To set the relay control mode, go to Battery → Relay Mode in the sidebar.

This setting determines how the BMS handles relay logic based on your system voltage and wiring.

1. Onboard HV Isolation Test

• Designed for high voltage systems
• Activates the full 3-relay setup including precharge and isolation test
• Matches the HV relay wiring described here

2. LV with Precharge

• For low voltage systems (e.g. 12 V or 24 V setups)
• Uses a simplified relay logic with optional precharge
• Matches the HV relay wiring described here

3. ReadBack Relays with STO
Only available on GRNbms_MK3_HV_STO

• Monitors relay state of battery plus and minus via 4 SPDT switches per relay
• Simple on/off switching without precharge
• Full monitoring of switch-on and switch-off process
• Includes a 24 V STO output to control external inverters
• Wiring diagram available here

⚠️ Make sure the selected mode matches your physical wiring, otherwise the system may not function correctly.

🔓 Each relay mode must be unlocked separately via grnbms.de.
Only the modes you've purchased will be available for selection.