Batteries and Battery Management: Development of Low Cost, Rapid Impedance Measurement Equipment Suitable for Fast Analysis of Li-ion Cells

Batteries are a vital and integral part of modern life, installed in devices of every scale from personal portable electronic equipment to electricity grid energy storage. As people become increasingly dependent on battery energy sources, they also become increasingly reliant on accurate methods of quantifying the amount of useful energy available to them in order to function in their daily lives. Electrochemical Impedance Spectroscopy (EIS) is a branch of System Identification that can be used to identify battery metrics by which the remaining short-term (i.e. remaining charge) and long-term (battery lifetime remaining) life of a battery may be assessed. In this thesis the author gives an overview of battery chemistries and battery state estimation techniques before describing the development of a system capable of performing rapid impedance measurements. The development process spans two system designs, and results are given of impedance tests on lithium iron phosphate cells (LiFePO4) and lithium titanate (Li4Ti5O12) cells. A key feature of the method is to use Pseudo-Random Binary Sequences (PRBS) to approximate white noise, thereby providing equal stimulation of a wide band of frequencies simultaneously and reducing the required test-time. This document will be of use to those wishing to develop EIS test equipment at low-cost, and those who require a method of rapidly obtaining an impedance spectrum.