Our welding cables at work are always exposed to the elements. They last for years of abuse and negligence. The ends connection is our only problem. 

I had a set of jumpers made from welding cable. The insulation split and had to be repaired many times. I'm sure there are better grades of welding cable, but I don't know how to pick the better ones. All I'm saying is marine grade made in usa is the best choice for me. I do know that it will be the best quality. GDZ delivers in one or two days from ordering. Solar panel leads, with MC4 ends, is from Windy Nation solar supply.

  FWIW Over many years I have experienced the same satisfaction as Glenn above when it comes to "welding cable". While a past used equipment dealer and farmer I came across a ton of welding cable and it generally speaking had good quality tough high abrasive resistant jacket/insulation as it got dragged down gravel or blacktop driveways up over and around all sorts of sharp steel or machinery and sharp bends plus often sat outside on a welding truck exposed to sun rain wind snow n drastic temperature changes grrrrrrrrrrrrrr it better be tough and good quality to withstand all that lol

 Of course, there are different grades and brands and quality, some maybe poor some maybe excellent, some cheap some expensive, but I may have lucked out as that which I came across happen to be great quality and endurability while some others may have  observed poor quality...….That comes as no surprise to me as there are a ton of manufacturers and grades out there.

 Unfortunately absent deep research I don't know how to tell what types or brands or specs or codes or ratings are good or bad for any specific application, so I wouldn't make any recommendations in the dark. DO YOUR HOMEWORK

 As far as any "Solar" wiring rating (UL or NEC or RVIA etc) a panel is a DC energy source such as a battery or charger etc etc so if a person were choosing so called  "Marine Grade"  or some sort of so called "Solar Grade" one thing I see as critical is the environment so if the wire is ran on an RV rooftop exposed to sun, rain and temp changes and regardless if the energy source were a charger or solar panel you need good ultraviolet protection as well as other element protection including flexibility and vibration resistance.

 Marine Grade, Solar Rated, Welding Cable, UL, NEC, RVIA, may all have a role in decision making. Do your research and make your choice that's best for YOU...……….

   Best wishes yall, very fun and interesting thread for us sparkies at least lol

 John T

Ok, so marine grade cable makes sense in the environment our RVs are subjected to....

Most marine grade cable is tinned copper. It it really “tin” or is it solder?

does this coating have an negative effect as it pertains to voltage loss?

Found my answer.....From now on, marine grade tinned wire will be all I’ll https://www.pacergroup.net/pacer-news/tinned-copper-vs-bare-copper/

Don’t the little electrons “flow” down the outside of the wire kinda? Therefore many strands are better for low voltage pressures? 

Or did I read false news somewhere?

  On 10/28/2019 at 4:31 AM, noteven said:

Don’t the little electrons “flow” down the outside of the wire kinda? Therefore many strands are better for low voltage pressures? 

Or did I read false news somewhere?

Generally agreed upon. 

ETA: Also helps with flexibility. 

Edited October 28 by Darryl&Rita

  On 10/28/2019 at 4:31 AM, noteven said:

Don’t the little electrons “flow” down the outside of the wire kinda? Therefore many strands are better for low voltage pressures? 

Or did I read false news somewhere?

I believe that this is correct only for A/C current at high voltages. For our DC systems in the 12V - 48V range there is no so-called "skin effect".  However, lots of small wires does make for good flexibility, so there is that...

Found this...

”alternating current produces alternating magnetic flux inside and around the conductor. ... this effect is more at the center of conductor. so electrons tend to flow through surface. In DC there will not be any alternating magnetic field and so no Skin effect is not observed”

  rb, as I best recall (NO Warranty) the so called "skin effect" was only of major concern when talking high frequency and NOT in DC circuits. You're only talking about a 25 ft DC run OUTSIDE an RV FROM a portable energy source TO an external Outlet/Plug (or other connection method) at (if 17 Vmp at 120 watts) 7 Amps DC max, so I think 40 Amp rated wire (such as #8 Copper or other 40 Amp rated equivalent) be it some sort of so called "Marine Grade",  be it some sort of so called "Solar Rated" or be it some sort of so called "Welding Cable" will  "WORK" satisfactory. NOTE, I'm NOT saying the grades or ratings or any UL or NEC or RVIA approved wire (to the extent any such exist or are even applicable) shouldn't be considered and its best to reduce line voltage drop as much as one can, I'm ONLY saying ANY of such conductors approved for exterior and wet locations with ultraviolet protection and 40 Amp rated is a decent choice and I wouldn't loose much sleep overthinking or worrying too much beyond that.

CONGRATULATIONS you ask good questions and are doing research so you should end up with a good product. 

John T