Where does it come from?
Battery heat generation is not just about the ohmic I²R losses. There are three main contributors, each with distinct physical origins and implications for thermal modelling:
- Ohmic (I²R) – Heat from the electrical resistance in the electrodes, electrolyte, and current collectors. Dominant at high C-rates and low temperatures.
- Entropic – Reversible heat associated with entropy changes in the electrode reactions. This term can be positive or negative depending on the direction of current and state of charge.
- Hysteresis – Irreversible heat resulting from the voltage difference between charge and discharge OCV curves. Especially important in materials with large structural changes, such as LFP.
The magnitude and proportion of each component vary with temperature, C-rate, and state of charge. This makes accurate lab characterisation critical for building reliable thermal models and system-level simulations.
If you care about thermal performance or simulation accuracy, these terms must be included.
At About:Energy, we generate the high-fidelity data and validated models needed to capture these effects across the full operating range – supporting engineers in thermal design, pack development, and BMS strategy.
See also: Heat Generation in a Cell, Battery Thermal Management: Heat Generation, Cooling & TIM
Isn’t the hysteresis heat loss comes under the Ohmic losses or Joule heating? Both of them occur at the same time and are irreversible.