Key points for maintenance of connection parts of lithium battery packs

The connection parts of lithium battery packs (such as tabs, busbars, wire terminals, etc.) are the core channels for current transmission, and their reliability directly affects the performance and safety of the battery pack. If the connection parts become loose, oxidized or overheated, it may cause an increase in resistance, local heating or even the risk of thermal runaway. The following analysis is conducted from three aspects: daily inspection, maintenance operation and preventive measures.

First, key points of daily inspection

Appearance integrity inspection

Check if the connection parts are deformed: Observe whether there are any signs of bending, breaking or melting on the tabs, busbars or wire terminals. For example, if local discoloration or melting pits are found on the busbar, it may be due to excessive contact resistance causing overheating.

Check if the insulation layer is damaged: Inspect whether the insulation layer of the wire is cracked or worn to avoid the risk of short circuit. Especially in a vibrating environment (such as in electric vehicles), special attention should be paid to the friction areas between the wires and the metal brackets.

Signs of corrosion: Check for white powder (alumina) or green rust spots (copper corrosion) at the connection points, especially in damp or salt spray environments, where more inspection is required.

Confirmation of fastening status

Bolt/nut tightening torque: Regularly use a torque wrench to check whether the tightening torque of the connecting bolts meets the design value (for example, the battery pack of an electric vehicle usually requires 8-12 N·m). If the torque is insufficient, it may lead to an increase in contact resistance.

Elastic gasket condition: If spring washers or locking washers are used at the connection parts, it is necessary to confirm whether they still have elasticity to avoid loosening due to vibration.

Temperature monitoring

Infrared temperature measurement: Use an infrared thermal imager to regularly scan the connection parts, with a focus on abnormal temperature points (such as those more than 5℃ higher than adjacent areas). For instance, in a certain energy storage power station, due to poor welding between the busbar and the electrode tabs of the battery cells, the local temperature reached 80℃ (normally it should be below 50℃).

Historical data comparison: Establish a temperature reference value. If the temperature at a certain connection part continues to rise, the cause should be investigated in a timely manner.

Second, maintain operation norms

Cleaning treatment

Remove the oxide layer: If oxidation occurs at the connection point, gently sand it with sandpaper (such as 400 mesh) or a copper wire brush until it reaches a metallic luster. Avoid using acidic cleaners (which may accelerate corrosion).

Anti-corrosion coating: After grinding, apply conductive grease (such as anti-oxidation paste containing zinc powder) to reduce the corrosion of metals by environmental humidity.

Insulation layer repair: If the insulation layer of the wire is damaged, it should be re-wrapped with heat shrink tubing or insulating tape to ensure that the coverage extends at least 20mm beyond the damaged area.

Fastener maintenance

Staged tightening: For multi-bolt connections (such as parallel busbars of battery modules), they should be tightened 2 to 3 times in a diagonal sequence to prevent deformation caused by force on one side.

Anti-loosening measures: In a vibrating environment, thread locking adhesive (such as medium-strength detachable type) or self-locking nuts can be selected, but it is necessary to avoid the adhesive from seeping into the conductive contact surface.

Inspection of the welding area

False soldering detection: Test the firmness of the soldering by slightly shaking the wire. If any looseness is found, re-soldering is required. For instance, the battery pack of a certain unmanned aerial vehicle suddenly lost power during flight due to a false weld between the tabs and the wires.

Solder joint morphology: Normal solder joints should be smooth and conical. If cracks or burrs occur, they need to be cleaned and re-welded.

Third, preventive maintenance strategies

Environmental control

Humidity management: Keep the humidity of the battery pack storage environment below 60% to prevent oxidation of metal components. For instance, during the rainy season in the south, it is necessary to add dehumidification equipment or use moisture-proof bags.

Dust prevention measures: In dusty environments (such as mining equipment), it is necessary to regularly clean the accumulated dust at the connection points to prevent insulation degradation or poor heat dissipation caused by dust.

Vibration suppression

Application of shock-absorbing pads: Rubber shock-absorbing pads can be installed at the connection points of battery packs near vibration sources (such as beside motors) to reduce the transmission of vibration.

Wire fixation: Use wire clips or cable ties to secure the wires to the bracket to prevent fatigue and breakage at the connection points due to shaking.

Regular maintenance plan

High-frequency usage scenarios: such as electric vehicles or energy storage power stations. It is recommended to conduct a comprehensive inspection every 3 to 6 months. Low-frequency usage scenarios (such as backup power supplies) can be extended for up to one year.

Maintenance record: Establish a maintenance file for connection parts, recording the inspection time, operation content and replaced parts to facilitate problem traceability.

Fourth, Common Problems and Emergency Response

Overheating of the connection part

Reasons: Increased contact resistance (such as oxidation, loosening), overload or poor heat dissipation.

Handling: Immediately stop the machine and cut off the power. After the connection parts have cooled down, check the fastening condition and oxidation. Replace the damaged parts if necessary.

Wire breakage

Reason: Long-term bending fatigue or external force pulling.

Treatment: Cut off the broken part, re-press the terminal and wrap it with an insulating layer; If the fracture location is close to the battery TAB, the entire wire needs to be replaced.

Insulation failure

Reason: Insulation layer damage or excessive environmental humidity.

Treatment: After repairing the insulation layer, use an insulation resistance tester (such as the 500V range) to measure the resistance to ground and ensure that the value is greater than 1MΩ.