soldering lugs in static conditions - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: May 16, 2020, 07:41:44 am
content: So, the crimp tool is pretty expensive (I want hexagon or gas tight (oval, star), so no hammer tricks) or point deformation for lugs, I don't like their marketing.. multiple vendor research showed me that the only merits of those methods of connection are cost reduction, so going from 50 to 150 dollars is worth it, butI guess it makes sense to use a crimp as per industry standards, but I am afraid much of the demand for crimps in that application is because of automotive and welding applications, where the cable is handled alot or under heavy vibration.How about in a static application, i.e. on site battery backup system or high current internal wiring, or wiring seldom handled?How does the solder joint of a large lug (say 0-4/0) compare to the best of crimps? I know both age.Also, in this kind of large connection, is there any reason to use a different kind of solder alloy? I assume if you use high flex cable, it would benefit from using copper bearing solder, in order to protect the strands. Are there other reasons based on this large geometry (i.e. contraction rates and finishing points?)Good quality hardware and cables are expensive, so I want to make sure what applications I do need to shell out more on for good reason.

author: 2N3055
author_rank: Super Contributor
timestamp: May 16, 2020, 09:27:39 am
content: Sorry but your post is uncensored, unorganized train of thoughts. I'm having hard time understanding what is (are) the question(s).1. Is it solder VS. crimp question?for that answer is crimp. Crimp because of:- solder wicks up the stranded cable, making cable solid and is problematic for breaking (not a problem in really static situation, where you don't bend short cables during installation)- for thick cable quality soldering gets more complicated (and takes longer) than crimp. No flame heating please...- there are inexpensive hydraulic crimpers that will crimp 32 mm2 like butter. Noname ones will do just fine..- On crimp there is no aging, except what it would normally be on cable itself in same chemical environment. Copper compression makes it harder, heating it up makes it softer.- most long term solder joint problems in static application are chemical. Wrong flux, metal interfaces leading to electrochemical potentials.. Soldering alloy embrittlement, copper leaking into alloy..- because how solder wicks up the cable, even in static application, you can break strands even with single bend, while installing cable (that is more likely with fine strands and thick cable).- flux wicks up the cable too.. Is it no clean? Was it activated? How do you check, how do you clean it?So it is crimping is better long term. Less variables, easier to keep uniform quality.

author: Gregg
author_rank: Super Contributor
timestamp: May 16, 2020, 05:41:35 pm
content: I believe this subject has recently been beaten to death here:https://www.eevblog.com/forum/reviews/lug-crimp-hex-vs-indent/Soldering stranded wire to crimp lugs is not a good idea and should only be used as an emergency last resort when a reasonable crimp tool is unavailable and then it should be considered temporary. A proper crimp compresses the copper strands against each other and against the inner barrel of the lug making a far lower resistance connection than solder could achieve. You might think that adding solder to a crimped connection would seal it from future corrosion, but the heat necessary to make the solder flow will relax the compressive forces to the point where the connection may be worse than without the solder. And how do you know there isn’t flux trapped in between the strands that will degrade the connection? Then there is the wicking of the solder mentioned by 2N3055.If you want to seal the crimp, cover the strands with dielectric grease like NO-OX-ID (available on Amazon as well as most electrical suppliers) and then use the heavy heat shrink with the hot glue inside. Another good product is 3M cold shrink. Shrink tubing can make good strain reliefs as well as seals for cables that may experience vibration and handling.If you are looking for the best crimp connections, as used by the 48V telco industry, use the long barrel two hole lugs from a known manufacturer like Thomas & Betts, Burndy or Panduit and use the approved hex crimp dies. To properly use these lugs, strip the wire about 10% longer than the barrel of the lug, stuff the stripped end into a tub of NO-OX_ID, position the lug on the wire the way around you want it, start the hex crimp at the far end from the wire and make subsequent adjacent crimps along the barrel not overlapping. You’ll see the barrel elongating with each crimp and if you have done it right the end of the barrel will butt against the insulation. Do not crimp all the way to the end of the barrel so that the strands deformed by the crimping process are not at the end where they could break. Do a search for ‘long barrel lugs’ to find lots of examples; they are even available plated with lead for use on batteries. They aren’t cheap.For hobby use, there are lots of inexpensive hydraulic hex crimpers on FleaBay like this:https://www.ebay.com/itm/16-Ton-Hydraulic-Wire-Battery-Cable-Lug-Terminal-Crimper-Crimping-Tool-11-Dies/153870511473The dies are soft enough that they can be modified to suit your needs. If you buy one of these, don’t buy the ones that guide the die with a dowel pin because the individual dies rotate and are a pain to use. The ones that align the dies along the sides are much easier to use.

author: coppercone2
author_rank: Super Contributor
timestamp: May 16, 2020, 05:52:49 pm
content: I read those hex crimps are not gas tight by the way, you need oval or star crimps to get gas tight. You are looking at like 1000$ for the tool there. Small crimps have a good reputation because you can get the gas tight ones fairly cheap on small wires. The awesome reputation of crimps has to do with good crimpers doing gas tight seals I think.I don't think its been beaten to death, if the current is carefully determined, the system fused, and good soldering technique used , I thought it might be possible to make something very stable, without going nuts over initial low resistance.

author: tautech
author_rank: Super Contributor
timestamp: May 21, 2020, 07:12:40 am
content: In the good old days tinned copper solder lugs were used on mains switchboards but if course the cables used were of few strands and reasonably heavy as they weren't designated as flexible cables with high strand counts like what we know today.The lugs used for crimps today are not suitable for soldering as they have a peep hole to ensure the cable strands are pressed fully home so any subsequent crimp meets spec.Normally the electrician of old had a small blow lamp of sorts and heated the crimp and fed rosin core solder into it until full and then waited for it to cool. Today he might do 5 or more crimps in the time it would take to solder just one lug.However, crimped lugs are the norm today and offer the benefit that if the screw or nut fastening them is lose, then there is no solder to flow out when the lug gets hot and then the risk of an electrical fire resulting from an arcing joint.In saying that, for years I've soldered heavy equipment battery lead lugs and the like but their high current duty cycle is quite short so they last perfectly well.Fine stranded heavy flexible cables such as welding lead lugs can be successfully home crimped in a good vise using a bolt head as the anvil for an almost star like crimp however as I have a sparky as a good mate the few seconds he takes to crimp something for me I never now take short cuts.BTW, he recently dumped his star crimper and went to a Hex crimper for the better job they make.

author: Ian.M
author_rank: Super Contributor
timestamp: May 21, 2020, 07:46:22 am
content: You can solder modern lugs in an emergency if you lack a tool with the right size dies, however its a royal PITA, as you need pipeclay to prevent solder running out of the peep-hole Tautech described, and need to clamp the lug vertically in a vice by its flat part, with some card so the vice doesn't heatsink the lug, with the pipeclay blocking the peep-hole, and supported by the vice jaw. Its also awkward setting up to hold the wire vertically so it can't move while the joint cools, and you have to strip back the insulation far enough that it doesn't char during soldering, and also wrap a wet sponge round the end of the insulation to heatsink it and prevent it melting. Then after its done, there's a lot of cleanup to do with IPA and a brass wire brush to get burnt-on flux off the lug,+ you will have to re-insulate the extra bare wire, with self-amalgamating tape to build up to the insulation thickness then heatshrink over all.Is it worth it? No, not unless you are miles from civilisation without the possibility of ordering a suitable tool with reasonably quick delivery, and no local businesses with appropriate tooling.

author: tautech
author_rank: Super Contributor
timestamp: May 21, 2020, 08:00:06 am
content: You can minimise insulation charing by filling the lug near to the top with the cable removed but in the edge of the flame to warm it then plunge the cable into the lug and let any excess solder overflow.If not too hot there should be flux in the lug to wet the copper as it's plunged home. A small dwell time on the lug with a soft heat is a good idea to have the solder fully flow around strands.