Sizing tool when using combinations of panels

[Govette]

Hi guys,
1st post, and complete novice so please excuse me if I make some fundimental mistakes.
I currently have 7 BP 140W panels running in parallel (through an older PL40 controller). I'd like to break them down into 2 packets of 3 panels in series for a push of 72V (leaving 1 panel spare), and then add 2 packets of 3 Sino Silicon 250W, to end up with 2340W total. Is it possible to do this through one 150V Classic, ie are you able to put two different sized panel types through the same controller? Alternatively, I also have a couple extra BP 140W panels running a water-pump which I could perhaps replace with a single 250W, thus giving  me a 3rd packet of 140W. This would give a total of 2760W, which if I am reading it correctly is slightly more than the 150V Classic is rated for. Is there a classic that can control that amount, or would I then be up for running multiples.
Any advice and/ or guidance is much welcomed. Cheers, have a great day.
Gov

[Kent0]

You need to specify which Sino Silicon 250-watt module you are considering. There is one with 96 5-inch cells and Vmp = 49.7 volts and another with 60 6-inch cells and Vmp = 30 volts. The BP 140-watt panel has 72 cells with Vmp = 34 volts.

Putting three of the BP modules in series gives 216 cells in series and Vmp = 102 volts. Two of the Sino Silicon 96-cell modules in series is 192 cells and Vmp = 99.4 volts. That shouldn't be too bad of a match. But if you are considering the 60-cell Sino Silicon modules three of them in series would be 180 cells and Vmp =90 volts, not a very good match for the BP 140s.

[Govette]

Hi Kent0, thanks very much for replying so quickly and for the info. Yes, the Sino Silicon's are the 96 cell one. Any chance you could expand as to why that is important and what 'not too bad' a match means?? I'm very keen to learn the why's as well as the what's....
Cheers

[Kent0]

If the Vmp is an exact match then all the parallel strings are at maximum power at the same voltage. If there is a mismatch in the Vmp voltages, the maximum power from the system is less than you'd get by adding up the power that's available from all of the strings. If the voltage is different by 5%, then the power loss is probably in the 2 percent range. In general, the power loss, in percent, is probably less than one-half of of voltage mismatch in percent. At 5% voltage mismatch you are talking about power losses that are probably as much as you'd consider acceptable for the wiring. But there is a significant difference - at 50% irradiance the wire losses will drop by 50%, losses because of Vmp mismatch won't drop significantly.

[Govette]

Ahhhh, I see. Cool, thanks very much for that. So, looking at the panel specs I see that the BP140's are Vmp of 34v so a string of three is 102v, as you said. However the specs for the Sino state 50.78v so two of them is 101.56. That's less than 1% so kinda .... ummm, bugger all really huh!!! Thanks so much for explaining that, much appreciated. Have a great day,
Cheers