David Xu
Power / Controls
Li-ion battery is widely used in the application where energy storage is required. Most of the batteries are tested in the factories to guarantee the quality of the cell. Such testing system usually consists of a programmable power supply, a environmental controlled chamber and an automation system to connect the batteries for testing. The computer (central controller) commands the robots to connect the cells, power supply to charge or discharge the cells and the chamber to maintain the temperature. When the batteries are in the end market for several years, such testing becomes necessary for users to know the performance of the battery cells. The portable cell testing system for users is necessary. In this project, a small portable Li-ion battery cell testing system is built to test the single battery cell to find out the battery performance.
The objective is to build a single cell battery testing system with micro-controller. The tester is for Li-ion 18650 battery with a maximum of 3AH battery. The system should have a container for battery under test, a programmable power supply to charge/discharge the battery, a micro-controller with display and necessary sensors.
To the performance the test, the system should have following accuracy:
1) Voltage measurement: <=5mV (or 0.1%)
2) Current measurement: <=5mA (or 0.1%)
3) Temperature: 0.5 Celsius
The programmable supply should be able to perform a maximum of 2C(6A) charging/discharging with control accuracy of 1%.
The display should be able to display following information:
1) Battery voltage
2) Charging/discharging current.
3) Battery temperature
4) State of charge (SOC)
The team is suggest to find suitable ICs to perform the Li-ion battery monitoring as well as the charging/discharging controller. Also some IC manufactures provide the SOC calculation in the chip. The students should be able to understand from the application notes and other sources.
1) How to use the power IC and how to improve the accuracy of sensors.
2) How to communicate the IC with micro-controller to perform the test.
3) How to calculate the SOC using either specific IC or micro-controller. Simple SOC algorithm with Coulomb counting is suggested.
The group is responsible for providing the management and demonstration of the project based on the course outline.
Student A is suggested to have the knowledge of power electronics. The project requires to build the programmable charging/discharging power supply. Student A is responsible for the power supply design, hardware assembly and debugging.
Student B is suggested to have the knowledge of sensors including voltage/current sensor as well as the temperature sensor. Student B is required to design the sensor circuit (independent of the power circuit), assemble and debug the circuit.
Student C is suggested to be familiar with micro-controller. The knowledge includes MCU programming, communication with ICs (power and sensor) and LCD display. The SOC may be calculated in the MCU. The student is responsible for the implementation of SOC algorithm.
DX01: Li-ion battery cell testing system | David Xu | Wednesday September 19th 2018 at 08:55 AM