Air cooling of Li-ion batteries. An experimental analysis

Electric vehicle industry has been rapidly developing internationally due to the renewed interest in low- or zero-emission vehicles. So far, Lithium-Ion batteries, is the technology that best fits the needs of electric vehicles, due to their large specific energy density and specific power, making these cells ideally suited for high rate-of-discharge applications such as during acceleration. In spite of this, there are safety concerns using Lithium-ion cells because of the use of high energy materials. Heat is a major battery killer and Lithium secondary cells need careful temperature control. Operating at high temperatures brings on a set of different problems which may result in the destruction of the cell: unless heat is removed faster than it is generated, a thermal runaway may occur. Tests with an air cooling system were carried out using an experimental loop specially designed: the tests were performed on a module consisting of four pouch cells, manufactured by EiG, connected in series. The module was discharged with a current of 80 A (4C discharge) and cooled with air at velocity ranging from 0 to 7 m/s. It was found that it is possible to completely discharge the batteries using air velocities higher than (or equal to) 4 m/s. Increasing the air velocity the temperature difference between the centre of the cell and the electrodes decreases. In spite of this, it was not possible to reach a uniform temperature distribution within a cell, and within the pack, using air as cooling fluid