Battery Thermal Management Methods

Intent: To educate readers on common PEV (Personal Electric Vehicle - EVs below size/carry capacity of a car) battery thermal management methods, and consequences of improper thermal management on rechargeable batteries.

Battery thermal management will always have a form of heat exchange system.

What is a heat exchanger? This is a glorified term for anything that can move heat from one place to another. For example, the copper pipes on your laptop/desktop CPU/GPU where it connects to heat sink/fin to a fan is a type of heat exchanger i.e. radiative, using a fan. Since this system requires power to operate, It can be considered as an active type of heat exchange.

Therefore, the definition of Active cooling in this scope of article (and generally, outside the article) means that the system transfers enthalpy from one place to another while using power. For example, a fan would be transferring electrical energy to ohmic heat (from coils of the fan) + Kinetic energy (to drive the fan itself), pulling/pushing air (containing heat, aka, enthalpy) from one place to another.

Passive cooling, in our scope, would be type of system that does not use energy to transfer enthalpy from one place to another: Heat sink/fins would be good example of this (and probably the only one, in the scope of this article). Since the system does not have a form of active device to block enthalpy transfer, this system, in theory, even out the temperature (enthalpy) of two system.

Practically speaking, most (if not all) e-bike batteries that are commercial uses passive cooling. Electric vehicles, however, often (if not always) employ some form of active cooling to manage enthalpy of batteries.