Hello all,
i have seen some discussions regarding parallel strings in different orientation.
My question is:
Is it possible to exceed MMPT Watt rating if not exceeding the open Voltage?
So i currently have a 100|20 MPPT operating at 48v and purchased 12 second hand 280w Panels.
I have calculated i can connect 2s2p and not exceed Voltage/Wattage.
with that in mind, is it possible to do 2s4p with each group of 4 panels in a different orientation, without frying the MPPT?
pre-Thanks!
Chen.
Your main concern is to not exceed the 100V PV Voltage limit. You can connect 2 modules in series to stay under this limit.
Yes, you can exceed the power rating. The maximum nominal power that this MPPT can produce in a 48V system is 960W, (+1000W realistic maximum as battery Voltage is over 50V). If you have more PV power then it is not a problem, the MPPT will continue to produce the maximum power and no more. You have quite a few more panels than this MPPT can make use of, but in overcast weather your 3.4KW array will likely still be able to produce 1000W.
Hi wkirby, Thanks!
Indeed my systems top Voltage is 56.8 Lifepo4 16S limiting top charge voltage per battery to 3.55
From what i can see in the spec sheet of the MPPT it is capable of 1160W at 48v, what is the best case scenario to reach the maximum wattage?
i'm currently in the research phase of building my solar, and my previous assumption is that i would need 2x 250|100 MPPT's for 40x280w, but now thinking maybe just one will suffice, also (typing as i think, maybe 2x 150|70 would be the wiser choice for redundancy, assuming that the lower voltage would not require larger more expensive cables.
Hi @chenirl
It's not Wattage that's the issue, but the 'Max PV short circuit current'. and that mppt is specced at 20 Amps on the pv side.
If you look at the Isc rating of the panels, that might be say ~8A, so to have more than 2 strings would exceed the 20A. The mppt specsheet warns of this, so to exceed it is at your own risk..
I'm Confused.
At the end of the table it states:
1a) If more PV power is connected , the controller will limit the input power.
2) A PV array with a higher short circuit current may damage the controller.
My Solar Panel's Short Circuit Current-ISC (A)8.33
So to try to sum it up:
1. My understanig is that current is a matter of "Pulling" from the panel.
2. What would be the condition that would "reach" the "Panel Short Circuit Current" rating?
Industry "Best Practice" does not recommend connecting sub arrays with different orientation (>5 degrees) to the same tracker. If you do this, then you have to be very careful to compute the maximum power from the combined arrays. Exceeding the Max input current of the tracker can cause damage, as when searching for the Max power spot, higher than normal operating currents can be drawn.
