Meaning
Dynamic heat generation disparity between charge and discharge directions arises from reversible entropic changes combined with irreversible resistive dissipation within an electrochemical cell. In battery thermal management design, thermal dissipation hysteresis describes why a cell releases heat at different rates when operated at identical current magnitudes under reversed power flow. The metric dictates heat rejection requirements across duty cycles.
It applies during active current flow, stopping when the cell reaches thermal equilibrium under zero current rest.
Entropic Vector
Reversible heat generation depends on the temperature coefficient of open circuit voltage. During charging, entropy changes within active material crystal structures can endothermically absorb heat or exothermically release it depending on state of charge. When current direction reverses during discharge, this entropic term reverses sign, producing asymmetric total heat profiles despite identical ohmic loss contributions.
Cooling Specification
Thermal management system sizing must accommodate peak heat generation rates occurring during the exothermic cycle phase. Liquid cooling systems designed for average thermal output risk local overheating during high discharge events. Control logic adjusts coolant flow rates dynamically based on current direction and state of charge to prevent thermal gradients across large module packs.
System integration engineers account for heat release asymmetries when designing thermal barrier layers between adjacent cells.
Thermal Limit
At high C-rates, irreversible ohmic heating overwhelms reversible entropic heat components. The directional heat generation gap narrows as resistive dissipation dominates total thermal output.
