Transient Thermal Analysis on Cell Stack Design for Lithium-Ion Battery Backup Unit in Data Center

Lithium ion battery solution has attracted much research interest owing to its high energy storage density, outstanding discharging performance, and long service life. Battery backup unit (BBU) is designed to take over immediately power delivery when power outage or power surge occurs, providing enough time for data center to back up data. Transient analysis of the heat transfer process once the battery discharging starts is important since the data backup duration is short, typically in several minutes and the discharge current can be higher than 10C. It is crucial to make sure that the battery cells in backup units are not overheated during this process. In this study, transient thermal analysis was performed for a battery backup unit during discharging which was cooled by forced air flow. A lumped thermal model for a single cell was implemented after determining the heat generation during cell discharging and the equivalent homogenous thermo-physical properties within the cell. Battery skin temperature was measured during discharging and the experiment data were compared to validate the lumped thermal model. Thermal performance of the air-cooled BBU with different cell stacking designs are simulated and discussed.