Hallo, How can I share solar panels, Pylontech batteries, and MPPT for two independent Multiplus 2 systems, each with ESS?
Two separate dwellings, each with its own electricity meter from the distribution company.
Thank you
you cannot share with 2 ESS.
If all the equipment is located at one installation point, then it would be possible to run 2 independent systems off one battery, one could run ESS, the other probably not. CAN data from the battery can be shared to 2 Cerbos, Then the MPPT controllers can be connected to either.
If the equipment is not located at one point, then this becomes more difficult as the battery would have to be split, and a dc bus used to connect both haves of the battery.
If you do want to run 2 ESS systems, then you would also need to split the PV charging.
Just as a thought experiment: an ESS needs two data sources, a BMS and a grid meter. The BMS can even be very stupid, a two-wire BMS.
So, one system is a full ESS, as you would configure it standalone, that is in charge of managing the BMS/DVCC, and the MPPT. Depending on the grid regulations, this might also export to the grid.
The second is running its own Cerbo, knows nothing about the MPPT, and has the BMS configured as two-wire, where the “discharge enabled” signal is tracking the real signal from the battery, while the “charge enabled” is hardwired to “off”. It’s configured to neither export nor import, just keep the grid meter at 0, and supply loads when the grid fails.
Then you might write one of those dbus python scripts to check the second system’s AC power and reduce grid export in the first system, to avoid exporting when the excess PV power might be needed in the second system.
A more realistic way would probably be, regulations permitting, to give up the grid connection in one dwelling and hook this up to the first via a smartmeter, and run just one standard ESS installation for both of them; and then use the meter readings to split the cost in whatever way is appropriate.
Hi Christian, The second system doesn’t need to run in 2 wire mode - the 2nd Cerbo can share the same CAN data from the BMS as the ESS system. It may or may not have an mppt connected to it, but it will still shut down the inverter if battery condition warrants. If the MPPT is connected to it, then it will also control that suitably.
The second system should not operate as an ESS - as this would cause double the export / import to the battery, thus offsetting the ESS operating point. If export is allowed, then one connection should be sufficient to export the excess.