You can often ‘save’ money by buying conductor terminals from auto parts stores or online retailers like Amazon rather than a marine chandler. However, there is a reason I have put ‘save’ in inverted commas. It is because these savings may well be illusory, and quite possibly turn out to be expensive, and sometimes very expensive, in the long run.
Hidden features
There are a number of not-so-obvious features which differentiate a quality marine terminal from many cheaper competitors. The marine terminal will be tin-plated copper; the low budget terminal may be plated steel, which can easily corrode in a salt environment, or untinned copper, which will develop surface corrosion, or brass, which has less conductivity than copper.
The marine version is likely to have significantly more metal in it for a heavier construction and a longer crimp barrel. The barrel will have its seam welded shut whereas the cheap terminal may have an open seam that spreads out when the crimp is made. The quality terminal will have a flared entry, funneling stranded conductors into it, whereas the cheap terminal will have no flare, with a risk of conductor strands butting up against the barrel’s perimeter and splaying out instead of entering the terminal.
Wire Sizing Conventions
The sizing system for automotive conductors is different from what's used on boats. In North America an automative conductor may be given the same size (e.g., 16 gauge) as a boat conductor, but the former will be constructed to comply with a standard from the Society of Automotive Engineers (SAE) and the latter the American Wire Gauge (AWG). For a given nominal size, the SAE conductor may have as much as 10% less copper. The SAE conductor will also have fewer strands. You put these two things together – less copper and fewer strands – and you end up with a significantly smaller conductor diameter and cross sectional area than with the AWG conductor. An SAE terminal will be sized for SAE conductors. An AWG conductor may not fit in an SAE terminal, with strands splaying out reducing the quality of the connection and potentially shorting to neighboring terminals.
The Right Tools
In addition to using quality connectors, it's important to have the right tools for the job. You cannot consistently make good crimp connections with cheap, low-quality crimpers and other tools. You need to invest in decent tools or borrow them from a friend. Good tools will ensure that your connections are properly made, reducing the risk of future problems.
From time to time, I teach electrical classes in which we practice making crimp connections. I buy a roll of 16-gauge conductor from the auto parts store (this will be SAE) and cheap butt connectors from Amazon. The connectors have short barrels with opaque nylon insulation, so it is hard to judge how far a conductor has been inserted. I have several low budget crimpers from Amazon. I have everyone add a butt connection to a length of conductor, feeding the conductor into the two ends of the butt connector to make a crimped circle. Except for crimps made by people with significant crimping experience, I can invariably pull the connections apart by hand! A simple upgrade to quality crimpers reduces the failure rate substantially. An upgrade to quality connectors with longer barrels, flared entry, and translucent heat-shrink insulation, combined with quality tools, pretty much eliminates the failures.
Conclusion
The connections and terminals in our electrical systems are the principal weak links. We need to do everything we can to make sure they are reliable and resistance free. Whatever the ‘extra’ cost of quality terminals and tools as compared to budget terminals and tools, this will pale into insignificance the first time you have to hire an electrician to track down an intermittent fault resulting from a poorly made crimp connection!
To learn more about making good connections and properly wiring your boat's electrical system, check out our Marine Electrics 101 course!
