You need to implement two control layers:
- The BMS controls the inverter through data communication, prefered a CAN-Bus. Here the information about allowed charge and discharge currents needs to be communicated to the Deye hybrid inverter. This can also include to stop charge and discharge by communicating according charge or discharge currents as 0A, when battery is full or empty.
- A relay can only be the last option, if data communication and current limitation fails.
These relays can not switch high currents a lot of times. That can do that in emergency and should only do that in emergency situations.
And I am sure you will damage not only the relay but also the inverter if you cut charge or discharge currents a lot.
To sum this up: I would suggest to only use a single kilovac to cut the battery in emergency situations. And yes, I am also using a precharge unit. And how to control that is described here.
Some more explanations:
I use Victron Energy inverters. Discharging is stopped by the BMS through sending “discharge current limit” as 0A. Charging is stopped by having
a) a maximum charge voltage of 3.45V per cell (LFP) defined in the inverter
b) Batrium sends a dynamic charge voltage between 3.37V and 3.45V to the inverter (Dynamic Voltage Targets).
If battery is full and inverter tries to charge more, it can not due to configured maximum charge voltage. If battery is empty and inverter does not act on Batriums command, CriticalOK state will become false and single central kilovac will open.