Serial vs Parallel Solar Panel Shading
I was asked if a post in another thread if this "Serial is actually better for shading (than parallel) if that is a concern for you." was a typo. It is not a typo but panel shading is not always under...
Forum Discussion
The series mppt verus parallel pwm is not cut and dry
It's not just math either
There is a bit of 'either-or' digital style logic involved
Not because of digital chips
But because of solid state devices either adding output, or passing output thru
Example three 20v 5 amp 100 Watt panels in parallel
20v 15 amps, if one panel is shaded it's 20v 10 amps
Same three panels in series 60v 5 amps, if one panel is shaded it becomes 40v at 5 amps, minus tiny losses in bypass diodes of the shaded panel, that is passing the amps from the other two unshaded panels
The previous drawings provided by the OP showed partial shading on one string of cells in one panel, allowing partial power from that panel
What he did not show was the effects was partial shade across the width of the panel shading a few cells in all strings, totally shutting down that panel
Which is what i am referencing in this statement
A series string with possibly lighter guage wire, might be easier to install, but does the extras cost of the mppt controller warrant the minor gains of ease of install
Over the cost of more connections involved with pwm controller
In an RV install verus fixed location
I think the advantage goes to the controller with most adjustments, the controller that offers the most user changeable settings
At the least cost, in other words the system that is the most configurable verus dollar cost
Certainly if you are grid tie, then high voltage series panel system is a plus
If you are running a 48v power system , then again series and mppt is a plus factor
But for 12v RV install, IMO, high voltage series install, does not present significant gains compared to cost, not for small systems
Now if you cover the roof and get 1200w or more and the panel pricing is low enough to offset the controller price, it becomes a different set of values
It's not just math either
There is a bit of 'either-or' digital style logic involved
Not because of digital chips
But because of solid state devices either adding output, or passing output thru
Example three 20v 5 amp 100 Watt panels in parallel
20v 15 amps, if one panel is shaded it's 20v 10 amps
Same three panels in series 60v 5 amps, if one panel is shaded it becomes 40v at 5 amps, minus tiny losses in bypass diodes of the shaded panel, that is passing the amps from the other two unshaded panels
The previous drawings provided by the OP showed partial shading on one string of cells in one panel, allowing partial power from that panel
What he did not show was the effects was partial shade across the width of the panel shading a few cells in all strings, totally shutting down that panel
Which is what i am referencing in this statement
A series string with possibly lighter guage wire, might be easier to install, but does the extras cost of the mppt controller warrant the minor gains of ease of install
Over the cost of more connections involved with pwm controller
In an RV install verus fixed location
I think the advantage goes to the controller with most adjustments, the controller that offers the most user changeable settings
At the least cost, in other words the system that is the most configurable verus dollar cost
Certainly if you are grid tie, then high voltage series panel system is a plus
If you are running a 48v power system , then again series and mppt is a plus factor
But for 12v RV install, IMO, high voltage series install, does not present significant gains compared to cost, not for small systems
Now if you cover the roof and get 1200w or more and the panel pricing is low enough to offset the controller price, it becomes a different set of values
