oughtsix wrote:
...Everything I have read says that the solar controller should be put as close as possible to the solar panels. So you put the solar controller in the cabinet then breach the roof to run wires to the solar panels. I have also read that even a partial shadow on a single panel can greatly reduce the output of a bank of panels.
The solar controller should be installed as close to the
batteries as possible in order to minimize voltage drop on the charging line. The distance between the panels and the controller is not as critical because "12V" panels are usually over 17V when at full power and any voltage drop experienced between the panels and controller still allows for voltage in excess of the desired charging voltage.
It is true that even a small amount of shade on a panel can shut down that panel's output. But a bank of panels can be wired in parallel and the panels in the other parallel paths wouldn't be impacted if they are unshaded. Panels wired in series would be, though. Having to park in the unobstructed sun is a requirement for good solar harvest.
This solar ready setup provides convenient pre-wired access to the roof but the proposed controller location is far from ideal. With 8 gauge wiring and a 20' wire run from controller to the batteries, a hypothetical 140 watt panel providing 8 amps at max output (using my panels for this hypothetical) would experience a 0.2 V drop. So if your controller is putting out 14.4V, the batteries would only see 14.2V. I would suggest a solar charge controller with programmable setpoints so you can compensate for the voltage drop (set the setpoints 0.2V higher so the batteries will get the desired voltage).
Voltage drop calculator
