One of the best lessons I learnt well over a decade ago while building my first dedicated Hi-Fi system was no matter which brand of speakers, preamps and power amps, phono stages and CD transports you go for, you’ll need the best cables you can afford to get all the parts wired up.
First, I was hesitant about spending so much per metre of thick cable, but eventually came round in avoiding the poor man pays twice logic. The same applies when you’re building your solar system from the ground up. You’ve invested so much in panels, chargers, charge controllers, batteries, inverters, voltage monitors and all other goodies (not to mention the splurge on a campervan or RV for portable solar), that cheaping out on cables, wires and connectors just doesn’t make sense. Sure, you could save a few cents now, but in the long run, any damage might run in the thousands.
Wires vs Cables
Though these two terms are used interchangeably in general conversation, there is a difference. A solar wire is a single conductor, while a solar cable usually consists of two or more conductors bound together.
Solar wires are used to connect the individual parts of a solar system. This includes the solar panels and the batteries and everything in between like inverters, chargers, charge controllers and voltage monitors. Efficiency and safety depend on the right wires for the right parts.
Build and Materials
Wires in photovoltaic (PV) solar systems can come in single-piece or solid metal cores, or in multiple strands, effectively meaning multiple conductors. Stranded wires are used where better conductivity is needed, like between batteries and inverters. Single or double core solid wires are generally used in connecting solar panels in series or parallel.
In terms of materials, metals with high conductivity are chosen. Though silver is the best conductor, it is rarely used because of the high cost. The best alternative is copper, which has decent conductivity, meaning it can carry the required current and also withstands changes in temperatures from cold to hot without any wear. The best affordable wires are tinned copper with an outer tin layer. A cheaper alternative to copper is aluminium, though these wires are not recommended in solar setups due to their inferior qualities when compared to full copper wires. They conduct less current, are prone to damage in temperature changes and are less flexible than copper. To avoid any unwanted repairs always go for copper wires.
Wire cores or bound strands are protected with an outer layer of insulation. For solar uses, wires and cables have insulation and sheathing that resists UV rays, moisture, heat(fire) and chemicals. Insulation layers are mainly reinforced polymers. More expensive variants have thicker insulation layers of high-quality materials. Wires also come in various thicknesses depending on the amount of current they can transfer. This correlates with the amperage rating, with the higher number meaning more current. Consider what you are connecting, and at what distance, as amps are lost in longer cables. A cable of the appropriate thickness and length will not strain or overheat or significantly lose output.
For ease of installation, wires are colour-coded. Red wires connect directly to the positive pole, while white or blue is used as a ground on the negative pole.
Types of Solar Cables
There are two major types of solar cables – DC solar cables and AC solar cables. DC cables usually come in a solid single-core configuration, varying in thickness or gauge. There are three main sizes of DC cable – 2mm, 4mm, and 6mm solar cable, with the thicker the cable the higher the current rating in amps. DC cables are of solid cores, since strands make no difference in conductivity as compared to AC cables. DC cables are found in interconnections in solar panels and a ‘string’ DC 6mm solar cable connects panels to one another. Main DC cables, often consisting of a twin-core setup, are used to connect the panels to the battery. Connectors and adapters, such as MC4 or Anderson plugs are also used here.
AC cables run from the inverter to any outlets intended to power appliances needing AC current, generally things like hair dryers or toasters in larger recreational vehicles. AC cables also connect the inverter to the circuit breakers and the fuse box. In-home solar systems AC cables are used to connect to the grid.
Adapters, Connectors and Lugs
In an outdoor solar setup, like that in an RV or campervan, all components need to be connected with the appropriate current loading and cable. There are various kinds of connectors, with the most notable being MC4 connectors. Connectors fuse to the cable by way of crimpled couplers, preferably of the same materials and thickness as the wire. Paired cables with Anderson adapters are used to connect the solar charge controllers to batteries or the panels. Tinned copper lug terminal rings are found at the ends connecting to the battery poles.
Buying Solar Cables and Wires
Solar cables and wires are sold through distributors of solar equipment and systems throughout Australia. A retail salesperson will inform you of the types of wires, cables and connectors needed for your particular solar setup.