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Basic Tutorials: Wire & Cables
Correct wire sizes are essential
To connect the components of a Solar Energy System, you will need to use correct wire sizes to ensure low loss of energy and to prevent overheating and possible damage or even fire. Below is a chart showing the required wire size for wire lengths to connect the solar panels to the Charge Controller. Use these numbers for a 12 volt system to achieve a 3% or less voltage drop.
Always use larger cables than you think you will need The top row represents the Wire gauge size, the left column the number of amps the solar panels are rated at, and the grid cells show the distances in feet between the Solar Panels and the Charge Controller.
For example: If you have 3 solar panels rated at 6 amps each, mounted 30 feet from the Charge Controller, then you would move down the chart to 18 amps (3 panels * 6 amps), and across to 32.5 (closest to 30), and then up the chart to #4. You would need at least #4 gauge wire (awg) to move 18 amps 30 feet with a minimum voltage drop of 3% or less, an acceptable loss.

If you can't find the exact numbers, choose either a larger gauge wire (smaller number) or select a distance longer than your actual distance.

Wire chart for connecting 12 Volt solar panels to the Charge Controller
This chart shows wire distances for a 3% voltage drop or less. These distances are calculated for a 12 volt system. Multiply distances by 2 for a 24 volt system. Multiply distances by 4 for a 48 volt system.
NOTE : This chart is an approximate distance reference and is a little conservative. For a much more accurate wire sizing, use our new Wire Size Calculator tool. It can calculate wire size using 3%, 4%, or 5% losses plus you can select 12, 24, or 48 volt systems.
#12#10#8#6#4 #3#2#1#1/0#2/0
422.736.357.891.6146 184232292369465
615.224.238.661.197.4 122155195246310
811.418.228.945.873.1 91.8116146184233
109.114.523.136.758.4 73.592.8117148186
127.612.119.330.648.7 61.277.397.4123155
146.510.416.526.241.7 52.566.383.5105133 45.958.073.092.0116 40.851.664.981.9103
204.67.311.618.329.2 36.746.458.473.893.1 29.437.146.859.174.5
303.14.87.712.219.5 24.530.938.949.262.1
352.64.26.610.516.7 20.926.533.442.253.2
402. 18.423.229.236.946.5
Connecting the Charge Controller
After you connect the Solar Panels to the input terminals of the Charge Controller using the above chart, you can use the same size wire to connect the Charge Controller output to the batteries since these wires will carry no more current than the solar panel wires and will probably be located pretty close to the batteries anyway.
Connecting the Power Inverter
The Power Inverter is next. Both the Power Inverter and the Batteries require the largest wires in the system. During operation, the AC produced by the Power Inverter draws considerable amps from the batteries. Not only are very large wires required, but they should not exceed 6 feet in length to reach the batteries. These wires are like the large battery cables in cars. Use the largest size possible. An AC appliance drawing 10 amps (like a microwave or vacuum cleaner) will require 100 amps at 12 volts DC. Even large cables will get warm. Don't skimp here.
Connecting the Batteries
The batteries are last. They will also require very large cables like the large battery cables in cars. The full current to the loads and also the full charging current flow thru the entire battery bank. Connect all the batteries with large high quality cables. Check out the Battery Wiring Diagrams tutorial for examples of Series and Parallel wiring techniques that allow the use of battery voltages of 2, 4, 6, or 12 volts. Our new Battery Bank Designer tool will show you how to connect the batteries for these various voltage systems. Series and Parallel wiring examples
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