I recently bought three 425-watt solar panels with a VOC of 38.74V and ISC of 13.46A each. The MPPT controller I have can handle a maximum PV input of 100V DC and 60A. When I try to figure out how to connect these panels, it seems like connecting them in series exceeds the voltage limit, while connecting them in parallel goes over the fuse amperage. This has me thinking that my only choice might be to use just two panels or invest in a better MPPT controller. Am I overlooking another possible solution?
3 Answers
You mentioned the max series fuse rating for each string, so keep that in mind. One option you have is to add a fourth panel and go with a 2s2p configuration (two strings of two panels each). This can help you distribute the load better. Just a heads up though, if you're using a 12V battery system, having only two panels may already be pushing your limits. Even with four panels, you might hit some overpaneling unless you're on a 24V battery system or higher.
Some MPPT controllers can handle higher amp inputs safely; they just won't utilize anything above their rated amperage. However, regarding higher voltages, I don't think there's any controller out there that supports going over the rated input voltage. Also, remember that colder temperatures can actually increase panel voltage output during charging, so factor that in when planning your setup.
Another idea would be to keep using your two panels in series with your current MPPT and grab a smaller MPPT to run the third panel by itself. Sure, it involves a bit more wiring, but this setup could give you more flexibility without breaking the bank.