520w 24v Solar system drop voltage on short circuit

[mnsdall]

Hi guyes ,
I hope you doing very well.
I recently install 4 130w (12v) solar panels connected in 2,2 in parallel so it's as a 24v system (panel specification in Image sorry its not very clear
//www.diynot.com/network/mnsdall/albums )
And I'm using 30A PWM charge controller.
The problem is when I connect my battery bank(600ah Gel amg batteries)
And in full sunshine 45C' it's voltage drop and only I get 25.8 v max.
But open circuit v is fine approx 35v
I'm using 16mm2 single core cable.
Can any one help me to solving this problem.
Thanks a lot.

 

[bernardgreen]

Most probably the voltage drop is due to the internal resistance of the solar panels. Even though they create electrical power their internal paths for the current have resistance across which there will be a voltage drop when current flows from the solar panel.