Jaco Venter wrote: ↑
Did a test over the weekend by connecting 2 panels in series and 6 strings.
Started up with that on Saturday morning and even before 08:00 the PV Watts dipped 4 times. I then changed it back to 3 panels in series and 5 strings.
Ok, that sounds pretty convincing that it's not OCV. In your graphs below, it only comes to 124 V, which should be fine.
What I also found is that if the PV Watts freeze up, I only need to switch of the DC feed from the panels to the inverter. After switching the DC feed on again the inverter start using the PV power again.
The Solar Charge Controller operates only from PV power. So that means that resetting the SCC, and not
the main DSP (processor), is enough to get things running again. That suggests that the problem lies with the SCC firmware, rather than the DSP firmware. Or maybe it's something that the DSP does (sends to the SCC?) that causes the SCC to crash, and resetting the SCC lets it start again.
Something strange for me, and hopefully you can explain, is that when I switch the PV Infeed to the inverter off the PV volts on the inverter only drop from 124V to about 50V. I expected it to drop to 0V. Is there internal caps inside the inverter keeping some Volts or???
That's because the main SCC MOSFETs have integral back diodes, so the PV input can't be less positive than the battery voltage, less one power diode drop (about 0.3 to 0.5 V). The reason it sometimes reports
as zero volts is because the SCC isn't running, so there are no reports of SCC current to the DSP, so it assumes zero. There must be large capacitors in the SCC, as you suggested, keeping the SCC processor alive for a minute or so after PV input is removed. And/or the main processor hasn't given up on the SCC just yet, and is using the last PV voltage value that was sent some time ago.
Today it freezed when the batteries reached point where the system needed to change to Solar/Battery. THe moment it change fron Utility to Solar it ran for a while on Utility @ 165 Watts and the Solar supplied the load and the batteries. Almost if the Utility did not want to part from Battery charging as it is set to charge at 2Amps while Utility is on.
Huh. The PIP-5048MKs/Kings have a separate AC to DC converter. There might be large capacitors in that circuit that allows a little extra power to come through even though officially it's turned off.
Some recommendations I received include the option to add an additional King in parallel. (Not to sure if it will solve my (or the Inverter) problem.
Maybe they're trying to move some old stock with known-bad firmware :-O I can't see how that would help.
Just a thought: do the dips coincide with clouds? On my system with plenty of panel power, a mild cloud will dip to 25% of max power, but a dark cloud will dip output to 10% of max power. You seem to have maximum charge current set to 20 A (I'm guessing one Pylontech US2000 or similar?), and 10% of 20 A is just 2 A. Maybe the SCC freaks out and decides that such a low current means it's night time and it's time to shut down. But really you have some 3 kW of available panel power a lot of the time, so it would dip to only around 300 W with dark clouds, which is still 5 A @ 50 V. But it would explain why dips are worst away from noon (when your 3 kW is more like 1.5 - 2 kW).
I wonder if it explains the freezes as well. Maybe a dip to very low PV charge current is treated as twilight: turn off output, and wait for real sunset. A longer dark cloud might convince it that it really is sunset, so actually turn off. But surely when the dark cloud passes, the SCC should start again (oh, it's sunrise already!). So it's a desperate thought.
Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.