There are many battery cooling options, which is better or best depends on the cell selection and application. There is no right and wrong. However, let’s look at them and at a first attempt list of advantages and disadvantages.
Note: all of the images show a section through cylindrical cells, but each of these cooling methods are application to all cell formats.
Passive Cooling
The cell or cells are held in an enclosure, this enclosure could have dual functions (eg mobile phone). Heat generated by the cell is conducted, convection or radiated to the enclosure and vice versa.
Typically used for low power applications and where the ambient conditions are below 35°C.
Examples: mobile phone, electric drill, Nissan Leaf
Passive Cooling + Fan
The cell or cells are held in an enclosure, a fan is used to move air around the enclosure and hence help to create a more even temperature profile across all cells.
Heat generated by the cell is conducted, convection or radiated to the enclosure and vice versa.
Typically used for low power applications and where the ambient conditions are below 35°C.
Examples: Renault Zoe (?)
Forced Air Cooling
The cell or cells are held in an enclosure, air is forced through the battery pack and cools the cells. This approach can use waste cabin air that will have been filtered and cooled.
Examples: Toyota Prius
Have you designed an alternative cooling system that you would like to share and explain how it works on batterydesign.net? Drop me a line: nigel@batterydesign.net
Cooling Plates
An encapsulated cooling fluid that is circulated to the battery where heat is transfered to and from the fluid. Heat is removed and added to this fluid away from the battery pack using a radiator and/or heat exchanger.
Probably the most common battery cooling system used in electrified vehicles as the system can use water-glycol as the cooling fluid.
Examples: Porsche Taycan
Dielectric Immersion Cooling
The cells are immersed in a dielectric and the dielectric then flows through a heat exchanger to extract the heat. The dielectric is in direct contact with the cells and busbars and hence thermal barriers are minimised.
Examples: Koenigsegg Regera, Mercedes C63 AMG
Phase Change Material
A solid to liquid phase change material is packaged next to the cells. This temperature at which the material changes phase is normally set around 50 to 70°C so that it can essentially add thermal inertia to overheating cells.
Examples: ? (don’t know of any examples in production – please comment below)
Phase Change Cooling Plates
The cells are thermally connected to a refrigerant cooling plate. This is seen as less complex in the automotive industry as it removes the intermediate water-glycol system and applies the refrigerant system directly to the cells. Thus removing a number of parts, making it possibly cheaper and lighter.
Examples: BMW i3, Mercedes S400 Hybrid
We are sure this is not all of the cooling system options and we would really like to know what we missed, leave a comment below or email us at nigel@batterydesign.net
Heat Generation in a Cell
Heat generation in a cell can be defined quite simple for the case where the cell is operating within it’s normal limits. The first expression gives the heat flow [W].
The first part of this equation is the irreversible Joule heating term, the I2R term.
The second part is the reversible entropy term or Reaction heat terms. The charge and discharge reaction can be exothermic or endothermic under certain conditions.
Thanks for sharing. I think passive cooling via heat pipe and then dumping that heat to the heat sink is also explored thermal management strategy.
Hi Vinayak, this would need a heat sink outside and so probably falls into the liquid cooling option, but using a means to move the heat from the cell to the liquid. Were you thinking that? Best regards, Nigel
Very interesting overview. What would you say are the drawbacks for immersion cooling technology?
Hi Julius, an interesting question as there are quite a few pros and cons, however, I will pull this out as a separate page on each technology. Best regards, Nigel
Hello Nigel,
Great summary.
Do you know if the Battery cooling plates and Di-electric immersion cooling retain their structural rigidity and No leak condition (Coolant + Electric charge) in Vehicle Crashworthiness.
Hello Kartik, I think this is a problem. With cooling plates the connections and plates themselves are likely to get split and hence leak into the pack. Some designs such as the Porsche Taycan place the cooling system under the pack enclosure with an impact and insulation tray below that.
Dielectric cooled systems are also likely to get damaged and leak dielectric. This can be a significant issue if the dielectric is being used to control cell thermal runaway.
Hope that helps, best regards, Nigel
Thank you my good sir.
Nice overview. Couple of quick questions:
(1) How does these cooling schemes vary based on battery type (i.e. cylindrical, prismatic, or pouch) – which type lends itself to better/efficient heat management?
(2) What are your thoughts on flow (or redox flow) battery tech?
1. Cooling options versus cell formats would be an interesting post. I will have a think about that.
2. Flow batteries are great for large stationary energy storage systems, cooling should be possible with a heat exchanger.
Nigel, look into EGO batteries as an example of phase change material cooling.
https://egopowerplus.com/innovation
Calvin, can you share any data that shows cell temperature over a power cycle with and without the phase change material?