I have a 8kw Deye inverter with 2 Volta stage 1 batteries. The problem is that only the Master battery discharges and nothing from the Slave battery. If the charge om the slave go below 50% it starts to draw currant from the grid. If I switch the Master battery of the slave battery start to supply power to the inverter. That started during a 4 day power outage the we had the past week. What can be the cause and what must be done to rectify this situation. Thanks Willem