi-charger project is missing mil-spec switches. Except for the 12 AWG SOOW power cable and battery leads color-coded 100% silicone wire is used throughout.

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