Solar panels - cables specification etc

[Leopold_Stuff]

Hi, what is your suggestion regarding cable diameter for 2 panels 100W each? Everywhere I see 4mm but it seems to be quite thick. Isn't 2,5 enough?

What about UV/weather protection? Is that necessary? I'm trying to find a curly cable that fulfill those requirements but without any success.

How do you connect 2 panels? Parallel or in series? I found that parallel system is more efficient when one of the panels is in the shade but on the other hand connection in series gives you more V, so in the lower light it keeps charging the battery. What is you opinion?

 

[scottk]

There is a solar power section in one of the sub forums. One of the guys on the forum is Roger Donaghue of Solar Camper Solutions. He would be a good source of info. I don’t know if he sells his kits to Poland due to the VAT restrictions though.

Solar Panels

vwcaliforniaclub.com

 

[yossarian]

Hi, what is your suggestion regarding cable diameter for 2 panels 100W each? Everywhere I see 4mm but it seems to be quite thick. Isn't 2,5 enough?

100W at 18V will give you around 6A. 2.5mm cable should be good for 20A.

Worst case is panels in parallel with around 12A. I think 2.5mm should be fine in any scenario.

I suspect Roger supplies cables etc speced for his worst case which is 300W+

How do you connect 2 panels? Parallel or in series? I found that parallel system is more efficient when one of the panels is in the shade but on the other hand connection in series gives you more V, so in the lower light it keeps charging the battery. What is you opinion?

My opinion is: connect in series unless you have a PWM controller or some other good reason to connect in parallel. Check the specs of your controller and allow some head room over open circuit voltage of your panels.

 

[yossarian]

Cable Size Calculator - Cable sizing and selection | 12 Volt Planet

Cable Size Calculator - Read our guide to selecting cable of the correct type and size for your automotive, marine or leisure wiring application. Auto and Marine Electrical Components from 12 Volt Planet

www.12voltplanet.co.uk

Their voltage drop and loss calculation is useful. I get about 3% in parallel and under 1% in series.

 

[Leopold_Stuff]

Thanks for your help. It's very useful!