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Charge and discharge profiles of repurposed LiFePO4 batteries based on the UL 1974 standard - PubMed

  • ️Fri Jan 01 2021

Charge and discharge profiles of repurposed LiFePO4 batteries based on the UL 1974 standard

Hsien-Ching Chung. Sci Data. 2021.

Abstract

Owing to the popularization of electric vehicles worldwide and the development of renewable energy supply, Li-ion batteries are widely used from small-scale personal mobile products to large-scale energy storage systems. Recently, the number of retired power batteries has largely increased, causing environmental protection threats and waste of resources. Since most of the retired power batteries still possess about 80% of their initial capacity, their second use becomes a possible route to solve the emergent problem. Safety and performance are important when using these second-use repurposed batteries. Underwriters Laboratories (UL), a global safety certification company, published the standard for evaluating the safety and performance of repurposed batteries, i.e., UL 1974. In this work, the test procedures are designed according to UL 1974, and the charge and discharge profile datasets of the LiFePO4 repurposed batteries are provided. Researchers and engineers can use the characteristic curves to evaluate the quality of the repurposed batteries. Furthermore, the profile datasets can be applied in the model-based engineering of repurposed batteries, e.g., fitting the variables of an empirical model or validating the results of a theoretical model.

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Conflict of interest statement

The author declares no competing interests.

Figures

Fig. 1
Fig. 1

Standard charge and discharge processes of Li-ion battery. Step I (CC discharge): The battery is discharged at constant current Ic1 until the voltage drops to the cutoff voltage Vcut. Step II: Rest for the duration tr1 without the current pass. The voltage gradually rises to Vr1. Step III-1 (CC charge): The battery is charged at constant current Ic2 until the voltage rises to the threshold voltage Vth. Step III-2 (CV charge): The battery is charged by maintaining Vth until the current reaches the cutoff current Icut. Step IV: Rest for the duration tr2 without the current pass. The voltage gradually drops to Vr2.

Fig. 2
Fig. 2

Two-tier DC load method for measuring the DCIR of batteries. The DC load test measures the battery’s internal resistance by reading the voltage drop. In the two-tier process, the DCIR is obtained by the Ohm’s law, dividing the voltage variation (V1−V2) by the current variation (I2−I1). The DC load test is the preferred method for evaluating the battery characteristic of DC power consumption.

Fig. 3
Fig. 3

Battery test system. The CTE-MCP-5082020A battery test system (made by Chen Tech Electric Mfg. Co., Ltd., Taiwan) is used for evaluating the performance of the battery cells. There are 16 channels, and each of them can provide measurements of voltage, current, and temperature simultaneously.

Fig. 4
Fig. 4

(a) Marking rule for the repurposed battery cell and the file folder in the database. (b) Naming rule for the charge and discharge profiles according to test procedures 1 and 2.

Fig. 5
Fig. 5

Central tendency of the DCIRs R85 and R20. The distributions of R85 and R20 exhibit the central tendency. (a) For R85, most values locate around the central value 0.0095 Ω (red arrow). (b) For R20, most values locate around the central value 0.0165 Ω (blue arrow).

Fig. 6
Fig. 6

Four-probe method and temperature measurement. A current is passed through the outer probes (contacts 1 and 4) and induces a voltage in the inner voltage probes (contacts 2 and 3). The current and voltage can be measured simultaneously with high accuracy during the charge and discharge processes. On the other hand, the thermocouple locates at the center of the cylindrical surface of the cell for temperature measurement (red dot 5).

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