116 Chapter 10 For example, as the cells are discharged they generate heat, that heat will be transferred via conduction to the bus bars and any other components that are in direct contact with the cells. Convective heating and cooling is most typically seen through the use of a liquid cooling plate; however, the movement of cooled air can also provide convective cooling. This is where most of the cooling will take place in the battery system. Finally, radiant heating must be considered in a couple of important areas. First, the radiated heat from the cell to other components that are not in direct contact with the cells can impact adjacent cells.
Second, the heat that is being generated from components such as the electronics will impact the cells if it is not properly managed. Sources of heat generation inside a battery system come from the chemical reaction within the cell (the main area of heat generation) as the lithium-ions move back and forth during operation; balancing of cells (usually while parked); electronics within the battery pack; and thermal management system. While the lithium-ion cells are the primary source of heat generation inside a pack, the influence of the electronics must not be disregarded as it can be a significant source of heat creation that must be accounted for in your thermal management system design.
If adequate shielding and consideration of the placement of these electronics are not considered, then the heat generated by the electronics may actually have a negative impact on the cells life. Figure 1 below offers some simple examples of each of these three methods of heat transfer. In this example, a pouch-type lithium-ion cell is shown with a cooling plate on the right and Bus bar Conduc on Radia on Conduc on & Convec on Adjacent frame Cooling plate Lithium-ion cell Figure 1 Sources of heat in a lithium-ion battery.