SMM News: Panasonic has developed a new battery management technology to measure the electrochemical impedance of batteries and effectively evaluate the residual value of stacked lithium-ion batteries, which is expected to be used in vehicles in the future. Panasonic partnered with Professor Masahiro Fukui of Li Mingguan University to develop the technology. Panasonic developed a new battery monitoring IC (BMIC) test chip, measurement algorithm and software to evaluate the actual effectiveness of LMU batteries.
The new battery management technology uses AC excitation method to measure the electrochemical impedance of stacked lithium ion battery modules. In addition, the residual value is evaluated by deterioration diagnosis and fault evaluation according to the measured data. This will help to promote the recovery and reuse of lithium-ion batteries and achieve sustainable development.
This new technology has the following characteristics:
1 。 The electrochemical impedance of multi-cell battery pack was measured by BMIC technique.
Conventional BMIC can measure the voltage of lithium-ion batteries stacked from 6 to 14 cells. In a battery management system, voltage data can be obtained from more series battery cores (up to 200) through multiple BMIC, to monitor battery operation status and ensure safe use. In addition, the charging and health status can be evaluated, and the remaining mileage and time can be calculated.
In addition to the traditional functions, the newly developed BMIC test chip also has a built-in electrochemical impedance measurement function, which is measured by AC excitation method. Electrochemical impedance measurement is realized by 15 fully parallel analog / digital converters, pulse modulated AC excitation circuits from 0.1Hz to 5khz, and complex voltage / complex current conversion circuits built into BMIC. Therefore, the BMIC chip can measure the electrochemical impedance of the battery while running without the need for major adjustments to the current BMS configuration in the battery.
2 。 In the electrochemical impedance measurement, the measurement accuracy is the same as that of the standard instrument.
The Cole-Cole diagram drawn by complex impedance was measured and the state was evaluated by electrochemical impedance spectroscopy (EIS). Li Mingguan University used BMIC and measurement software developed by Panasonic to measure cylindrical lithium-ion batteries. The results show that the Cole-Cole diagram can be measured and drawn in the frequency range from 1Hz to 5KHz, and the accuracy is the same as that of industrial standard measuring instruments.
3 。 Through the temperature calibration technology, we can respond to the temperature change of the operating equipment.
The electrochemical impedance of lithium ion battery is very sensitive to temperature change. Therefore, when using special measuring instruments in the laboratory, the battery should be placed in a constant greenhouse to maintain a constant temperature. For the battery module in the process of operation, it is impossible to measure the electrochemical impedance of the battery module because of the continuous change of ambient temperature. Therefore, Japan Rimingkuan University and Panasonic have developed a temperature correction technology, in the process of electrochemical impedance measurement, measure the temperature of lithium ion battery, correct the impedance temperature change to the standard temperature, and draw it on the Cole-Cole diagram. In this way, even if the ambient temperature changes with the seasons and time alternating, it can be corrected to the standard temperature in the database according to the Cole-Cole diagram.
The new technology is suitable for equipment and vehicles with multi-cell lithium-ion batteries, such as electric bicycles, low-speed vehicles, construction and logistics machinery, and can be used in electric vehicles and high-capacity batteries in the future.
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