Meaning
Physical tendency of alternating current to distribute itself unevenly within a conductor, with the highest current density concentrated near the outer surface, increases the effective resistance at high frequencies. This skin depth effect alters the measured resistance of cell tabs, foils, and internal connections during high-frequency impedance testing.
Electromagnet Distortion
As the excitation frequency rises, the changing magnetic field induces eddy currents that oppose the primary current flow in the center of the conductor. Through the skin depth effect, the usable cross-sectional area of the conductor shrinks, which increases the effective ohmic resistance of the metal foils and terminal tabs. In high-power batteries, this phenomenon dictates the minimum thickness and material composition of current-carrying components to avoid excessive heat generation at high discharge rates or fast-charging profiles.
Frequency Limit
Depth of penetration varies inversely with the square root of the signal frequency and the conductivity of the material. For copper current collectors, this depth becomes a limiting factor in the megahertz range.
Sourcing Selection
Engineers designing high-power battery packs must account for this phenomenon when specifying busbars and terminal connections. Sourcing documents require suppliers to provide high-frequency electrical performance data to ensure the selected tab materials can handle the skin depth limitations.
