MSXIV: Four methods for cooling the pack was discussed: Liquid Cooling, In this page, air cooling (specifically, active air cooling) and liquid cooling will be discussed as a cooling method for the battery module of MSXV vehicle. Phase Change Interstitial Material , Forced Air Cooling, and Conductive Cooling to catamaran. Of those four options, Forced Air Cooling was chosen; Liquid Cooling and Phase Change Interstitial Material were thought to be more superior in terms of performance than Forced Cooling, but they were either way too complicated and risky to produce or were not mentioned as they are either unable to be acquired . Conductive Cooling to Catamaran would simply be or ineffective due to the terrible thermal conductivity. Battery Pack Cooling
Air Cooling
A significant advantage of Air Cooling is that it is way more simple and crude than Liquid Cooling, which was the reason why it was chosen for MSXIV. It is also cheaper to produce as the only device we need is a set of fans.
According to this page Specific Heat Capacity of the Battery Pack, it is calculated that the system with the use of the Noctua NF-F12 iPPC 3000 fan could would be able to provide “enough cooling power to keep the pack at a maximum of 45 degrees given our worst case conservative estimates.” However, the problem faced here is that “the cooling and temperature distribution within the pack is NOT uniform” as estimates” if we consider our battery pack as a single module.
However, there was a structural problem with this cooling method. As you can see from the diagram below, the cooling and temperature distribution within the pack was not uniform.
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The This page Battery Pack Temperature Distribution - adjusting cell spacing tells us that cause of the problem here is that the not much air is flowing through the middle of the pack, causing the interior cells to heat up 10-15 degrees more than the exterior cells. The possible solution proposed by Micah is to “move the cells further apart in the middle in order to get more airflow through the module, essentially creating an airflow channel within the pack.” The MSXII took similar approach, as “fans [were] mounted inside the box and air will flow along the length of the box.”
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Battery Pack Temperature Distribution - adjusting cell spacing
Testing - Cooling Methods and Temperature Distribution under High Loads
TESLA: On the other hand, Tesla has chosen Liquid Cooling by developing a system called BMS (Battery Management SystemHowever, this heat distribution problem seems to be a fundamental issue of air cooling. According to this article https://insideevs.com/news/482245/nissan-leaf-repair-liquid-cooling-benefits/, Nissan Leaf - the world’s first mass-market electric vehicle - also has the same problem. This particular Nissan Leaf has driven 120,000 miles (which is A LOT), and its rare stack module was extended, thus causing range issues. The mechanic explains that happened because the rear module stack is the one that gets the hottest due to the limitations of Air Cooling system.
Liquid Cooling
Liquid Cooling more efficiently distributes heat over more convection surface area than pure conduction. In other words, Liquid Cooling is just more efficient, and this is why many of the newly launched electric vehicles are equipped with Liquid Cooling. https://www.intel.com/content/www/us/en/gaming/resources/cpu-cooler-liquid-cooling-vs-air-cooling.html#:~:text=According%20to%20Mark%20Gallina%2C%20liquid,more%20efficient%2C%20and%20often%20quieter.
The other advantage of Liquid Cooling is that it will not have heat distribution issue as vehicles with air cooling system did. That’s because cooling tube in which coolant flows through contacts with each and every individual cell. The diagram below is Tesla’s Battery Management System (BMS). The way the BMS cools individual batteries is to make a ribbon like pipe snake through the battery pack so that it contacts with each and every cell, as you can see below.
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This way, we can have higher energy density than using a straight pipe because multiple cells can be packed closely together.
In order to prevent the tube breaking and leaking the coolants, Tesla has chosen to use metallic inner tube, and Glycol flows through the tube as the coolant.
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And here's full Model S battery module.
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Information for this paragraph was taken from here:
https://www.easyelectriccars.com/why-do-tesla-batteries-not-overheat-teslas-battery-cooling-system/
P.S. this design is patented.
Conclusion
Air Cooling and Liquid Cooling each has pros and cons. Air Cooling is simpler and cheaper, whereas Liquid Cooling is more efficient and does not have heat distribution issue. So far, it seems that it is worthwhile to attempt to build Liquid Cooling system if time permits as it is superior in terms of performance and does not have structural issue.
Useful Resources