Is thermal runaway more likely in battery packs with multiple cells?

Cell-to-Cell Thermal Coupling

When multiple cells are connected in a battery pack, they can experience cell-to-cell thermal coupling, where heat generated by a single cell can transfer to adjacent cells. This can lead to a rapid increase in temperature, especially if the cells are densely packed or have limited thermal management. Studies have shown that even a small temperature increase of 1°C in a single cell can lead to a 2-3% increase in internal resistance, accelerating the thermal runaway process.

Mitigation Techniques

To mitigate the risk of thermal runaway in battery packs with multiple cells, designers and engineers can implement several techniques, including: (1) using thermal interfaces or pads to enhance heat transfer between cells, (2) employing thermal management systems such as heat sinks or air cooling, and (3) designing the pack with electrical isolation between cells to prevent the spread of thermal energy. For example, a study on lithium-ion battery packs found that using a thermal interface material with a thermal conductivity of 5-10 W/m-K can reduce the thermal resistance between cells by up to 50%.

Design Considerations

When designing battery packs with multiple cells, it’s essential to consider the thermal characteristics of the cells, the pack’s thermal management system, and the electrical connectivity between cells. For instance, using a battery management system (BMS) that monitors cell temperatures and can disconnect cells experiencing thermal runaway can help prevent pack-wide damage. Additionally, designers should consider the pack’s form factor and materials to ensure adequate airflow and thermal dissipation.