Modeling of Lithium Battery Cells for Plug-In Hybrid Vehicles

A novel, active cell balancing circuit and charging strategy in lithium battery pack is proposed in this paper. The active cell balancing circuit mainly consists of a battery voltage measurement circuit and switch control circuit. First, all individual cell voltages are measured by an MSP430 microcontroller equipped with an isolation circuit and a filter circuit. Then, the maximum cell voltage difference is calculated by subtracting the minimum cell voltage from the maximum cell voltage. When the maximum cell voltage difference exceeds 0.05 V, the balancing action starts to carry on. The MSP430 microcontroller output controls signals to close the switches corresponding to the battery cell with the maximum voltage. At this time, the balancing charge power performs a balancing charge for other batteries, except for the one that is switched on. In addition, a three-stage balancing charge strategy is also proposed in this paper to achieve the goal of speedy charging with balancing action. In the first stage, a 0.5 C balancing current is used to perform pre-balanced charging on all battery cells until the maximum cell voltage difference is less than 0.05 V, which is required for entry to the second stage of charging. In the second stage, constant current charging of 1 C, coupled with 0.2 C balancing current charging is carried out, until the maximum battery cell voltage reaches 4.2 V, which is required for entry into the third stage of charging. In the third stage, a constant voltage charging is coupled with 0.2 C balancing current charging, until the maximum battery cell voltage reaches 4.25 V, which is required to complete the balancing charge. The imbalance of power between the battery cells during battery pack charging, which reduces battery charging efficiency and battery life, is thus effectively improved. In this paper, a six-cells-in-series and two-in parallel lithium battery pack is used to perform a balancing charge test. Test results show that the battery cells in the battery pack are capable of quickly completing a balancing charge under different initial voltages, the maximum voltage difference is reduced to within the range of 0.05 V, and the total time required for each balancing charge is approximately 3600 s.

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Simplified Extended Kalman Filter Observer for SOC Estimation of Commercial Power-Oriented LFP Lithium Battery Cells

10.4271/2013-01-1544 ◽

2013 ◽

Cited By ~ 18

Author(s):

Tarun Huria ◽

Massimo Ceraolo ◽

Javier Gazzarri ◽

Robyn Jackey

Keyword(s):

Kalman Filter ◽

Extended Kalman Filter ◽

Lithium Battery ◽

Soc Estimation ◽

Battery Cells

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An Active and Passive Hybrid Battery Equalization Strategy Used in Group and between Groups

Electronics ◽

10.3390/electronics9101744 ◽

2020 ◽

Vol 9 (10) ◽

pp. 1744

Author(s):

Mingyu Gao ◽

Jifeng Qu ◽

Hao Lan ◽

Qixing Wu ◽

Huipin Lin ◽

...

Keyword(s):

Lithium Battery ◽

Bottom Layer ◽

Equilibrium Strategy ◽

Forward Converter ◽

Flyback Converter ◽

Equilibrium Strategies ◽

Simulation And Experiment ◽

Series Of Experiments ◽

Battery Cells

Active battery equalization and passive battery equalization are two important methods which can solve the inconsistency of battery cells in lithium battery groups. In this paper, a new hybrid battery equalization strategy combinfigureing the active equalizing method with a passive equalizing method is proposed. Among them, the implementation of the active equalizing method uses the bidirectional Flyback converter and Forward converter. This hybrid equalizing strategy adopts the concept of hierarchical equilibrium: it can be divided into two layers, the top layer is the equalization between groups, and the bottom layer is the equalization of group. There are three active equilibrium strategies and one passive equilibrium strategy. For verification purposes, a series of experiments were conducted in MATLAB 2018b/Simulink platform. The simulation and experiment results show that this hybrid battery equalizing method is efficient and feasible.

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Switched Energy Management Strategy for Fuel Cell Hybrid Vehicle Based on Switch Network

Energies ◽

10.3390/en13010247 ◽

2020 ◽

Vol 13 (1) ◽

pp. 247 ◽

Cited By ~ 3

Author(s):

Xu Chen ◽

Guangdi Hu ◽

Feng Guo ◽

Mengqi Ye ◽

Jingyuan Huang

Keyword(s):

Fuel Cell ◽

Energy Management ◽

Management Strategy ◽

Lithium Battery ◽

Hybrid Vehicles ◽

Battery Pack ◽

Normal Operation ◽

Power Demand ◽

Energy Management Strategy ◽

Capacity Degradation

Environmentally friendly and pollution-free fuel cell/lithium battery hybrid vehicles have received the attention of the community in recent years. It is imperative for fuel cell/lithium battery hybrid vehicles to use the energy management strategy (EMS) to distribute the output power of each power source to improve fuel economy and system life. In practical application, inconsistency of battery pack will lead to security hazard and capacity degradation. However, few EMS take the inconsistency of battery pack into account. Also, the current battery equalization strategy rarely discusses how to perform the equilibrium process while meeting the power demand of vehicle. To solve these issues, a novel equalization energy management strategy (EEMS) based on the switch network is proposed at first. Then, a switched energy management strategy (SEMS) that switches between the EEMS and the equivalent consumption minimization strategy (ECMS) is proposed and implemented in the fuel cell/lithium battery hybrid system to validate its effectiveness. The results show that the proposed SEMS can ameliorate the inconsistency of series lithium battery pack while meeting the power demand of vehicle’s normal operation. It can improve the safety and durability of the system and reduce the equalization time. Besides, it has good expansibility and no energy waste.

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