Part 7: Photovoltaic power station energy storage side battery management system (BMS) control level inspection and operation and maintenance SOP
This article corresponds to the panoramic topology diagram of the energy storage power station [Module 7: Battery Management System BMS], covering the three-level BMS (BMU ➔ BCU ➔ BAMS/BAU) hardware architecture, voltage/temperature sampling cable, CAN/RS485 bus terminal resistance test, active/passive equalization circuit maintenance, manual offline supplementary power depth equalization SOP, SOC/SOH algorithm calibration and protection parameter curing table.
1. Level 3 BMS hardware architecture, acquisition wiring harness and communication bus maintenance SOP
The three-level BMS architecture includes: BMU (single acquisition slave control layer), BCU (cluster-level control layer), and BAMS/BAU (array main control layer).
(1) Board inspection and wire harness sampling test
Node self-test and board inspection: Check the BMU, BCU and BAMS control board running indicators (the green Run light flashes, the red and yellow Error lights are off). Check that the addressing chip (ID Address) is configured correctly and there is no address overlap conflict.
Collection wire harness and NTC temperature probe plug buckle: Check the voltage sampling wire harness and temperature sampling cable on each Pack module to ensure that the connection buckle is locked firmly and is not loose due to vibration during power station operation.
Cell voltage sampling accuracy test: Use a Fluke 87V high-precision multimeter to measure the 10-cell cell pole voltage. Compared with the BMU monitoring screen, the voltage sampling error must be ≤ ± 2.0 mV.
Temperature sampling accuracy test: Use an infrared temperature gun to measure the surface temperature of the battery core, and compare it with the BMU temperature measurement NTC probe reading. The temperature sampling error must be ≤ ± 1.0 ℃.
(2) Communication bus (CAN/RS485) and terminal resistance test SOP
Terminal resistor impedance measurement: Disconnect the CAN bus control power supply and use the resistance range of a digital multimeter to measure the static impedance between CAN_H and CAN_L.
Standard: Since a 120 Ω termination resistor is connected in parallel at both ends of the CAN bus, the standard measurement impedance must be 60 ± 5 Ω. If the measured impedance is 120 Ω, it means that one end of the terminal resistor is off or disconnected; if the measured impedance is close to 0 Ω, it means that the CAN bus is short-circuited.
Communication packet loss rate monitoring: Capture messages through the BMS background. During 24-hour continuous operation, the CAN/RS485 bus communication data frame packet loss rate must be < 0.01%.
2. Active balancing and passive balancing circuit maintenance and offline power supply SOP
The balancing function is used to eliminate the capacity and voltage differences between cells and prevent the "barrel effect" from causing the capacity of the entire cluster to be discounted.
Passive balancing (discharge consumption type) circuit maintenance: Passive balancing converts the excess power of the high-voltage monomer into heat energy release through the power resistor on the BMU board (the balancing current is usually 50 ~ 150 mA).
Check: When equalization is started (such as cell voltage difference > 30 mV and cell voltage > 3.400 V), use an infrared thermal imager to scan the discharge resistor array on the BMU acquisition board. When passive equalization is turned on, the heating temperature of the resistor must be < 60.0°C, and there should be no burnt open circuit or thermal breakdown of adjacent sampling lines.
(2) Active balancing (energy transfer type) circuit maintenance: Active balancing uses a bidirectional DC/DC conversion module to transfer the energy of high-voltage cells to low-voltage cells (balanced current can reach 1 A ~ 5 A).
Efficiency test: Measure the DC/DC conversion efficiency of the active balancing module when transferring energy, which must be ≥ 85.0%.
(3) Manual offline power supply depth equalization SOP
When the extreme voltage difference of a certain cluster of cells is > 100 mV and BMS automatic equalization cannot eliminate it, manual offline power replenishment must be performed:
Step 1: Retrieve BMS monitoring data and lock the cell/Pack with the lowest voltage in the entire cluster (such as Pack 03).
Step 2: Shut down the system and cut off power, pull out the MSD manual maintenance switch of the cluster, and open the Pack 03 operation and maintenance cover.
Step 3: Connect the output end of the portable smart power supply meter to the positive and negative terminals of Pack 03.
Step 4: Set the charging parameters: limit the charging current to 20 A, and align the cut-off voltage with the highest cell voltage of the entire cluster (such as 3.400 V).
Step 5: Start power replenishment, and monitor the temperature rise of the internal unit of the Pack in real time during the process (must be < 40.0 ℃).
Step 6: Stop charging when the charging current drops to < 1 A, and read the voltage difference again after leaving it alone for 1 hour. The extreme voltage difference is < 15 mV, which is considered qualified.
3. Comparison of SOC/SOH core algorithm calibration and open circuit voltage (OCV) curves
(1) SOC (state of charge) algorithm calibration and OCV comparison table
BMS combines Coulomb Counting, Open Circuit Voltage (OCV), and Extended Kalman Filter (EKF) algorithms to calculate SOC in real time.
Lithium iron phosphate (LFP) battery cell 25 ℃ static open circuit voltage OCV and SOC comparison table:
Note: LFP batteries have an extremely flat voltage platform in the 30% ~ 80% SOC range, and must rely on the voltage endpoint to forcefully correct the SOC to 100% or 0% when fully charged (100% SOC) or empty (0% SOC).
(2) SOH (state of health) capacity degradation assessment and determination
Evaluation formula: SOH = (current fully charged available capacity Ah / rated nominal capacity Ah) × 100%.
Degradation disposal line: SOH ≥ 80%: normal operation stage; 70% ≤ SOH < 80%: the battery enters the accelerated degradation period, and the system is derated to 0.7C charge and discharge rate operation; SOH < 70%: reaches the retirement threshold, and applies for battery module echelon utilization or scrap replacement.
4. Full table of BMS system three-level protection parameter solidification and alarm response
Operation and maintenance personnel must check that the internal curing parameters of the BMS are completely consistent with the following table, and it is strictly prohibited to adjust the protection threshold without permission:
Photovoltaic power station energy storage side battery management system (BMS) control level on-site inspection sign-in form
Power station name: _______________________________ Inspection date: ____ month ____ day, 2026
Inspection area: BMS control board and sampling circuit in the battery compartment Inspection person in charge: ____________________
1. Field equipment inspection and test data records:
2. Inspection defect registration and defect elimination dispatch:
3. Inspection sign-in and review signature:
Inspection engineer (signature): _______________ Supervision engineer (signature): _______________
Review (signature) of the shift leader: _______________ Sign-in and filing time: ____ hour on ____ month ____ day 2026