I'm finalizing my solar system setup and have a specific question regarding the effect of overpaneling on my inverter's maximum power point tracking (MPPT). My roof design allows for 27 panels divided across two arrays: Array 1 has one string of 9 panels connected to one MPPT, and Array 2 has two strings of 9 panels to another MPPT. I used to use the FlexBoss21, but I'm switching to the FlexBoss18, which has a lower amp limit that might complicate things.
To give you some context, I'm using APTOS 410W panels (Voc: 37.32V, Isc: 13.95A) with the FlexBoss18 (MPPT Vmax: 600V, MPPT Imax: 26A). Here's my math for the combined strings:
* Current: 13.95A (Isc) x 2 strings = 27.9A (which is over the 26A limit for MPPT1)
* Voltage: 37.32V (Voc) x 9 panels = 335.88V (which is under the 600V max)
* Wattage: Total system wattage is 27 panels x 410W = 11,070W (which is under the inverter's 18kW rating)
My main question is about the consequences of exceeding the MPPT's amp limit. Will it simply lead to performance losses where the inverter caps at 26A, or could it stress components and risk potential damage?
2 Answers
You're comparing the Isc rating of the panels to the max working amperage of the MPPT rather than the max Isc it can handle. If your panel's output current (Imp) is less than 26A, you should be fine, since clipping usually only happens at peak output. Everything looks like it's within spec, so unlikely that you'd face amp clipping as long as you keep Imp below the inverter's limits.
It's a good idea to check with the manufacturer directly about how much you can exceed the amperage safely. From my understanding, while the max allowed is around 31A and the MPPT can use 26A, it's best to verify with them for your specific inverter.
Perfect - that's exactly the clarity I needed. Thanks!