New Storage Battery Impedance Evaluation Method Using Discharge Currents

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Abstract
The EU regulation presents several indicators to measure battery residual value, to reduce the environmental impact of battery manufacturing. IEC62620 has been identified as the standard to measure internal resistance, one of the defined indicators. While it describes a method for measuring AC internal resistance at 1 kHz, there are no reports of on-board measurement methods that can be directly incorporated into battery packs. This study proposes a new method for measuring the frequency dependence of the internal impedance of storage batteries and quantitatively validates for compliance with the International Electrotechnical Commission (IEC) standards and Japanese Industrial Standards (JIS). The proposed method utilizes the charging power of a storage battery to discharge it in the form of a square waveform. The frequency dependence of the impedance is determined through an active frequency sweep controlled by the Integrated Circuit (IC) developed in this work. High-precision measurements confirm that the proposed method complies with the IEC62620 standard for measuring the resistance component at 1000 Hz. Furthermore, it exhibits strong agreement with conventional methods within the estimated uncertainties in the 500 Hz – 2000 Hz frequency range. The proposed method is novel in that it employs square-wave discharge currents to evaluate the performance and reliability of storage batteries in accordance with IEC and corresponding JIS standards. This new method enables simpler and more compact systems that can be installed on-board, as opposed to conventional impedance measurements using sine waves. The proposed method has potential applications in reuse and recycling systems for storage batteries.

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