Online Impedance Estimation of Sealed Lead Acid & Lithium Nickel -
Cobalt - Manganese Oxide Batteries using a Rapid Excitation Signal
Abstract
Electrochemical Impedance Spectroscopy (EIS) has gained traction as a
technique apt for condition monitoring of batteries. The drawback of EIS
is that it is only applicable when the system is offline (i.e. it must
be disconnected from the load), takes a long time to complete and
requires an expensive equipment for measurement. This work aims to adapt
the EIS to serve as an in-situ measurement technique, that can be
utilized for online condition monitoring of two unique battery
chemistries – lead acid and lithium NCM. This work develops in twofold
– firstly, the Chirp broadband signal is proposed amongst a variety of
other broadband signals to significantly shorten the time required for
EIS measurement. Subsequently, a power converter that is typically used
to interface a battery with the load for current and voltage regulation
functions, is utilized for online condition monitoring of both batteries
through closed loop control of the power converter and duty-cycle
perturbation. This combined approach presents a novel low-cost technique
for online condition monitoring of batteries, with the ability to
complete battery characterization in a very short time. In this regard,
EIS measurement is completed for a lead acid battery (with lowest EIS
characterization frequency of 0.1Hz) in 5 seconds and lithium NCM
battery (with lowest EIS characterization frequency of 20mHz) in 25
seconds.