Does the CellMate-K9/WatchMonCORE have the ability to shut off the current to/from the battery directly? Or does it need to rely on relays, etc to start/stop the current flow?
It relies on communication with the inverter and circuit breaker for critical disconnect. The ability to use relay control for charge/discharge exists, but a mechanical device does not make sense for high power.
For large currents, solid-state relays are generally not adopted due to power loss, with the preferred method being to control the inverter.