4 Gauge 4 AWG 25 Feet Red + 25 Feet Black ( 50 Feet Total ) Welding Battery Pure Copper Flexible Cable Wire -- Car, Inverter, RV, Solar by WindyNation

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This allows for a 3% voltage drop through the cable, which is acceptable for most automotive wiring jobs (3% of 12 volts = 0.36 volts). It’s a good guide. Select the wire conductor material, either copper or aluminum. You can also use Advanced mode to set a custom material resistivity at a fixed temperature.

Ampacity Calculator - Wire Size Calculator Wire Ampacity Calculator - Wire Size Calculator

Then 5% of the power produced by the solar panel is simply generating heat in the cable. You might decide this is acceptable or you might decide to increase the cable size for your fridge supply. Use the calculator below to figure out the cross-sectional area of the cable, then use the Cable Size Chart to match it to the nearest size.

Select which electrical system you will be using. Either DC/AC Single-phase or AC Three-phase. That means the calculator can be a simple DC wire size calculator, all the way up to an AC three-phase tool.

Wire Size Calculator

Auto cable like the SCA example above also uses the 5mm cable terminology. But auto cable is referring to the overall diameter, insulation included , not the cross-sectional area. If nothing else, this value gives you an idea of how much power you’re losing in your cables. Say you’re losing 5 Watts through your fridge cable, and say your solar panel is producing 100 Watts and powering your system. Voltage drop gets converted to heat in the cable. The lower the voltage drop, the less heat generated. Input what percentage voltage drop is allowable. The smaller, the better, but the limit is 5% to keep devices working properly. Say you run a positive cable from the battery to a compressor. Distance is 2 metres. If you run the negative to ground from the compressor at the compressor, then total cable length is 2 metres (plus a bit for the negative cable).The hotter the cable, the more voltage drop through the cable. If you’re running a cable from a battery under the engine bay, it can get pretty hot… like 70 deg C or more. Change the temperature, if necessary. The value should be the maximum operating temperature that is expected for the wire. gives a cable cross-sectional area of 1.53 sq. mm. This corresponds to a 14 AWG cable in the Cable Size Chart above.