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Many boaters ask for recommendations on the proper wire size (as measured in American Wire Gauge or AWG values) to use for 12-Volt DC electrical power distribution. I have developed a very simple method to find the proper wire size. My method uses a pre-calculated table of the value of Ampere-feet for conductors of AWG-00 to AWG-16.

I explain the method in detail and how to use the table of values in an article at

Ampere-feet
A method of selection of proper wire size
http://continuouswave.com/whaler/refere ... tion1.html

Excellent article.

Q1: Is there any significant difference when using tinned copper stranded wire [perhaps as compared to using solid untinned copper wire]?

Thanks for the kind words on the article on calculating voltage drop with my Ampere-feet method. I hope you find it useful.

Re the resistance of copper wire that has been tinned: I doubt there is any significant difference compared to bare copper wire. The AWG gauge of the wire is a measure of its cross section. I suspect the bare copper wire is first drawn to a particular diameter, and then the tinning is applied. So a tinned copper wire would have the same or possibly less resistance at DC as a bare copper wire due to the same diameter cooper or maybe same diameter copper plus tinned surface layer.

The effect of the surface material of the wire is not a factor in the DC resistance. The “skin effect” only comes into play at radio frequencies.

The tinning is used to prevent oxidation of the copper wire. When exposed to the air with some water added, copper tends to transform chemically into a copper oxide. Copper oxide non-conductive. The presence of copper oxide on wire tends to cause many problems in interconnecting copper wiring, particularly on boats.

ASIDE: the nature of the numbering of AWG wire size is a reference to how many times the material has been drawn through successively smaller dies. That explains why the wire diameter decreases as the AWG number increases.

The article on the Ampere-feet method of calculating wire gauge needed for a combination of circuit length and maximum allowed voltage drop has been updated to include two new tables.

Table 5 provides pre-computed values for Ampere-feet capacity for the standard copper wire size gauges for a nominal “24” volt system, using 26.4-Volts as the actual battery voltage (or twice the nominal 13.2-Volts for a six-cell lead acid battery), for a two-conductor circuit and three-percent voltage drop.

Table 6 provides pre-computed values for Ampere-feet capacity of standard copper wire gauges for a 12.00-Volt system voltage, two-conductor circuit and three-percent voltage drop.

Ampere-feet
A method of selection of proper wire size
http://continuouswave.com/whaler/refere ... tion1.html

ASIDE
The AWG wire gauge number is proportional to the number of times the wire has been drawn through a narrowing mandrel. That is why the higher the gauge wire number the smaller the cross section of the wire (and the more resistance per foot).