I am in the process of designing a Victron based ESS system. I have an old existing PV system that will remain in place, to be AC coupled on the load side.
The panels are still performing very well and will most likely last another decade or even two. The inverter (after a couple of warranty replacements in the early years) has now worked for 11 years. It is likely to be worn out some time in the near future.
When that happens I want to keep the PV panels. The problem is that they are SunPower panels from the early days, and need the positive side grounded to avoid significant degradation of output from a build up of charge on the surface (up to 30% reduction). With PV inverters grounding is only safe if the inverter is galvanically isolated, essentially transformer based. And those kind of inverters no longer get produced.
In comes the SmartSolar MPPT RS: it would be the perfect replacement to directly charge the batteries in the new ESS from the old panels. Not only is it isolated, removing any risk the positive grounded panels could pose downstream, the MPPT RS 450-100 has the perfect DC voltage range and current capacity for the existing array. Direct drop-in replacement without a need to re-wire anything on the roof.
But then I find this in the manual:
“3.2. MPPT grounding, detection of PV array insulation faults & Earth fault alarm
notification
The RS will test for sufficient resistive isolation between PV+ and GND, and PV- and GND.
In the event of a resistance below the threshold (indicating an earth fault), the inverter shuts down and disables the ac outputs (mppt keeps charging the battery as this has no impact on safety due the isolation to the battery side).”
I hope that paragraph is just a copy & paste error that made it into the MPPT RS manual from a different product. To the best of my understanding the MPPT RS has no inverter, only MPPT. So it should work without any issues, correct? Or if it actually had ground fault detection, would there be any way to turn that off in the configuration?
Assuming the MPPT RS gets the tick of being fine with a positive grounded array: what are Victron’s product cycles like, is there any advance warning before a product gets discontinued? I would hate to design the ESS system around the idea of adding the MPPT RS later and then no longer be able to actually purchase it.
I’ll want the ESS to be installed early next year, but the inverter replaced by the MPPT RS only when the old inverter fails, in 1, 2, 3,… years.
All this is in the interest of minimizing waste. I don’t want to throw out a good inverter now, nor do I want to throw out perfectly good panels in a few years…