Better than butt splices - check out 'Solder Seal' splice from Haisstronica

For marine connections or anywhere you need a guaranteed electrical connection that will be immune to oxidation and corrosion, my new favorite go-to is solder seal connectors. Haisstronica makes the best ones I've found - the solder doesn't melt under normal current and the joins are incredibly strong and waterproof. Great for boat, RV, automotive, and more. Use anywhere you'd use a mechanical butt splice connection.

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Editing: Vengeance Edits

[TheNetGuy]

Considering one? Using the affiliate link above helps me find new products for my wife to complain about in our entry way :)

[perryallan]

I question their effectiveness if the wires are a little bit contaminated with something. I recently did a project where I soldered 8 sets of 20 gauge stranded wires from a battery holder to a 20 gauge flexible cable with the right connector end and it took a lot of flux (and a lot of wasted solder dropping off given it was rosin core solder) to get the solder to bond to the wire from cable side of the assembles .

These were freshly stripped wires as I was building a set of 8 Li-Ion battery sets using replaceable battery holders so you can replace the individual battery cells every few years instead of buying a certain manufactures > $300 each batteries (Battery holder with protection circuit board, extension cable with desired connection, Li-Ion flat top batteries, shrink tubing, solder, 33+ electric tape - about $55 Ea).

That is not the 1st time that I have run into wires that did not solder easy and needed a fair amount of flux.

[mrcryptozoic]

Never butt join anything (except maybe if you're a GOOD welder).