This wiring example shows how to connect a GRNbms MK3 system in a low-voltage setup, using three relays and a precharge resistor.
It is intended for 12 V or 24 V systems and uses the „Jump Start“ 12 V input for powering the BMS.

LV Relay Wiring Diagram

• HV Battery: Supplies the low-voltage system (e.g. 12 V / 24 V)
• Fuse: Protects the entire system from overcurrent
• HV Relay Precharge: Routes current through the precharge resistor to limit inrush
• HV Relay Positive: Connects main power after precharge
• HV Relay Negative: Closes the negative path to the load
• Precharge Resistor: Limits inrush current to the inverter during startup
• Current Shunt: Measures current flowing to the inverter
• Inverter: The main load (can be any DC consumer)
• Jump Start Input: Powers the BMS directly with 12 V via GND / 12 V input pins

• Connect 12 V to the Jump Start input on the BMS
• The BMS uses this input to power itself – no high voltage required

The BMS controls all three relays directly via its outputs:

• Precharge relay closes briefly to limit inrush
• Positive and Negative relays close after precharge completes
• The BMS monitors all timing and status automatically

• Termination resistor and CAN wiring must still be set correctly
• Precharge path must include the shunt to allow current monitoring during startup
• This wiring is intended for LV systems only – use HV wiring for 150–1200 V setups

🔥 Always follow safety guidelines and consult a professional installer.
Incorrect wiring can cause damage, malfunction, or fire. Use at your own risk.