Planning on using 4mm is it correct?

[goneoff]

I’m planning fitting 2 x 120w solar panels connected in series on our Laika; the run to the controller will be circa 4.5m and from controller to batteries circa 1.5m was planning using 4mm stranded will this be OK or am I over engineering it? Thanks

 

[Off da Grid]

I think you will find the cabling from the panels themselves is 4mm, I seem to remember that 12v planet do 4mm extension cables for solar.
I think I used 6mm though for mine.

 

[Metamorfosis]

I am no expert but have installed before and been reading every resource available this last week and received some sage advice too as I have an imminent install myself. In the past I have been guilty of over analysing and over engineering things. My conclusion is that there are so many variables that reduce the efficiency of the solar array it isn't worth worrying about it, or creating more work than necessary. Bird crap on a panel will likely reduce your wattage far more than any run length or cable thickness considerations. A lot of forum advice in the past has been to try and eek as much power out of a single small panel, with poor pwm controllers and restricted old electroblocks. Solar is cheap nowadays and interfaces are much more capable so if you have 4mm prewiring in place then use it. Just whack in the biggest pair of affordable panels you can and accept there are some losses.

 

[Silver-Fox]

There’s a lot of info on here regarding solar installs.
Might take a bit of digging out

I used 6 mm from the panels to the controller less resistant and all that technical stuff

 

[Lenny HB]

4mm will be fine, the greatest volt drop over the cable will be in summer when the panels are producing plenty of power. In the winter when the panel aren't producing much power the volt drop will be insignificant.
You might want to reconsider wiring them in series, although slightly more efficient shade on one panel you will lose the output from both. Parallel is prefered on Motorhomes so if one panel is in shade you still get the output from the other panel.

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[The Wino]

I think I over thought mine. The instructions said to put the solar controller as close as possible to the battery presumably as the panel voltage is higher than that to the battery but as it was only a single 100w panel with 2.5mm cable and the prewired cable was 4mm I figured the difference in loss was minimal and as we have managed 5 years with nothing either would work.