This was originally a reply to another post.
Relay DCH is meant to be connected to all Victron loads and charge devices. (Non Victron loads can be added here in a single contactor configuration) The BMS will first issue pullback commands to the Victron inverters, MPPTs and chargers on the VE.CAN network. If the system continues to over or under charge, it will open the DCH relay based on the BMS cell high and low settings.
The second relay (CH)is meant to be used with old style devices that can not be shut down via CANBus or an opto coupler interlock circuit and the REL1 and REH1 settings are used for that. See attached sketch.
This configuration allows for a 3 stage shutdown process and an example might be something like this:
- BMS detects an approaching UV cell condition
- First it issues a CANBus command to shut down the Victron inverter to reduce the system load
- cell voltage continues to drop.....
- Second, it issues a CH Relay1 open command based on the voltage levels set using REL1 and REH1, which will shut down all manually connected loads
- cell voltage continues to drop .....
- Third, as a final safety it issues a DCH relay open command and all Victron devices are disconnected
If you set RE1H to a positive value it is used for UV (under voltage) applications where you want to shut down a manual load
If you set RE1H to a negative value it is used for OV (over voltage) where you want to manually disconnect charging devices.
If you set both to 0V it is disabled
Clarification from Tine at REC.
ABMS for Victron already has the Discharge/MAIN relay programmed for UV and OV protection and wiring the CHARGE relay is not required. CHARGE relay may be used for OV and UV for other purposes and is configurable with instructions RE1L and RE1H. If the RE1H is positive it is for UV protection, negative for OV protection, if set to 0 V it is disabled. The customer may connect any signal to the CHARGE F input. Some of the devices are controlled by applying ground so ground is connected to fused input and NO then connected to a controlling device.
