Maintenance measures for insulation performance of lithium battery packs

First, conduct regular insulation inspections

Detection tools and methods

Insulation resistance tester: This is the most commonly used tool for testing the insulation performance of lithium battery packs. Before use, make sure the tester is fully charged and calibrated accurately. When conducting the test, connect the high-voltage terminal of the tester to the positive or negative terminal of the battery pack (only measure the insulation condition of one terminal to ground at a time), ground the low-voltage terminal (the battery pack casing or reference ground), apply an appropriate test voltage (usually determined based on the rated voltage of the battery pack; for a 48V battery pack, a 500V test voltage can be selected), and read the insulation resistance value.

Megohmmeter: Its principle is similar to that of an insulation resistance tester. It detects insulation resistance by manually shaking the generator to generate high voltage. When operating, it is necessary to ensure a uniform shaking speed, generally maintained at around 120r/min, to guarantee the accuracy of the test results.

Detection cycle

For frequently used lithium battery packs, such as those of electric bicycles, it is recommended to conduct an insulation test once a month. This is because during daily use, battery packs may be affected by environmental factors such as vibration and moisture, leading to a decline in insulation performance.

Long-term storage scenario: If the lithium battery pack is in a long-term storage state, the insulation performance should be tested every 3 to 6 months. Changes in the storage environment, such as fluctuations in temperature and humidity, may gradually erode the insulating materials of the battery pack. Regular inspections can help identify potential problems in a timely manner.

Result determination and processing

The criterion for judgment: Generally speaking, the insulation resistance value of a lithium battery pack should be greater than a certain value to be considered qualified. For example, for low-voltage lithium battery packs (such as 12V - 48V), the insulation resistance value should be greater than 1MΩ; For high-voltage lithium battery packs (such as those of electric vehicles with a voltage of several hundred volts), the insulation resistance value should be greater than 100MΩ.

Abnormal handling: If the insulation resistance value is detected to be lower than the standard value, the battery pack should be immediately stopped from use and the insulation fault point should be further investigated. The method of segmented detection can be used to divide the battery pack into several parts and test the insulation resistance of each part separately, gradually narrowing down the fault range.

Second, maintain a dry environment

Storage environment control

Humidity requirement: Lithium battery packs should be stored in an environment with a relative humidity not exceeding 60%. Excessive humidity can cause moisture in the air to condense on the surface of the battery pack and even seep into its interior, reducing the insulation performance of the insulating material. For instance, during the rainy season in the south, the air humidity is relatively high. At this time, dehumidification equipment should be used to control the humidity of the storage environment.

Ventilation conditions: The storage area should maintain good ventilation to prevent the accumulation of moist air around the battery pack. Ventilation can also prevent the accumulation of trace gases caused by the weak self-discharge of the battery pack itself, reducing safety hazards.

Use environmental protection

Moisture-proof measures: When using lithium battery packs, if the environmental humidity is high, some moisture-proof measures can be taken. If a moisture-proof cover is installed outside the battery pack, it can prevent moisture from coming into direct contact with the battery pack. For some outdoor devices, such as the lithium battery packs of solar street lamps, drainage facilities can also be set up around the battery packs to prevent water from soaking them.

Avoid water splashes: During use, try to prevent the battery pack from being splashed with water. If water accidentally splashes onto the battery pack, it should be immediately wiped dry with a dry cloth and the insulation performance of the battery pack should be checked to see if it is affected.

Third, prevent mechanical damage

Installation and fixation

Proper installation: When installing lithium battery packs, ensure they are firmly installed to prevent displacement or damage due to vibration or collision during use. For instance, in electric vehicles, the battery pack should be fixed to the frame through dedicated brackets and bolts. The strength and rigidity of the brackets must meet the requirements to withstand various forces during the vehicle's operation.

Buffer protection: Buffer materials such as rubber pads and sponges can be added between the battery pack and the installation bracket to reduce the impact of vibration and shock on the battery pack. The cushioning material can also play a certain role in sound insulation, reducing the noise of the battery pack during operation.

Avoid external force collisions

Usage protection: Protective devices should be installed around equipment using lithium battery packs to prevent other objects from colliding with the battery packs. For instance, around the installation location of the battery pack of an electric forklift, metal guard plates can be installed to protect the battery pack from being hit by goods or other equipment.

Operating Procedures: When using the equipment, operators must strictly follow the operating procedures to avoid external force damage to the battery pack due to improper operation. When moving devices with lithium battery packs, handle them gently to avoid dropping them.

Fourth, maintenance of insulating materials

Regular inspection

Visual inspection: Regularly inspect the insulating materials on the exterior of the battery pack, such as insulating tape and insulating sleeves, to check for any damage, aging, or peeling. If any damage to the insulating material is found, it should be replaced in time. For instance, for some battery packs that are exposed outdoors for a long time, the insulating materials may age due to ultraviolet radiation, and it is necessary to enhance the appearance inspection.

Inspection of connection points: Focus on checking the insulation condition of the electrical connection points inside the battery pack, such as whether the insulation treatment between the battery terminals and the connection wires is intact. If the insulation at the connection points is damaged, it may lead to safety accidents such as short circuits.

Material replacement

Select appropriate materials: When replacing insulating materials, choose those that meet the design requirements of the original battery pack. The withstand voltage grade, insulation performance, temperature resistance performance and other aspects of insulating materials must all meet the usage requirements of the battery pack. For instance, for battery packs used in high-temperature environments, high-temperature resistant insulating materials should be selected.

Standardize the replacement operation: When replacing insulation materials, follow the standardized operation procedures to ensure the quality of insulation treatment. When winding insulating tape, pay attention to the number of layers and the tightness of the winding to avoid gaps or looseness.

Fifth, avoid chemical corrosion

Stay away from corrosive substances

Storage isolation: During the storage and use of lithium battery packs, they should be kept away from corrosive substances such as acids, alkalis and salts. These substances may corrode the casing and insulating materials of the battery pack, reducing its insulation performance. For instance, when storing lithium battery packs in the warehouse of a chemical enterprise, they should be placed in a dedicated anti-corrosion area and isolated from other chemical substances.

Usage protection: If the lithium battery pack must be used in an environment where it may come into contact with corrosive substances, protective measures should be taken. If an anti-corrosion coating is applied to the surface of the battery pack, or the battery pack is wrapped with anti-corrosion packaging materials.

Cleaning treatment

Timely cleaning: If corrosive substances accidentally splash onto the battery pack, immediately rinse with plenty of water and then dry with a clean cloth. For some stubborn corrosive substances, appropriate cleaning agents can be used for cleaning, but it should be noted that the cleaning agent must not cause damage to other components of the battery pack.

Check insulation: After cleaning up corrosive substances, carefully inspect whether the insulation performance of the battery pack has been affected. If necessary, conduct an insulation test.