Dynamic equalization techniques for series battery stacks
06 Oct 1996-pp 514-521
TL;DR: In this article, the authors present, discuss and evaluate the different techniques proposed to achieve individual cell equalization for series battery stacks, and evaluate different techniques for series connected battery stacks is not as straightforward.
Abstract: Secondary battery life can be dramatically improved if the charging process can be regulated to prevent gassing and overcharging. This can be achieved by controlling the battery charging rate especially near the end of the charge cycle. Different charging algorithms have been devised to achieve this goal for individual battery modules. However, extending these algorithms to series connected battery stacks is not as straightforward. Normal differences in cell chemistries and temperature gradients along a battery stack can lead to large nonuniformities in cell charge levels. Maintenance of cells at an equalized charge level is critical for enhancing battery life. Different systems and schemes have been proposed to attain this goal. This paper presents, discusses and evaluates the different techniques proposed to achieve individual cell equalization for series battery stacks.
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TL;DR: In this article, a brief introduction to the composition of the battery management system (BMS) and its key issues such as battery cell voltage measurement, battery states estimation, battery uniformity and equalization, battery fault diagnosis and so on, is given.
3,650 citations
TL;DR: In this paper, the authors comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques, and discuss the advantages and disadvantages of these voltage boosting techniques and associated converters.
Abstract: DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.
1,230 citations
Cites background from "Dynamic equalization techniques for..."
...power individually, which will increase the overall charging system efficiency [25]–[27], [238]....
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TL;DR: The proposed battery equalization scheme is a bidirectional dc-dc converter with energy transferring capacitor that can be designed as a ripple-free converter for improving the input current distortion of the battery charge supply power system.
Abstract: An intelligent battery equalization scheme based on fuzzy logic control is presented to adaptively control the equalizing process of series-connected lithium-ion batteries. The proposed battery equalization scheme is a bidirectional dc-dc converter with energy transferring capacitor that can be used to design the bidirectional nondissipative equalizer for a battery balancing system. Furthermore, it can be designed as a ripple-free converter for improving the input current distortion of the battery charge supply power system. A fuzzy-logic-controlled strategy is constructed with a set of membership functions to prescribe the cells equalizing behavior within a safe equalizing region for rapid cell voltage balancing. The simulation and experimental results show the advantage of the predicted equalizing performance of the lithium-ion battery stacks. The proposed fuzzy logic control battery equalization controller can abridge the equalization time about 32%. The proposed method maintains safe operation during the charge/discharge state in each lithium-ion cell of the battery strings.
519 citations
Cites background from "Dynamic equalization techniques for..."
...The nondissipative current diverter battery equalization scheme can be classified into unidirectional and bidirectional approaches [4], [6]....
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TL;DR: In this paper, a quasi-resonant ZCS (QRZCS) based battery equalization scheme was proposed for dc-to-dc dc converter with an individual cell equalizer.
Abstract: A systematic approach to reform and analyze a soft-switching bidirectional dc-to-dc converter is proposed for cell voltage balancing control in a series connected battery string. quasi-resonant converter circuits have been designed to achieve the zero-current-switching (ZCS) to reduce the switching loss in bidirectional battery equalizers. The results indicate that the switching loss and energy transfer efficiency can be substantially improved using the quasi-resonant ZCS (QRZCS) technology in a battery charging system with an individual cell equalizer (ICE). The validity of the battery equalization is further verified using an experimental installation involving a battery string of three lithium-ion cells. The simulation and experimental results show that the proposed QRZCS battery equalization schemes can achieve bidirectional battery equalization performance and reduce the MOSFET transistor switch power losses by more than 96% and increase the efficiency by around 20%~30% compared with the conventional battery equalizer during an identical equalization process
375 citations
13 Oct 2011
TL;DR: In this article, a review and comparison between the different cell balancing topologies for battery string based on MATLAB/Simulink® simulation is presented, according to circuit design, balancing simulation, practical implementations, application, balancing speed, complexity, cost, size, balancing system efficiency, voltage/current stress, etc.
Abstract: Battery systems are affected by many factors, the most important one is the cells unbalancing. Without the balancing system, the individual cell voltages will differ over time, battery pack capacity will decrease quickly. That will result in the fail of the total battery system. Thus cell balancing acts an important role on the battery life preserving. Different cell balancing methodologies have been proposed for battery pack. This paper presents a review and comparisons between the different proposed balancing topologies for battery string based on MATLAB/Simulink® simulation. The comparison carried out according to circuit design, balancing simulation, practical implementations, application, balancing speed, complexity, cost, size, balancing system efficiency, voltage/current stress … etc.
371 citations
Cites background or methods from "Dynamic equalization techniques for..."
...In addition, by [5] since the switching frequency is quite high, filter capacitors must be placed across each battery to filter the high frequency....
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...Quite a lot of cell balancing/equalization methods have been proposed such [1-34] and reviewed in [1-5]....
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...The resistor element will be either in fixed mode as [5-6] or switched according the system as [1-5], [7-9]....
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References
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TL;DR: A straightforward means of embedding equalization within an outer-loop supervisory control that maintains a fast charging rate while providing overall protection against overcharging is briefly described.
Abstract: The primary difficulty in charging storage batteries is in attaining process regulation that allows fast charging while avoiding destructive overcharging. A two-level approach to controlling the charging process is presented. A general background discussion of batteries and charging problems is followed by the presentation of a novel recirculating charge equalization technique that enhances the uniformity of batteries made up from long serial strings of cells. A straightforward means of embedding equalization within an outer-loop supervisory control that maintains a fast charging rate while providing overall protection against overcharging is briefly described. Simulation and experimental results confirm the applicability of the equalization control technique. >
229 citations
05 Mar 1995
TL;DR: In this article, the authors proposed a new charge equalization technique for a series string of battery cells, which utilizes a simple isolated DC-to-DC power converter with a capacitive output filter along with a multi-winding transformer.
Abstract: Charge equalization for series connected battery strings has important ramifications on battery life. It enhances the uniformity of the battery cells and hence improves the life of the battery as a whole. A new charge equalization technique for a series string of battery cells has been recently proposed by the authors. The basic technique utilizes a simple isolated DC-to-DC power converter with a capacitive output filter along with a multi-winding transformer. The possibility of integrating the trickle charge function with the charge equalization function is potentially very attractive, as it can lead to an efficient and low cost implementation. >
204 citations
02 Oct 1994
TL;DR: In this paper, a simple technique that provides charge equalization for a series string of battery cells is presented, which utilizes a simple isolated DC/DC converter with a capacitive output filter along with a multi-winding coaxial winding transformer (CWT).
Abstract: A simple technique that provides charge equalization for a series string of battery cells is presented. The advantages of accurate charge equalization are very substantial and include reduced damage to battery cells in the stack, and a dramatic increase in battery life. The basic technique utilizes a simple isolated DC/DC converter with a capacitive output filter along with a multi-winding coaxial winding transformer (CWT). The coaxial winding transformer is known for its low and controlled leakage inductance. The transformer leakage inductance is used as the main driving impedance to control the total charging current for the individual cells. The use of one low-power converter to obtain charge equalization for the entire battery string is very attractive and leads to a low cost implementation. >
196 citations
05 Nov 1991
TL;DR: The individual cell voltage equalizer (ICE) as discussed by the authors is a two-terminal voltage-controlled current shunt that provides each cell with an alternate current path for string float current.
Abstract: The individual cell voltage equalizer (ICE) is a two-terminal voltage-controlled current shunt. The ICE unit is connected to the positive and negative terminals of each cell in a battery string. ICE provides each cell with an alternate current path for string float current. Using ICE makes it possible to check battery cells by using a simple digital voltmeter, when cell voltages deviate by more than +or-0.05 V per cell and capacity testing or replacement is required. ICE was designed to monitor and control individual cells in stationary battery strings. ICE monitors cell voltages and acts as current shunt by allowing current to bypass cells with high voltages. Conversely, current will pass through low voltage cells to bring voltage back to the current level. ICE was designed with limited shunting ability. Thus, weak cells are identified before failure. The result is timely and orderly cell replacement. >
149 citations
Patent•
21 Jun 1993
TL;DR: In this paper, a battery charger is described for recharging reusable batteries in a manner that prevents overcharging of the same, including a voltage source and non-dissipative shunt arrangement that can be customized to charge any number of batteries.
Abstract: A battery charger is disclosed for recharging reusable batteries in a manner that prevents overcharging of the same. The charger includes a voltage source and non-dissipative shunt arrangement that can be customized to charge any number of batteries. The charger may be a current limiting power supply that is controlled by the voltage or charge state of the batteries being recharged. The non-dissipative shunt includes a pair of transistors for each pair of batteries and an inductor placed one end between the battery pair and another end between the transistor pair. An oscillator, having two phases of equal, but opposite phase, is used to control each transistor to apply charge to a given battery during one phase and then to allow the charge to equalize between the battery pair during the second phase. The equalization is continued until both batteries reach a full charge without overcharging any one battery.
128 citations