Qfyilyi

In the effort of saving money without having to buy expensive solar cables (and because I have a lot of extra coax cable lying around doing nothing), I would like to use a piece of coax cable (that looks like antenna cable), to transfer 54V and up to 5A of solar power into the house. The length would be no more than about 20 feet and can be made even shorter. This is a very small solar application to charge a small 48V battery bank. If I do not know the type of cable (such as RG-6) so that I cannot just look up the specs on it, generally speaking, is it fairly safe to assume just about ANY piece of coax normally used for cable TV or antennas can handle 54V and 5A? I think it is reasonable. Note that I would not use the end "F" connectors, I would use stripped ends to attach to the solar panel cables and somehow weatherproof them, and on the charger (indoor) side, also stripped ends.

I should mention that the near 5A flow would only be in certain conditions (like when the battery bank is in a mid state of charge and there is full sun directly over the panels). I would say on average, the current flow should be more like 2.5A to 3A.

I think the 1/4 inch (or so) coax cables (RG59, RG6 etc.) would have too small a center conductor to safely carry 5 Amp, The 0.4 inch cables (RG8 or RG11) should be OK for 5 Amp.

Most coax has a type or part number laser-markes onto the outer jacket at periodic intervals. If not, measure the diameter of the inner conductor and convert to an equivalent AWG. You could also pass 5A through a sample piece in an environment representative of your worst-case thermal situation (e.g. when it's going through a thermally insulating feedthrough) for ~30 mins and see if there's an appreciable temperature rise.

No, you can "not" assume that any "random" coaxial cable can "reliably" carry 5A. Determine what kind of cable you have, then look up its specifications.