Meaning
Electrical contact resistance at welded tab terminals converts high current throughput into localized Joule heating within cell interconnections. Measuring tab heating contact resistance isolates voltage drops across mechanical and welded joints from internal cell electrochemical impedance. The metric applies to cell-to-busbar and tab-to-terminal connections under active current flow, ending when current drops to zero.
Pack design engineers measure tab heating contact resistance to evaluate weld joint quality and prevent localized thermal degradation at terminal connections. Interfacial oxide layers, surface contamination, and insufficient weld area increase localized junction resistance.
Interface Resistance
Microscopic surface asperities restrict actual electrical contact area to small localized points across welded tab interfaces. High tab heating contact resistance generates excessive localized heat during fast charging, raising terminal temperatures well above internal cell core values. Excessive junction heat degrades surrounding plastic busbar insulation and risks melting structural module frame components.
Thermal conduction from hot tabs into the cell core creates steep internal temperature gradients that accelerate localized electrode aging. Ultrasonic wedge bonding and laser welding parameters dictate effective interface contact area and joint microstructural integrity. Intermetallic compound formation within dissimilar metal welds increases joint electrical resistance and lowers mechanical shear strength over time.
Continuous vibration during vehicle operation degrades micro-welds, gradually elevating contact resistance and localized heating rates during service life.
Localized Heating
High current flow through elevated joint resistance creates hot spots that damage tab seal integrity, risking electrolyte leakage. Minimizing tab heating contact resistance requires optimizing laser welding laser power profiles and maintaining strict surface cleanliness standards. Automated four-wire Kelvin sensing systems measure terminal micro-ohm voltage drops during pack assembly lines to catch defective welds.
Joint Quality
Quality assurance protocols reject busbar weld joints that exceed defined micro-ohm resistance thresholds during inline production checks. Lowering tab heating contact resistance prevents thermal runaway initiation originating at high current busbar connection points. Technical procurement contracts specify maximum allowable contact resistance values for supplied battery module assemblies.
Accelerated environmental testing exposes tab joints to thermal cycling and corrosive salt spray to verify long term electrical interface stability. Precise joint manufacturing ensures stable power delivery and prevents localized thermal damage across high power battery systems.
