Analysis of Voltage and Current Signal Processing in a Li-ion Battery Management System

The Naval Postgraduate School’s Battery Management System (BMS) manages Li-ion batteries in a possible storage system for pulsed power weapons aboard Naval Vessels. The system charges the batteries with a buck converter according to the Constant Current Constant Voltage method. The BMS uses analog equipment to measure signals and then digitally converts signals for transmittal to a Field Programmable Gate Array (FPGA). Software processing controls the voltage and current directed to the batteries to maintain proper control and maintenance of the batteries. Based on the BMS’s successful operation, the processing of voltage and current signals in the BMS is researched and documented in this thesis. The documentation is provided through a thorough signal analysis before and after each component. Specifically, the current signal is analyzed and the processes of a Hall Effect Sensor, an instrument amplifier, and an analog-to-digital converter are described. Additionally, the voltage signal and its processing by a voltage-to-frequency converter are analyzed and the FPGA programming is described. The accuracy of the collected data is shown and possible improvements to the system are documented.