My question is why do you want to do it this way?
Good question.
2 reasons.
1. To broaden my knowledge and understanding
2. my personal circumstance.....
I have a 5.7kW system ( 5.7 PV and 5kw dual MPPT inverter)
My system is now 8 years old.
I have 2 strings.
String one is 2 strings of 10 panels in parallel, all grouped together and facing north.
String two is 1 string of 11 panels, grouped together, facing east.
There is no spare roof space available north or east.
I would like to drive the inverter a bit harder and flatten out my daily production bell curve. (and increase my daily output)
My daily production is biased to late-morning due to the east facing string. Power production generally peaks around 11am and then tapers off as the east facing string gets less and less direct sunlight.
So the obvious solution is to add panels onto the west facing roof, and parallel them onto the second MPPT ( with the east string = 11 panels )
The current "advice" is that this can be done is using the exact same panels and number of panels. (( i.e. 11 panels the same as what I have (suntech 195W ))
The issue is that these panels are not available any more, and I still think that blocking diodes will be required to prevent reverse biasing the cells if there was any shadowing.
So, my options are to replace ALL of the panels, so that the 2 paralleled east and west facing strings are exactly the same
OR
just create a second string that is near enough to the OCV of the existing string of 11, add a couple of dollars worth of blocking diodes and BAM, I will have string #2 (east west) producing ~2kWh for nearly the whole day, instead of peaking at 11am and then tapering off to not much by mid-arvo.
Hope that makes sense.