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DC Copper Wire and AC Copper Wire Rules and Guide

BD Batteries recognizes that weekend electricians, and others who are not intimately familiar are usually not adept at the difference between copper wire.

DC Copper wire should be stranded to reduce the resistance and allow flexibility at MUCH larger THICKNESSES. This allows these wires to carry high amperages at lower voltages. BD Batteries chooses to supply it's customers with the highest grade welding wire for DC applications as it is tough, shielded for safety, and designed to carry larger loads.

AC Copper or Aluminum Wire is usually thicker, and can be a single strand as the voltages are much higher than in many DC systems and the frequency modulations (HZ) help to "MOVE" the electricity along these thicker wires. BD Batteries supplies it's clients with UL Listed AC Wire that conforms to Colorado Building Codes.

Back To BD Batteries Wire Available for Purchase

Cable Size

Wire Gauge Current Capacity
Amperage (amps)
Max Voltage
1/0 350 350
2 225 225
4 150 150
6 125 125
8 100 100
10 60 60
12 40 40
14 25 25
16 15 15

Cross reference
of AWG (American Wire Gauge)
sizes to metric (mm)

AWG mm2 Ohms per km
R per KM
Ohms per 10 ft
R per 10 ft
16 1.513.00.039624
14 2.58.540.02602992
12 4.05.4 0.0164592
10 6.03.4 0.0103632
8 10 2.2 0.0067056
6 16 1.5 0.004572
4 25 .8 0.0024384
2 35 .5 0.001524
1 50 .4 0.0012192
1/055 .31 0.00094488
2/070 .25 0.000762
3/095 .2 0.0006096
4/0120.16 0.00048768
Ohms at 10 feet calculation .003408 x ohms/km

DC resistance

As long as the current density is totally uniform in the conductor, the DC resistance R of a conductor of regular cross section can be computed as

l is the length of the conductor, measured in meters
A is the cross-sectional area, measured in square meters
p(Greek: rho) is the electrical resitivity (also called specific electrical resistance)
Copper Electrical resistivity (microohm/cm) 1.678

Ohms of resistance in a material can be measured by a multimeter over a wire. Resistance is a measure of the material's ability to oppose the flow of electric current.

For practical reasons, almost any connection to a real conductor will not show perfect current density, or is not totally uniform. However, this formula still provides a good approximation for long thin conductors such as wires.

AC & DC Voltage Drop Over Length of Wire Calculator

The following calculator calculates the voltage drop, and voltage at the end of the wire for American Wire Gauge from 4/0 AWG to 30 AWG, aluminum or copper wire. (Note: System calculates ANY voltage drop, whether safe or not. CONSULT your local, city, state, and national electrical code or your electrician to decide what is legal before building!
Square or Rectangular Solid Metal Resistance Calculator

Select Copper or Aluminum

Select American Wire Gauge (AWG) Size

Select Voltage

Enter 1-way circuit
length in feet

Enter Load
in amps

Voltage drop

Voltage at load end of circuit

Per Cent voltage drop

Wire cross section in circular mils


Calculate Voltage Drop in Wire

To calculate voltage drop, plug in the values: V = DIR/1000
Where I is the amperage,
R is from the ohms/10' X 100 column left,
and D is the total distance the current travels
(don't forget to add the length of the neutral and hot together - ie: usually double cable length). Design rules in the CEC call for a maximum voltage drop of 6% (7V on 120V circuit).

Cool Wire Tricks

The wire gauge is a logarithmic scale base on the cross sectional area of the wire. Each 3-gauge step in size corresponds to a doubling or halving of the cross sectional area. For example, going from 20 gauge to 17 gauge doubles the cross sectional area (which, by the way, halves the DC resistance).
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The information contain on this deep cycle AGM batteries website is deemed reliable, but not guaranteed. Please verify specific information on marine AGM batteries, rv AGM batteries or auto AGM batteries listed here by calling us direct. We are proud to offer the highest quality AGM batteries and hope you will consider using our deep cycle AGM batteries in the near future!