Optimization of the discharge cut-off voltage in LiFePO4 battery packs

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Considering that the voltage and capacity/energy level of a single battery cell cannot meet the requirements of electric vehicles, hundreds of battery cells are usually connected in series/parallel. The discharge cut-off voltage of the battery cells is an important factor affecting the consistency of the terminal voltage and the capacity usage efficiency (i.e., the ratio of the discharged capacity to the nominal capacity) for a battery pack. This paper presents an optimization method for determining the LiFePO4 battery cell discharge cut-off voltage considering three factors: capacity usage efficiency, terminal voltage dispersion, and minimum terminal voltage. By applying this optimization method to different number of series-connected battery cells, the relationship between the optimized discharge cut-off voltage and the number of battery cells is deduced, and this relationship is instructive for the operation of the battery pack. Compared with the conventional method where the discharge cut-off voltage is 2 V, the terminal voltage dispersion is greatly reduced and the maximum rate of variation is 10.7%. At the same time, the minimum terminal voltage increases by about 1.5% and the capacity usage efficiency only declines by about 0.5%. Consequently, the battery cells will not be over-discharged because the minimum terminal voltage is larger than 2 V. The rate of decline of the capacity usage efficiency is small and it can be ignored. Moreover, the level of consistency among the terminal voltage of the battery cells is improved and lifetime of the battery pack will be extended.
OriginalsprogEngelsk
TitelProceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 )
Antal sider8
ForlagIEEE Press
Publikationsdatosep. 2019
StatusUdgivet - sep. 2019
Begivenhed2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe) - Genova, Italien
Varighed: 3 sep. 20195 sep. 2019

Konference

Konference2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe)
LandItalien
ByGenova
Periode03/09/201905/09/2019

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Electric potential
Electric vehicles
Electron energy levels

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Sui, X., He, S., Jinhao, M., Stroe, D-I., Huang, X., & Teodorescu, R. (2019). Optimization of the discharge cut-off voltage in LiFePO4 battery packs. I Proceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 ) IEEE Press.
Sui, Xin ; He, Shan ; Jinhao, Meng ; Stroe, Daniel-Ioan ; Huang, Xinrong ; Teodorescu, Remus. / Optimization of the discharge cut-off voltage in LiFePO4 battery packs. Proceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 ). IEEE Press, 2019.
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title = "Optimization of the discharge cut-off voltage in LiFePO4 battery packs",
abstract = "Considering that the voltage and capacity/energy level of a single battery cell cannot meet the requirements of electric vehicles, hundreds of battery cells are usually connected in series/parallel. The discharge cut-off voltage of the battery cells is an important factor affecting the consistency of the terminal voltage and the capacity usage efficiency (i.e., the ratio of the discharged capacity to the nominal capacity) for a battery pack. This paper presents an optimization method for determining the LiFePO4 battery cell discharge cut-off voltage considering three factors: capacity usage efficiency, terminal voltage dispersion, and minimum terminal voltage. By applying this optimization method to different number of series-connected battery cells, the relationship between the optimized discharge cut-off voltage and the number of battery cells is deduced, and this relationship is instructive for the operation of the battery pack. Compared with the conventional method where the discharge cut-off voltage is 2 V, the terminal voltage dispersion is greatly reduced and the maximum rate of variation is 10.7{\%}. At the same time, the minimum terminal voltage increases by about 1.5{\%} and the capacity usage efficiency only declines by about 0.5{\%}. Consequently, the battery cells will not be over-discharged because the minimum terminal voltage is larger than 2 V. The rate of decline of the capacity usage efficiency is small and it can be ignored. Moreover, the level of consistency among the terminal voltage of the battery cells is improved and lifetime of the battery pack will be extended.",
keywords = "Batteries, Battery Management Systems (BMS), Hybrid Electric Vehicle (HEV, Efficiency, Optimal control",
author = "Xin Sui and Shan He and Meng Jinhao and Daniel-Ioan Stroe and Xinrong Huang and Remus Teodorescu",
year = "2019",
month = "9",
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booktitle = "Proceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 )",
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Sui, X, He, S, Jinhao, M, Stroe, D-I, Huang, X & Teodorescu, R 2019, Optimization of the discharge cut-off voltage in LiFePO4 battery packs. i Proceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 ). IEEE Press, 2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe), Genova, Italien, 03/09/2019.

Optimization of the discharge cut-off voltage in LiFePO4 battery packs. / Sui, Xin; He, Shan; Jinhao, Meng; Stroe, Daniel-Ioan; Huang, Xinrong; Teodorescu, Remus.

Proceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 ). IEEE Press, 2019.

Publikation: Bidrag til bog/antologi/rapport/konference proceedingKonferenceartikel i proceedingForskningpeer review

TY - GEN

T1 - Optimization of the discharge cut-off voltage in LiFePO4 battery packs

AU - Sui, Xin

AU - He, Shan

AU - Jinhao, Meng

AU - Stroe, Daniel-Ioan

AU - Huang, Xinrong

AU - Teodorescu, Remus

PY - 2019/9

Y1 - 2019/9

N2 - Considering that the voltage and capacity/energy level of a single battery cell cannot meet the requirements of electric vehicles, hundreds of battery cells are usually connected in series/parallel. The discharge cut-off voltage of the battery cells is an important factor affecting the consistency of the terminal voltage and the capacity usage efficiency (i.e., the ratio of the discharged capacity to the nominal capacity) for a battery pack. This paper presents an optimization method for determining the LiFePO4 battery cell discharge cut-off voltage considering three factors: capacity usage efficiency, terminal voltage dispersion, and minimum terminal voltage. By applying this optimization method to different number of series-connected battery cells, the relationship between the optimized discharge cut-off voltage and the number of battery cells is deduced, and this relationship is instructive for the operation of the battery pack. Compared with the conventional method where the discharge cut-off voltage is 2 V, the terminal voltage dispersion is greatly reduced and the maximum rate of variation is 10.7%. At the same time, the minimum terminal voltage increases by about 1.5% and the capacity usage efficiency only declines by about 0.5%. Consequently, the battery cells will not be over-discharged because the minimum terminal voltage is larger than 2 V. The rate of decline of the capacity usage efficiency is small and it can be ignored. Moreover, the level of consistency among the terminal voltage of the battery cells is improved and lifetime of the battery pack will be extended.

AB - Considering that the voltage and capacity/energy level of a single battery cell cannot meet the requirements of electric vehicles, hundreds of battery cells are usually connected in series/parallel. The discharge cut-off voltage of the battery cells is an important factor affecting the consistency of the terminal voltage and the capacity usage efficiency (i.e., the ratio of the discharged capacity to the nominal capacity) for a battery pack. This paper presents an optimization method for determining the LiFePO4 battery cell discharge cut-off voltage considering three factors: capacity usage efficiency, terminal voltage dispersion, and minimum terminal voltage. By applying this optimization method to different number of series-connected battery cells, the relationship between the optimized discharge cut-off voltage and the number of battery cells is deduced, and this relationship is instructive for the operation of the battery pack. Compared with the conventional method where the discharge cut-off voltage is 2 V, the terminal voltage dispersion is greatly reduced and the maximum rate of variation is 10.7%. At the same time, the minimum terminal voltage increases by about 1.5% and the capacity usage efficiency only declines by about 0.5%. Consequently, the battery cells will not be over-discharged because the minimum terminal voltage is larger than 2 V. The rate of decline of the capacity usage efficiency is small and it can be ignored. Moreover, the level of consistency among the terminal voltage of the battery cells is improved and lifetime of the battery pack will be extended.

KW - Batteries

KW - Battery Management Systems (BMS)

KW - Hybrid Electric Vehicle (HEV

KW - Efficiency

KW - Optimal control

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M3 - Article in proceeding

BT - Proceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 )

PB - IEEE Press

ER -

Sui X, He S, Jinhao M, Stroe D-I, Huang X, Teodorescu R. Optimization of the discharge cut-off voltage in LiFePO4 battery packs. I Proceedings of 21st European Conference on Power Electronics and Applications (EPE' 19 ). IEEE Press. 2019