affer wrote: ↑
Thu, 05 Sep 2019, 21:08
i exceeded the specs on the mk (150VoC) and above 115 MPPT, then i saw a lot of dips, now i am back to 3x40VoC and apprx 92-ish MPPT, now everything is back to normal
Well, I thought excessive PV voltage was one of the first things suggested. Sorry, I should have noticed the PV voltage peaks in the graph above almost touching the 150 V line on the graph. Too many panels in series would explain the dips perfectly: as soon as PV panel power decreases near the middle of the day (because the battery is charged, or nearly so, and the loads happen to be low), then the panel voltage will rise. As soon as it hits 130 V, the MPPT derates itself, reducing the load further, increasing the panel voltage further, and you get a kind of positive feedback situation, ending up with no load on the panels. To get started from that point, you need enough shade to bring the panel voltage below 145 V; the MPPT (which now needs some PV power to recharge the battery) will then start using some panel power, which will reduce the panel voltage, and as it heads to 130 V, it stops derating altogether (the MPPT can use all it wants), and while there is enough load, the system will be normal. But next dip in the load will trigger another dip in the PV power. By late afternoon, there isn't enough insolation from the sun to cause the positive feedback situation, and the dips stop happening. In between middday and late afternoon, the frequency of dips decreases.
Derating is what the solar controller (commonly called the MPPT) does when it gets too hot, or the panel voltage becomes too high. Usually, it just reduces power according to a straight line graph, e.g. max 100% power at 130 V, 67% at 135 V, 33% at 140 V, and 0% (no power) at 145 V or above. Above 145 V there is the possibility of damaging the electronics (e.g. drying out the capacitors, avalanche breakdown of the MOSFETs). Similarly, it might start imposing lower and lower power limits above say 85 °C, reducing to zero power at say 100 °C. By running with reduced power or no power at all (not switching the MOSFETs) reduces the likelihood of damaging the hardware.
So yes, 3S x 2P or 3P (of 60 cell panels) would solve the problem. If they are 72-cell panels, then you'll probably have dips in winter, because cold panels have higher voltage.
Are others running say 3S of 72-cell panels on their PIP-5048MKs / Axpert Kings?
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.