Battery Lugs: Solder vs. Mechanical Fastening
Are soldered battery lugs safer than mechanically fastened lug terminals?
Question: Recently I was looking over a friend’s boat that had lost all electrical power. To my amazement I found that the primary positive cable to the battery had melted all of the solder out of the terminal, which was also loose. The cable had fallen out of the lug and was just dangling next to the battery. Does this sort of installation meet industry standards?
Answer: As long as the soldered lug was installed meeting certain criteria established in ABYC Standard E-10, which addresses issues related to marine storage batteries; yes the connection could indeed be compliant. The diagram above, which comes from that Standard, illustrates what the requirements are. The stripped cable must protrude at least 1.5 times the wire diameter into the lug and then be soldered.
This allowance has been in the Standard a long time. During the last review of the standard I actually lobbied to get this removed from the standard, since I’ve seen exactly what you describe and agree that it creates a potentially dangerous situation. The committee out-voted me and decided to leave it as is for now.
To understand what happens here, you must understand that the primary by-product of excessive electrical resistance is heat. In this case, due to the loose battery clamp electrical resistance was created, and in this case enough heat was generated to actually melt the solder inside the terminal lug, allowing the cable to slip out.
Of all the electrical connections on a boat, the main connection to the boat’s battery is the worst place to allow for an exclusively soldered connection. The ABYC standards even mention elsewhere in the standards that “solder shall not be the sole means of connection at a terminal”.
All I can say is that the group will be meeting again this coming January and I will bring this topic up again. With today’s high quality crimp-type connectors, solder at this connection is the old-fashioned and out-dated way to go.
- Ed Sherman is a regular contributor to boats.com, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. He also is the curriculum director for the American Boat and Yacht Council. Previously, Ed was chairman of the Marine Technology Department at the New England Institute of Technology. Ed’s blog posts appear courtesy of his website, EdsBoatTips.
Tags: ABYC standards, battery lugs, Ed Sherman, solder