RV Solar Wire Size
Wire sizes are opposite of what you would think. The smaller the number the bigger the diameter of the wire. In a solar installation 10awg is common PV wire. For higher current (amps) you may go larger, for example 8awg. Wire size is based on the maximum amps a wire is expected to see. If you undersized a wire, then the wire could overheat or even catch fire. If you choose too large, you add weight, cost, and space unnecessarily. The best place to start in calculating maximum amps is with the solar panels. Assuming you want to use standard 10awg PV wire, organize your solar array such that the max current will be no more than 30 amps. You accomplish this arranging solar panels in series and/or parallel. I suggest using similar solar panels in an installation rather than mixing and matching. Look at the sticker on the back of the solar panel. It will provide max current and voltage ( I would be conservative and use VOC rather than VRM). When putting panels in series, add the voltage and amps stay the same; when adding panels in parallel, add amps and voltage stays the same. For example, 2p3s would have 2 parallel rows of 3 solar panels connected in series. The benefit of going with higher voltage is keeping the wire size small, the detriment is having too high voltage for the solar charger and panels in series do not handle shading well. Common wire sizes are 10,8,6,4,2,1, 1/0,2/0,3/0,4/0,300mcm,350mcm.
Stranded wire is typical for solar installations. Stranded provides the most flexibility for passing wires through tight spots. Additionally, mobile applications may experience fatigue when using solid wire. If you buy wire on Amazon or EBay, you may be tempted to buy the cheapest, don’t do it. It is likely called “copper clad” wire. It is aluminum wire with copper outer shell. I recommend pure copper. Also get good quality rubber insulation often referred to as battery or welding wire. You should be able to easily roll it up in a small circle. Yes, good quality large diameter battery cable is expensive.
Crimping is the common method for making connections. Larger wires may use battery lugs that you find in auto parts stores. Usually a shrink wrap sleeve is put on the connection using a heat gun. Where a screw is used to tighten down a wire it I’d highly recommended to use a feral to combine all wire strands together. We have seen instances where a stray strand causes a short. Loose connecting wires are a common source of fires so tighten down all connections and use an automotive automatic fire extinguisher for more protection.