Serial vs Parallel Solar Panel Shading

liborko wrote:
The PWM controller does not operate at Isc. Isc is a short circuit current with zero volts on panel's terminals. What PWM controller does is switching the current on and off at BATTERY voltage once it starts controlling. Since solar panels are rated at their Maximum Power Point, only MPPT controller extracts panel's rated power because it operates at Maximum Power Point and not battery voltage which is lower.
With panels in parallel only panels in shade are affected. With panels in series you have to rely on bypass diodes to get any output which is not what I am prepared to do.
How MPPT controller works depends entirely on the manufacturer of the controller and we all know that there is abundance of bogus claims.

You seem to never have actually measured anything in the field. Try it.

The PWM controller passes amps to the battery at the same value as taking the Isc at that time with the panel disconnected. So I talk as though the batteries receive Isc amps as per the panel rating.

You can go blue in the face saying you can't get Isc because that is when the panel is shorted. Fill your boots. :)

The fact is you can check your panel Isc with the panel disconnected at any time and reconnect and you will see the same amps as the Isc you just got going to the battery. Of course most of the day the Isc is less than rated due to sun conditions at the time. other times it is over the rated Isc. Whatever it is at, that's the amps to the battery.

Express that however you wish.

And note that Isc goes up with panel heating, not down like its voltage, so with the MPPT using watts, which has the voltage as the major component, it loses watts, while the PWM using amps does not lose anything. This is how they come out near equal for amps to the battery.

And it is ludicrous to even mention Vmp for a panel when using PWM. That immediately shows an ignorance of what happens with solar. :( It is not about the watts; it is about the amps.

For example, my 130w 12v panel rated at 8.2a Isc and 21.9v Voc in full sun would measure 20.2 Voc (panel heating reduction!) and 8.2 or 8.3 Isc. On battery it would then show 8.2 or 8.3a on the Timetric going to the battery. That is how PWM works. You get "Isc amps" to the battery.

With MPPT amps to the battery you get output watts/battery voltage, and the output watts is way less than the panel rated watts. Get used to it :(