There are all kinds of cables and connectors needed to properly wire a solar array to the controllers, batteries, and inverters.
Wire Gauge
It is CRITICAL to use the proper wire gauge, and when in doubt us the largest wire size that the equipment being connected can handle. The cost of the cables is far less than the cost of rebuilding after a fire. In general we find at least 6 AWG to be preferable for most battery connections and 10 AWG for solar array connections using MC4 connectors; though 10AWG is best if panels are connected in series to boost the voltage to at least 40VDC for most runs.
Here is one of many online Wire Size Calculators we like to use as a reference. We also have a quick reference chart for gauges we have in place on some of our systems listed below. Always double-check the latest references and local electrical codes for proper gauge and types of wiring for your location and system design.
Wire Length
Try to use the shortest viable cable length without compromising a safe layout for the system. Shorter cables introduce less resistance leading to lower losses via heat. They also help present better accuracy from monitors and charge controllers when sensing voltage. This is especially important when wiring DC systems at lower voltages (12 volt especially).
Wire Quality
While the wire thickness is critical, not all wires are created equally. The conductor material is just as important and one should NOT overlook the insulation as well. In our opinion only COPPER or tinned copper should be used, never aluminum or copper clad aluminum. While the later is technically viable there are a lot of details you must fully understand, such as mixed-metals corrosive effects and thermal expansion differentials, to properly employ aluminum without burning everything to the ground.
| Type/Brand | Rally Creek USA Notes | Cost |
|---|---|---|
| Battery Cable 3/8″ Ring to 3/8″ Ring | 3/8″ Bus Bar => 3/8″ Bus Bar 3/8″ Bus Bar => Battery Shunt/Monitor | |
| Milapeak 6AWG Marine Red/Black Pair 1ft / 2ft / 3ft | We are using the 1ft length to connect our battery monitor to the negative distribution bus bar. Decent cable flex with shrink-wrapped tinned copper connectors. Ships in plastic baggy, fully wrapped in film plastic, with plastic zip tie. Includes cute little note in “broken English” from “Kim”. | 1ft $12 Amazon (na) 2ft $20 Amazon (na) 3ft $31 Amazon (na) |
| Battery Cable 3/8″ Ring to Bare Wire | 3/8″ Bus Bar => Charge Controller | |
| Renogy 8AWG Tray Cable 8ft | We are using a 2ft length to connect our charge controller to our distribution bus bars. Solid heavy duty insulation, double-jacketed. High grade cable. | 8ft $17 Amazon (na) |
| Solar Cable MC4 to Bare Wire | ||
| A Abigail Solar Cable Wire 10 AWG 5ft / 6ft / 10ft / 15ft / 20ft / 30ft | Despite the odd made-up name, these cables are one of the better quality cables and connectors in our installation. They are true double-insulated 10AWG cables. Cable Markings: Ningbo Zhiheng Cable Co.,LTD. Halogen 62930 IEC 131 EN50618:2014 H1Z2Z2-K 1×6.0mm2 -40c to +90c DC 1500V | 10ft $19 Amazon (na) |
Wire Gauge Reference
Assuming copper wires with a 3% maximum allowable voltage drop and a insulation temperature of up to 167F.
| Voltage (V) | Max Amperage (A) | Max Distance (ft) | Gauge (AWG) |
|---|---|---|---|
| 12 | 50 | 4 | 8 |
| 12 | 65 | 5 | 6 |
| 12 | 80 | 9 | 3 |