Design of Calorimeter and Heat Measurement of Lithium-ion Battery

Abstract

Since the temperature of the lithium-ion battery has a great impact on its performance and life, heat generation measurement of the lithium-ion battery becomes one of the most important parts of designing lithium-ion battery and battery manage system (BMS). Commercial calorimeters are widely used in measuring heat generation rate of the lithium-ion battery but fail to measure large heat generation rate, and the response is slow. Therefore, this thesis presents a new calorimeter that consists of two thermal electric modules (TEMs) and two metal plates can measure large heat generation (120W) with a quick response (100s). A test station that constitutes with a bipolar power supply, an electronic load, and a DC power supply is built to test the designed calorimeter and the lithium-ion battery, it can charge/discharge the battery with any current profiles. All the equipment in the test station is controlled by LabVIEW. In order to identify the parameters of the metal plate and calibrate the calorimeter, a printed circuit board (PCB) is used as a dummy heat source. The PCB has the same size as the battery and is assumed to have a pure electrical resistance. Therefore, the heat generation of the lithium-ion battery can be simulated. In order to control the temperature of the lithium-ion battery, different control methods are designed to control the current that is applied to the TEM. A lead-lag compensator has been selected by comparison because of its response time and stability. The calorimeter is thermally modeled based on the equation of energy balance of the metal plate. MATLAB/Simulink is used to simulate the calorimeter and the results are compared with the experimental data to validate the accuracy of the model. Based on the thermal model of the calorimeter, Kalman filter is used to estimate the heat generation rate of the lithium-ion battery. Finally, Kalman filter is implemented using MATLAB and integrated into LabVIEW to measure heat generation rate of the lithium-ion battery in real-time. The designed calorimeter is able to measure the heat generation of the lithium-ion battery accurately and fast.