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Discussion Starter · #1 ·
With the exception of bus bar connections, connecting batteries seems to always use compression lugs.
Is there any reason why mechanical lugs (a screw providing compression type) aren’t used?
What are the advantages or disadvantages?
Thank you for your answers.
 

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Lots of big LI batteries provide a threaded hole for a terminal rather than a lug.

Some a threaded stud, so the pressure on the cable's ring termination comes from a nut rather than a bolt. In either case a torque spec is usually given, since the disadvantage in either case is, over-tightening can damage the terminal

which is harder to do with a compression lug.

Is that what you mean?
 

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Discussion Starter · #3 ·
I was thinking more about the cable side of the terminal, how the cable is attached to the terminal. If you attach the terminal with a crimper, is that a better or worse connection than using a mechanical terminal where the wire is compressed by a screw.
My understanding is that the goal of a good terminal connection is to squeeze the wire so hard all the air and gaps inside are eliminated. I used a small hydraulic crimper on 2/0 welding wire and then cut it open. It looked like a piece of solid copper wire, no gaps.
I can’t imagine a screw providing that kind of compression, but I see mechanical lugs up to 4/0 wire and 600V and I’m guessing that level of power is unforgiving of weak connections.
If it’s good enough for those levels is it good for our car builds?
 

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Hammer-style crimpers are not consistent.

Best is crimping with prooer tools and supplies, no solder needed, in fact can be counterproductive.

Check out marinehowto.com crimping posts.

If you don't want to invest in good crimpers I reco genuinedealz.com, great value in custom cables
 

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Crimping a lug actually cold-welds the metal together like it's silly putty; it becomes a single piece of copper. If you cut open a lug you'll see this; a properly done crimp will be impossible to disassemble without a grinder.
 

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Screw crimp / lugs aren't very good for a consistently good connection.
You may want to consider using copper tubing with an ID about the same size as the cable conductor you're using.
One of my battery cable connector self destructed (ICE van). I bought a marine battery terminal and had a copper tube scrap. I hammered one end of the tube flat, and drilled a hole in it. I was going to solder the cable in it, but woulda had to take the cable out - so just did the best I could at crimping it. It's long enough so everything works ok - and it's been like this for 4 or 5 years. It's best to crimp it as tightly as you can - when done right (nicely?) the copper will actually 'flow', fill voids and become as one piece. I've done before where I've hammered it around a 1/8"(?) steel rod and it looks almost like it was done with a crimping tool.

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Screw crimp / lugs aren't very good for a consistently good connection.
You may want to consider using copper tubing with an ID about the same size as the cable conductor you're using. One of my battery cable connectors (ICE van) self destructed, so I bought a marine connector and used a length of copper tubing. I hammered one end flat, and drilled a hole in it. I was going to solder the cable in it, but woulda had to take the cable out - so I just did the best I could at crimping it. It's long enough everything works ok - and it's been like this for 4 or 5 years. With a good tight crimp the copper flows and fills voids to become like one piece. I've done others where I hammered it around a 1/8"(?) steel rod and it looks almost like it was done with a crimping tool.

 
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