In case when one or more solar panels are affected either by shading or by other damage caused during the manufacture or along the life cycle of the system the performance of other solar panels in the array is not affected because the wiring connection makes every single unit independent from the other one.
Connecting two arrays of solar panels.
If we have two solar panels with the same voltage but different wattage there is no problem.
The rule of thumb when connecting solar panels directly to a battery is never connect more than c 10 watts where c is the capacity of your battery.
Stringing solar panels in series involves connecting each panel to the next in a line as illustrated in the left side of the diagram above.
The main advantage of this configuration is reliability.
For example a 110ah battery should never be connected to a panel more than 11w without a solar controller and if you are using a solar controller you do not need a blocking diode.
Connecting solar panels in series.
Connecting in series means joining the positive terminal of a solar panel to the negative terminal of the next solar panel until eventually you are left with one free positive and one free negative terminal of the array which are to be connected to the input either of the inverter in case of a grid tied system without a battery backup or the charge controller in case of a grid tied system.
They can be wired in parallel.
On the other hand if our two solar panels have both different wattage and different voltage then parallel connection is not possible since the panel with the lowest voltage would behave like a load and would begin to absorb current instead of producing it with the.