Meaning
Thermal energy generated by the flow of electrical current through a metallic conductor constitutes a major source of heat in multi-cell assemblies. When current passes through these junctions, busbar resistance heating occurs as a function of the square of the current and the contact resistance of the connection. This thermal output can elevate the local temperature of the cells adjacent to the busbars.
Sourcing teams monitor this phenomenon to ensure that the joining method, such as laser welding or mechanical fastening, keeps the contact resistance within specified milliohm limits.
Material Selection
Conductivity and mechanical strength dictate the choice of metals used in high-current distribution systems. High copper or aluminum purity is common because these metals minimize the loss of energy as heat. If the selected grade of copper has impurities, busbar resistance heating increases and creates localized thermal hot spots.
This temperature rise can degrade the polymeric cell holders and accelerate the degradation of the battery chemistry.
Heat Mitigation
Design strategies to lower temperature rises focus on optimizing both surface area and connection pressure. Engineers often use nickel plating to prevent oxidation of copper surfaces, which would otherwise elevate the contact resistance. Applying a consistent clamping force or using specific welding patterns further reduces the thermal load.
These methods ensure that the assembly remains within safe operating limits under continuous high-rate discharge.
Safety Assessment
Elevated temperatures can trigger thermal runaway in adjacent cells if left unchecked. Testing protocols therefore measure the temperature rise at full continuous discharge to verify that the thermal management system can cope with the load.
