Passive thermal management

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Enclosure

The sealed case that carries the modules, protects them in a crash, keeps water out to an IP67 rating or better and vents gas in a thermal event. In many cars it is a structural part of the body.

Heat sink

A metal body, often extruded aluminium with fins, that draws heat from a component and enlarges the surface it can lose that heat from. Fins multiply the area for convection to air; in batteries heat sinks serve air-cooled cell blocks and, above all, the balancing resistors and power switches of the BMS and DC/DC converter.

Phase change material

A material that melts at a chosen temperature, around 30–45 °C for batteries, absorbing a large latent heat — roughly 200 J/g for paraffin wax — with little temperature rise. Packed around cells, often in a graphite matrix to lift its poor conductivity, it caps peaks during short heavy loads, but it must be cooled to reset and adds mass.

Thermal management

Keeping cells in their comfortable range, roughly 15–35 °C, and within a few degrees of each other: liquid cooling plates, refrigerant plates or immersion for heat removal, and heaters or waste heat for warming before fast charging in the cold.

Thermal mass

A body’s total heat capacity seen as a buffer against temperature change. A 500 kg pack at about 1 kJ/(kg·K) stores roughly 500 kJ per kelvin, so 10 kW of uncooled heat warms it only about 1.2 K a minute. Together with the thermal resistance to the coolant it sets the pack’s thermal time constant.

References & further reading

Technical references

1. University Physics Volume 2, §1.6: Mechanisms of Heat Transfer

   OpenStax, Rice University

   Technical reference · Conduction, convection, radiation and thermal resistance.

Further reading on this topic

These sources provide broader context; they are not presented as citations for every statement in this entry.

2. A General Energy Balance for Battery Systems

   Dawn Bernardi, Ellen Pawlikowski, John Newman · Journal of The Electrochemical Society · 1985

   Topic background · Battery energy balance and irreversible and reversible heat contributions. Reduced thermal models require explicit assumptions and current-sign conventions.