Online Impedance Estimation of Sealed Lead Acid & Lithium Nickel - Cobalt - Manganese Oxide Batteries using a Rapid Excitation Signal
preprintposted on 17.07.2020, 04:18 by Olakunle Alao, Paul Barendse
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.