Investigation of Air Flow Cooling of Li-Ion Batteries

Lithium -ion batteries are used in electric cars, hybrid cars and Boeing 787 Dreamliner. There is an issue with heat generation in these batteries that may cause fire and reduce performance. An experimental chamber has been setup that provides dynamic and static cooling/heating regimes for Li-ion batteries. Air flow is produced by air station with maximum output of 80 m3/h. The maximum possible pressure drop is 7000 Pa. Air station can work both in pumping and exhausting mode. This test setup will be used to study various surface topology to enhance heat transfer without increase weight. Experimental setup contains two-stage temperature stabilization system. During the first stage we use the preliminary heating or cooling of the inlet air in the air buffer. The aim is to achieve the air temperature close to required inlet temperature. During the next stage air passes through the chamber with temperature controller where eventually the flow temperature is set. This approach provides flow temperature stabilization within −30°C to +50°C range with 0.2°C accuracy. For our studies we have designed and manufactured simulators of Li-ion battery power cells with the same thermal properties as the original ones. Each simulator contains 40 surface temperature sensors (20 per side). The data from sensors is transferred to computer by the NI-6225 PC card for control and further processing. The design of the simulators provides information about the placement of cooling surfaces with various surface elements and its efficiency — fins, triangles, wings, etc. In this paper, the characteristics of cooling surfaces with filleted pins will be reported. We have measured the surface temperature distributions and obtained the corresponding cooling diagrams for 10–40°C temperature range and 1 m/sec – 4 m/sec flow rates. The experimental results are compared to the computer simulation using SolidWorks Flow Simulation™ software.