Hi,

I open new topic about how is charging inverter battery becouse i receive to repair many inverters with error F08 (Bus voltage too high). I not pay more attention until now to charger, only to mppt BUT this is not charger efective to inverters, this only get BUS voltage and some low power 48V . I not see any power source to cgarge battery, and i think charger is revers to inverter from BUS voltage to battery voltage from grid and solar, except old inverters with mppt low voltage and PWM. I am wrong?

I want to know why receive F08 error when i charge from grid, what is wrong? problem is hardware or software.

7 minutes ago, mihaigsm2003 said:

i think charger is revers to inverter from BUS voltage to battery voltage from grid and solar, except old inverters with mppt low voltage

For 5 kW models and above, the block diagram is:

So for the 450-500 V max PV models (green paths, not blue paths), PV voltage is boosted to bus voltage, then pushed right to left in the diagram above through the buck converter and DC-DC converter. The buck converter is what regulates battery charging current (PV or utility). All utility charging (only for non-King 5 kW models and above) is by pushing power backwards from the AC-out (connected to AC-in via the left switch) to the DC bus via the full bridge (DC↔AC converter).

13 minutes ago, mihaigsm2003 said:

I want to know why receive F08 error when i charge from grid, what is wrong?

My belief is that most of this is due to leakage from PV terminals to earth. The high PV voltage Solar Charge Controllers are referenced to the negative side of the DC bus, since the output is the DC bus itself. This has high potentials with respect to earth, because the neutral output is at basically earth potential, and so earth is connected alternately to the negative end of  the DC bus or to the positive end. That means that the PV terminals have hundreds of volts with respect to earth half the time, and currents from earth into the neutral output of the full bridge can push up the bus voltage (I think). I haven't sat down and proven it to myself, but it seems likely.

This increase in bus voltage is not under firmware control, so it can ramp up over seconds or minutes to exceed the safe level, and fault code F08 results.

PV panel frames have to be earthed, especially in South Africa where there is a lot of lightning activity, and rain in conjunction with bad wiring practices and/or cheap panels can cause leakage to earth. I believe that Voltronic in their user manuals actually warn that only certain types of PV panel should be used with these high voltage PV models, or the frames should not be earthed at all.

It should be relatively easy to establish this by switching in and out strings of panels and hosing one of the strings (use care not to get electrocuted by the water stream!!). This is one of the reasons that I don't like these high voltage PV models, especially Voltronic ones that don't have insulation monitoring.