Normally there are four type work model of ESS
Work Mode 1
Energy produced by the PV system is preferred for local load. And the excess energy is first used for charging batteries, then feeding to the grid.
Work Mode 2
If there is no PV, battery energy is used for local load first, the grid also can supply when the battery capacity is not enough.
Work Mode 3
If the grid is fault or there is no grid, the system can still work, PV and batteries supply energy for local load.
Work Mode 4
The battery can be charged by the grid, time and power of battery charging can be set up flexibly.