Abstract:
This Thesis deals with impedance measurement of Li-ion Batteries using White
noise like Pseudo Random Binary Sequence (PRBS), Battery Parameters like State of
Charge, State of Health and Remaining useful life can be calculated using battery
impedance, but it is quite difficult to extract on-board, it is possible to extract impedance
of battery using Excitation signal like PRBS, using this PRBS method simulations and
experiments are performed with different set of batteries and using different set of PRBS
signals, A different set of approach is used in this experiment this technique uses
Randles’ equivalent battery model in Simscape MATLAB, Battery parameters including
series resistance, charge transfer resistance and double layer capacitance are found
through Electrochemical Impedance spectroscopy. Input current is fed as square
charging and discharging pulses. Battery has dynamic behavior in which all parameters
in a battery tends to change with temperature and its operating conditions, that change in
parameters predict a battery’s life and other characteristics.
Hardware is also built to perform the experiment using different sets of battery with
predefined impedance to verify our results in simulations using excitation signal. It is
calculated that using excitation signal like PRBS can generate a electrochemical
impedance spectrum in limited frequency range like any high quality laboratory
impedance analyzer. This method of calculating Impedance is suitable for many
applications with different temperature and charge. Impedance calculations are
performed in low frequency signal to obtain best results, usage of high frequency PRBS
signals is found to be difficult to obtain impedance in this experiment. Hardware
combination comprises of PCB, a FPGA, and a battery cell. Hardware is capable of
estimating battery impedance using Pseudo Random Bit Sequence PRBS signals and
monitor State of charge of a battery without disconnecting it form its circuit. PRBS
signal is fed to battery and monitor its voltage curve which on further processing gives
its internal impedance. This impedance plays a crucial role in estimating battery state of
health and its remaining useful life.
