In an off grid solar power system, the inverter and battery are both key components. The inverter's core function is to convert direct current (DC) to alternating current (AC), while the battery stores the energy generated by solar power generation. Common battery types include lead-acid and lithium batteries. Lithium batteries have become the mainstream energy storage option due to their high energy density and long cycle life.
In addition to power conversion, the inverter also performs other important functions, such as communication with the lithium battery's battery management system (BMS). This BMS communication between the inverter and the lithium battery plays a key role in the stable operation of the system.
A BMS (Battery Management System) can be considered the "brain" of the battery, responsible for monitoring and managing various operating parameters. Only lithium batteries are equipped with BMS communication. The inverter, on the other hand, serves as the energy coordination center of the entire system, converting the DC power from the photovoltaic panels and battery into AC power for use by the equipment. BMS communication bridges information exchange between the two. Through this communication mechanism, the inverter obtains real time battery status data, including key parameters such as charge level, voltage, current, and temperature. Users can dynamically adjust charging and discharging strategies based on this data, making precise energy management decisions. For example, when the battery charge approaches a critical level, the BMS sends a signal to the inverter, triggering protection mechanisms to prevent over discharge. This efficient collaborative operation not only optimizes the charging and discharging process but also provides users with more stable and reliable power support.
1. Real time Data Status Monitoring
Through BMS communication, the inverter continuously obtains dynamic battery operating information, providing users with more intuitive data support and facilitating subsequent analysis and optimization.
SOC (State of Charge) reading: This is one of the most critical parameters. The inverter obtains the precise remaining battery charge (percentage) from the BMS and displays it to the user. Without BMS communication, the inverter can only roughly estimate the SOC based on the voltage, which can result in significant errors.
State of Health (SOH) reading: Obtains battery health information and understands battery capacity degradation, which is used to evaluate battery life and system performance.
Voltage, current, and temperature reading: Obtains the battery pack's total voltage, total current, and temperature values at key temperature measurement points for real time monitoring and algorithm control.
Cycle count and capacity information: Obtains battery data such as total cycle count, rated capacity, and actual capacity.
2. Safety protection and alarm management
This is the most basic and important communication function. The BMS monitors all key battery parameters in real time. If anomaly is detected, it immediately notifies the inverter via communication, and the inverter then takes appropriate protective actions.
Overvoltage/undervoltage protection: If the BMS reports that the voltage of any battery cell or the total battery exceeds the safe range, the inverter immediately stops charging or discharging to prevent overcharging or overdischarging of the battery, thereby preventing fire or permanent damage.
Overcurrent protection: If the charge or discharge current is excessive, the BMS issues alarm, causing the inverter to limit current or disconnect the circuit to protect the battery and power devices.
High/Low Temperature Protection: When the BMS detects temperatures exceeding the safe operating range, it notifies the inverter to adjust power or shut down. Charging is prohibited when the temperature is too low to prevent lithium deposition; power is limited when the temperature is too high to prevent thermal runaway.
Short Circuit Protection: When the BMS detects a short circuit, it notifies the inverter to instantly disconnect the battery for short circuit protection.
Other faults, such as insulation faults, MOSFET faults, and balancing faults, are reported by the BMS, causing the inverter to generate an alarm and enter a safe state.
3. Charge and Discharge Control and Power Management
Based on the status information provided by the BMS, users can adjust the charge and discharge strategy in the inverter settings to optimize battery performance and lifespan.
Real Time Power Adjustment: Based on the battery's SOC, temperature, and health status, the BMS calculates and notifies the inverter of the "currently allowed maximum charge power" and "currently allowed maximum discharge power." For example, when the battery is low, high current charging is permitted; when the battery is nearly full, the BMS instructs the inverter to reduce the charging power until it switches to constant voltage trickle charging. At low temperatures, the BMS will significantly reduce the allowed charging current or even prohibit charging.
Charge and Discharge Start/Stop Control: The BMS can send commands to the inverter to start or stop the charging/discharging process. For example, when battery maintenance is required, the BMS can command the inverter to stop discharging.
The BMS communication connection between the inverter and the lithium battery runs through the entire energy storage system operation process. It is more than just a simple data transmission channel; it is a core mechanism for ensuring the safe and efficient operation of lithium battery. This mechanism maximizes battery safety levels and effectively extends battery life. Furthermore, combined with the inverter's charge and discharge strategies, it keeps the battery in optimal operating condition.
Xinton Power's full range of inverters supports lithium battery BMS communication. Hybrid inverters such as the Xindun HFP series, HF series, and HP PLUS+ series can seamlessly integrate and maintain stable communication with mainstream lithium battery on the market. Designed using standardized communication protocols, they support multiple communication methods, including CAN bus and RS485, ensuring real time exchange of critical operating data such as charge and discharge parameters, temperature data, and battery level information between the inverter and the battery management system. It allows users to grasp the working status of the battery system at any time, achieve more accurate charge and discharge control, effectively extend the service life of the lithium battery pack, and improve the safety and reliability of the entire energy storage system.
