| PhD Viva

Name of the Speaker: Ananda S (EE16D004)
Guide: Dr. Lakshminarasamma N
Co-Guide: Dr. Radhakrishna V
Online meeting link: https://meet.google.com/snw-tyvn-hvj
Date/Time: 3rd April 2023 (Monday), 2.00 PM
Title: LITHIUM-ION CELL SORTING AND MODELING ELECTRICAL PERFORMANCE OF BATTERY FOR SPACECRAFT APPLICATION

Abstract

Lithium-ion batteries are the preferred energy storage devices in spacecrafts and other applications. The cells in these batteries could be arranged in series-parallel or parallel-series configurations. The cells must be sorted for the appropriate position within a series string or a parallel sub-module. The cell parameters are measured by testing, and then cell sorting is carried out. The conventional method of linear sorting is improved with the proposed Genetic Algorithm (GA) based sorting approach. This novel method (GA Improved Cell Sorting Algorithm - GICSA) ensures that more cells are available for battery making or closer matching between the parameters when both methods result in practically maximum feasible cell yield. Battery parametric estimation at a given point without the full capacity check option is needed in-field. It is made possible by the proposed Genetic Algorithm-driven Generic Estimation (GAGE) model. The spacecraft application is driven by limited charge power and charging time. Hence, energy balance estimation is needed with the electric load profile, charging profile, and battery parameters as inputs. An Energy Balance (EB) model is proposed to address the challenge. Both models carry out energy balance analysis over life with varying power generation and electric load profiles. For both models, 2% accuracy is achieved for battery voltage and deliverable capacity at different temperatures, State of Charge (SoC) ranges, on-ground tests and spacecraft operations in orbit.

The EB model is extended into the Cell Performance in Battery (CPB) model, which addresses self-discharge as a nonlinear function of SoC and temperature. The proposed CPB model enables the estimation of voltages of cells in spacecraft batteries with 2% accuracy under all operating conditions, including storage periods. A further improvement is proposed to get a Combined Model for the Cells in the battery and the equalization Electronics (CMCE). CMCE is validated for the charge equalization operation onboard a spacecraft.