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I need to modify a small battery jump pack cable, adding a Tee / Wye where shown below. I'm free to cut the cable here, too - i just haven't in case the right solution would benefit from it intact. I have more of this cable, so the Tee can be to more pure aluminum (or also copper / CCA if applicable)

Leads are 8 gauge stranded aluminum with very finely stranded wire. The joint will see short duration high current loads (100A+), similar to the initial design of the device (which was jumping ICE cars)

8 gauge finely stranded aluminum wire

The goal is to have a good, durable electrical connection. The device will be kept out of the elements, but exposed to normal humidity and such - hoping to have it last / not destroy itself with galvanic corrosion, etc.

I'm skeptical of soldering this as there doesn't seem to be an accessible, agreed/common flux+solder pair that works; but I have a controlled iron, a hot air reflow gun, and oxy-fuel, if that's how it should be done. The several other questions on soldering aluminum successfully don't seem to offer a concrete recommendation. Note, however:

  • that the OEM has soldered the wire to copper contacts.
  • Johnson implies that their Alumiweld Tin/Zinc solder is appropriate for electrical use; and also sell a eutectic Sn/9Zn that would help me not outright melt these hair-thin wires. I cannot find an online source, though.

I have also looked into crimping, but don't find much for ferrules intended for aluminum wire - which may be as-expected due to the creep Aluminum will exhibit.

How

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The North American experience in AC mains power is that the key to successful aluminum electrical connections is to a) use a lug terminal which itself has an aluminum body, and b) torque the lug terminal to spec.

What was discovered the hard way is that AL wire with a Cu lug wrapping around it, is bad news. The difference in thermal expansion moves the AL wire from its "elastic" zone into its "plastic" zone, causing it to deform (be crushed), which means when it cools down it is now too loose and can arc from the usual "loose connection" scenario. However with an AL lug wrapping around Cu wire, the thermal expansion works favorably, keeping both wires in the elastic zone for appropriate screw torques (clamping force).

So you might develop a split-shell aluminum bodied lug that would clamp the wire appropriately, that has a screw clamp that can be set to a torque, so the screw is controlling the clamping force, not "bottoming out".

What bedeviled aluminum wire in North America was not corrosion - that's what everyone expected - but rather, the thermal expansion differences. Corrosion is dealt with using "no-alox" antioxidant conductive paste. Code does not require this paste unless the approved splice device requires it.

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  • \$\begingroup\$ regarding split-shell - I can cut the wire, I just left it intact in case it was helpful. I would prefer to buy something off the shelf, rather than fabricate \$\endgroup\$ Jun 16, 2022 at 22:34
  • \$\begingroup\$ so it sounds like you favor screw-lug. Any idea where I can find expected torques? And, I find nothing for 8awg wire. Plenty for up to 10-gauge (gounding bars and similar), and plenty for much larger (service feed wire) ... but nothing in between. Any source or product name you could recommend? at 8.3mm^2, I suppose I could twist several and make it work in a larger lug? \$\endgroup\$ Jun 16, 2022 at 22:36

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