Daily maintenance and inspection of lithium battery packs are core tasks for ensuring system safety, extending service life and preventing faults. They should be carried out around five dimensions: electrical performance, mechanical condition, thermal management, environmental adaptability and software monitoring. The following is the specific list of inspection items and the analysis of key points:

First, electrical performance inspection

Voltage consistency detection

The voltage difference of a single cell should be ≤50mV (for new battery packs) or ≤100mV (for aged battery packs), and the total voltage fluctuation should be ≤5% of the rated value.

Method: Use a high-precision multimeter or a battery management system (BMS) monitoring module to record the voltage data at the end of charging and discharging.

Abnormal handling: If the voltage difference continues to expand, it is necessary to check for self-discharge of the battery cells, loose connection terminals or sampling errors in the BMS.

Internal resistance and capacity testing

The increase in the internal resistance of the battery cell should be no more than 20% (compared with the factory value), and the remaining capacity should be no less than 80% of the rated value (within the nominal number of cycles).

Method: The internal resistance is measured by an AC internal resistance meter (at a frequency of 1kHz) or the pulse discharge method. Complete the capacity calibration in combination with the charge and discharge tester.

Abnormal handling: An abnormally high internal resistance may be accompanied by aging of the battery cells or local overheating. Further testing of the consistency of the battery cells is required.

Insulation resistance monitoring

The insulation resistance between the positive and negative poles and the housing should be ≥500MΩ (for high-voltage systems, it should be ≥1GΩ).

Method: Use an insulation resistance tester (500V/1000V range) for the test, and record the influence of environmental humidity on the results.

Abnormal handling: A decrease in insulation resistance may be due to seal failure, wire harness damage or dust intrusion. Special attention should be paid to inspecting high-voltage connectors and sealing rings.

Second, mechanical condition inspection

The tightness of the connection terminals

The torque value of the bolts should comply with the design specifications (for example, the torque of M6 bolts is 8-10N·m), and there should be no signs of loosening or oxidation.

Method: Use a torque wrench for random inspection to observe whether there are green corrosion substances or black oxide layers on the surface of the terminals.

Abnormal handling: Loose terminals will cause an increase in contact resistance, leading to local overheating. They need to be re-tightened and conductive paste applied.

Shell integrity

There should be no deformation, cracks or seepage, and the sealing rubber strips should not fall off or age.

Method: Visually inspect the surface of the casing and gently tap it to listen for any hollow sounds (possibly due to loose internal fasteners).

Abnormal handling: Damaged casing may cause water ingress or short circuit. The machine must be stopped immediately and the casing replaced.

Stability of the fixed bracket

The bracket should be free from looseness, breakage or deformation, and the battery pack should be closely attached to the installation surface.

Method: Check the tightness of the bracket bolts and use a feeler gauge to measure the gap between the battery pack and the installation surface (≤0.5mm).

Abnormal handling: Loose brackets can cause intensified vibration, accelerate the damage of battery cells, and require re-fixation and the addition of anti-loosening gaskets.

Third, thermal management inspection

Temperature uniformity

The temperature difference between battery cells should be ≤5℃ (static) or ≤8℃ (dynamic), and the maximum temperature should be ≤55℃ (charging) or ≤60℃ (discharging).

Method: Monitor the temperature distribution through BMS or infrared thermal imager, and record the temperature rise curve during the charging and discharging process.

Abnormal handling: Local overheating may be due to poor heat dissipation or uneven internal resistance of the battery cells. It is necessary to clean the heat dissipation channels or replace the abnormal battery cells.

Efficiency of the heat dissipation system

The flow rate of the liquid cooling system should be no less than 90% of the design value, and the wind speed of the air cooling system should be no less than 2m/s.

Method: Use a flowmeter to detect the flow rate of the liquid cooling system and an anemometer to measure the wind speed at the air inlet of the air cooling system.

Abnormal handling: Insufficient flow may be due to pipeline blockage or pump failure. It is necessary to clean the pipeline or replace the pump.

Thermal runaway protection

The explosion-proof valve is not clogged, the pressure relief channel is unobstructed, and the pressure of the fire extinguishing device (such as aerosol) is normal.

Method: Visually inspect the surface of the explosion-proof valve and use a pressure gauge to measure the pressure of the fire extinguishing device.

Abnormal handling: Blockage of the explosion-proof valve can lead to the inability to release pressure in time when thermal runaway occurs. The sealing parts need to be cleaned and replaced immediately.

Fourth, environmental adaptability inspection

Cleanliness

Requirement: No metal debris, conductive dust or corrosive liquid residue.

Method: Use a vacuum cleaner to clean the surface dust, and use a cotton swab dipped in alcohol to wipe the connector contacts.

Abnormal handling: Metal debris may cause short circuits. Thorough cleaning and inspection of environmental protection measures are required.

Humidity and Corrosion

Requirements: Environmental humidity ≤75%RH (no condensation), no rust on metal parts.

Method: Use a hygrometer to monitor the environmental humidity and visually inspect the surface of metal parts.

Abnormal handling: In high-humidity environments, dehumidification equipment should be added. Rusted parts need to be derusted and coated with anti-rust paint.

Waterproof and dustproof grade

Requirements: Comply with the design IP rating (such as IP67), and the sealing ring should not be aged or damaged.

Method: Visually inspect the condition of the sealing ring. If necessary, retest the IP rating (such as a spray test).

Abnormal handling: If the seal fails, replace the sealing ring and reassemble it. Ensure that the installation surface is flat and free of scratches.

Fifth, software monitoring and data recording

BMS log analysis

Requirements: No frequent alarm records (such as overvoltage, undervoltage, over-temperature), SOC estimation error ≤5%.

Method: Export the BMS log, analyze the alarm type and occurrence time, and verify the SOC accuracy using a charge and discharge tester.

Abnormal handling: Frequent alarms may be due to sensor failure or improper parameter Settings. The sensor needs to be calibrated or the protection threshold adjusted.

Traceability of historical data

It is required to keep charging and discharging records, temperature curves and alarm logs for at least six months.

Method: Regularly back up BMS data to the cloud or local server to generate trend analysis reports.

Exception handling: Data loss may be due to storage device failure. Redundant storage needs to be added and data integrity should be checked regularly.

Firmware and parameter update

The BMS firmware version should be the latest, and the protection parameters (such as overcharge/overdischarge thresholds) should comply with the design specifications.

Method: Check the firmware version through a dedicated tool and verify the protection threshold by comparing it with the parameter table.

Exception handling: If the firmware version is too old, there may be security vulnerabilities. It is necessary to upgrade it in a timely manner and test new functions.

Sixth, key points for maintaining typical application scenarios

Electric vehicle

Key points: The impact of fast charging on battery life, and loose connections caused by vibration.

Measures: Check the number of fast charging cycles and the internal resistance of the battery cells every month, and tighten the high-voltage connectors every quarter.

Case: A certain electric vehicle failed to check the internal resistance after fast charging, which led to an accelerated decline in the capacity of the battery cells and a 30% increase in later maintenance costs.

Energy storage system

Key points: Electrolyte decomposition caused by long-term float charging and control of environmental humidity.

Measures: Conduct balanced charging every six months and install industrial dehumidifiers to control humidity.

Case: Due to the failure to control humidity in a certain energy storage power station, the BMS circuit board was corroded, and the system downtime was extended to 72 hours.

drone

Key points: Cell displacement caused by vibration and performance degradation in low-temperature environments.

Measures: Check the fixed status of the battery pack after each flight and preheat the battery in a low-temperature environment.

Case: Due to the failure to preheat the battery of a certain drone, the voltage dropped sharply during low-temperature discharge, increasing the crash rate by 20%.