Development of an Intelligent Charger with a Battery Diagnosis Function Using Online Impedance Spectroscopy

Abstract

Battery diagnosis is vital to battery-based applications because it ensures system reliability by avoiding battery failure. This paper presents a novel intelligent battery charger with an online diagnosis function to circumvent interruptions in system operation. The charger operates in normal charging and diagnosing modes. The diagnosis function is performed with the impedance spectroscopy technique, which is achieved by injecting a sinusoidal voltage excitation signal to the battery terminals without the need for additional hardware. The impedance spectrum of the battery is calculated based on voltage excitation and current response with the aid of an embedded digital lock in amplifier in a digital signal processor. The measured impedance data are utilized in the application of the complex nonlinear least squares method to extract the battery parameters of the equivalent circuit. These parameters are then compared with the reference values to reach a diagnosis. A prototype of the proposed charger is applied to four valve-regulated lead-acid batteries to measure AC impedance. The results are discussed.

Electrochemical Impedance Spectroscopy as an Analytical Tool for the Prediction of the Dynamic Charge Acceptance of Lead-Acid Batteries

“…Interpreting EIS measurement is not straightforward, as the results found in the literature showed different shapes for battery, cell and half-cell spectra, mainly depending on the measurement regime, e.g., SoC, superimposed DC current and frequency range. For most EIS measurements, two capacitive semicircles can be identified [5,6,8,17,[35][36][37][38][39][40][41][42][43][44][45].…”

“…Interpreting EIS measurement is not straightforward, as the results found in the literature showed different shapes for battery, cell and half-cell spectra, mainly depending on the measurement regime, e.g., SoC, superimposed DC current and frequency range. For most EIS measurements, two capacitive semicircles can be identified [5,6,8,17,[35][36][37][38][39][40][41][42][43][44][45]. It is mostly agreed that each semicircle relates to one separate process of the electrochemical reaction, which could be charge transfer, chemical reactions, mass transport or adsorption processes.…”

Critical Review of Intelligent Battery Systems: Challenges, Implementation, and Potential for Electric Vehicles

“…It is desirable to use either low-cost or already deployed hardware for this purpose. This includes, for example, the use of active [296] and passive [143,147,297,298] cell balancers, as well as more advanced methods such as using charging circuits [299,300] or the EV's traction inverter [207]. Switched mode actuators can be further differentiated based on whether the energy used to excite the system is dissipated as heat [301][302][303] or redirected to reduce power dissipation [292,296,304].…”

“…A CSR is most commonly used for current sensing [207,268,296,303,311], but Hall-effect current transducers are utilized as well [112,293,294,301,302]. Low-cost implementations use MCU internal SAR ADCs [157,292,300,301,304] in most cases. For more performant systems, with an accuracy of >12 bit, standalone SAR or delta-sigma ADCs are employed typically [296,299,[311][312][313].…”

“…These approaches, however, are best suited for sinusoidal excitation and the absence of load current or other disturbances. More robust alternative approaches are based on correlation of current and voltage in a selected frequency range [268], the Goertzel algorithm [151,308,314], or single frequency DFT methods [296,300,311].…”