Advice on DC to DC wire run for popup camper and Renogy DCC50S

[sunshine]

It's just the positive line though.

I agree with the others that think this is a bad idea.
Include the negative with twin cable and a twin connector that disconnects both at the same time.
Not sure of your towing hitch but even steel towing balls are not a reliable return connection and you don't want the return path suddenly going back through a very thin wire.

 

[F1uxCapacitor]

Just came across this and thought it may help

 

[brooke_heaton]

Thanks for sharing that @F1uxCapacitor. I came across that video and the comments helped me wrap my head around the 'common ground' connected to the chassis. Thinking about it more, I may have situations where I won't have my tow vehicle hooked up to the trailer, but may want to plug in the DC-to-DC power. This made me rethink the logic of that and I think I'll run a negative line between the charger and the tow vehicle battery. Better safe than sorry and better to do it right the first time than to have to redo everything. Renogy recommends 4 AWG for a 30 ft length, so I'm going o go out and try to get a more accurate estimate of how long my run is. I'm likely to do 2 AWG. So all things told, this project just got twice as expensive :/ oh well.

 

[brooke_heaton]

@sunshine I've decided to go with both pos and neg cables. I realize now that other systems may have bigger chassis or a different setup. I don't think the common ground to chassis will work unless my popup is connected via the hitch to the TV and I think two cables will be a more trustworthy approach. I plan to use 2 AWG pure copper cables for the run.

 

[sunshine]

I plan to use 2 AWG pure copper cables for the run.

Maybe best to to feel the cable for stiffness before buying. 2AWG maybe too thick and not be suitable. We use metric, mm2, and even then where I buy cable from the imported wire never seems to correspond to standard sizes.
Considering I would go for 8mmsq from BigWei, and this seems to convert to 8AWG in your measurements the difference is considerable and maybe needs better clarification from someone who knows their cables!

I use 10mm2 cable over 15m and 62amps.