===== Low Voltage Relay Wiring – with Precharge =====

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.

''⚠️ **Voltage Range:** The BMS accepts only **10 V to 17 V** at the Jump Start input.\\
If your battery voltage is outside this range (e.g. 24 V system), you **must use a DC-DC converter** to step the voltage down to a safe level.''

''💡 Using too high a voltage on the 12 V input can **damage the BMS**!''

''🔥 Always follow safety guidelines and consult a professional installer.\\
Incorrect wiring can cause **damage, malfunction, or fire**. Use at your own risk.''{{:mk3:screenshot2025-04-07200216.png?nolink&793x418}}

==== Components Overview ====

  * **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
==== BMS Power Supply (LV Mode) ====

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

==== Relay Control ====

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

👉 We recommend using relays with economizer to avoid unnecessary load on the BMS power supply