The application areas of batteries are currently booming. The recent generation of devices combines a high energy density with a reasonable cost and life expectancy, making them suitable not only for cars but also electric bikes, scooters, forklifts, gardening and household tools, storage batteries as well as airborne applications such as drones, helicopters, and small airplanes. Since manufacturing batteries requires a lot of energy and minerals, extending the life of the battery is worthwhile from both an ecologic and an economic point of view. The use of Battery Management Systems (BMS) can extend battery life, if they are used with a sound understanding of the internal electrical processes. This book provides insight into the electric behaviour of batteries for researchers involved with the design of battery management systems, and experts involved with electric vehicle development. It covers a range of options for designing battery management and cell balancing systems, with a focus on inductive balancing. After an overview of previous and current battery types, chapters convey a number of cell-balancing techniques, such as passive and active equalizer circuits, with a focus on transformer and coupled inductor based balancing methods. In addition, cell voltage monitoring and charging are investigated. Furthermore, solutions are provided to reduce the number of inductive components, the number of windings, and practical implementation.
Inspec keywords: lithium compounds; DC-DC power convertors; battery management systems; secondary cells; power transformers; battery powered vehicles
Other keywords: lithium compounds; inductive balancing; electrochemical electrodes; electric vehicle charging; battery powered vehicles; power transformers; electric vehicles; DC-DC power convertors; battery management systems; secondary cells; battery chargers
Subjects: Secondary cells; General electrical engineering topics; Handbooks and dictionaries; Education and training; Transformers and reactors; Monographs, and collections; General transportation (energy utilisation); Textbooks; Secondary cells; Power electronics, supply and supervisory circuits; Transportation
This paper is about the term 'cell' is the smallest individual electrochemical unit. It delivers a voltage that depends on the mixture of chemicals and compounds chosen to make the cell.The electrochemical unit is characterized by an anode 'negative electrode' and a cathode'positive electrode'. The batteries for electric vehicles (EV) mainly include lead-acid, nickel-metal hydride,and lithium-ion batteries. Lithium-ion batteries possess very low self-discharge rates compared to other battery types. They have no memory effects, which means it can be charged and discharged more flexibly than other types. For instance, in lead-acid cells, whenthe fully charged state voltage is reached, it provides some inherent balancing function as the leakage current increases. In contrast, lithium-ion batteries cannot be operated in this way. They lead to overcharging, causing internal corrosion and unsafe operating conditions
In general, only mentioning the positive aspects may be a way to write a book. However, most technologies have disadvantages or some weakness aspects, so also batteries. Being open to a discussion may even a way to improve the battery development and the battery management system (BMS). What is a problem today could be solved a few years after, each day discoveries are made, but only a fraction of 1% gets to the market. Most of the battery news is a small increment in a bigentity. We have seen a similar evolution in PV panels, gradually less (fossil) energywas needed to manufacture, and less critical materials for the same power. Aboutnine elements can be enumerated in a battery: cathode conductor, cathode materials, cathode electrolyte, separator (membrane), anode electrolyte, anode materials, anode conductor, housing, and BMS. So if even for lithium, for each, ten different techniques are considered, the theoretical total count is 109 possibilities. They cannot all be combined, but the effort and skills of many engineers and designers will be needed to land on really effective technologies for all aspects
Since the invention of the older battery types, during one century mainlyimprovements happened to existing types. However, in the last decades we can saythat some revolution occurred. This is mainly as types were not only developedwith non-water-based electrolytes, but also with the right use of membranes toseparate the anode and cathode chemistry. This not only allowed increasing the cellvoltage but also the use of lighter ions as active material. In the meantime, anotherthing happened that the ion-based batteries did not show any increased leakagecurrent at high voltage but instead deteriorated gradually or had safety problems.This initiated the need for battery management systems (BMSs) that had to monitoreach cell to keep it between limits in voltage. Further, new materials were devel-oped and gradually become affordable, such as ceramic materials, carbon fibre,graphene, silicon, a choice of organic electrolytes, and also more (power-) elec-tronic control. The result is a technology that reaches much more energy and powerdensity than before. Research also improved the understanding of ageing, so thatthe number of cycles increased. All these things opened new application areas; firstin smaller appliances such as mobile phones, then computer, tools, all kinds ofvehicles, grid storage.
Batteries are widely used as the common electrical energy storage device in vehicles as a replacement of traditional fossil fuels. The capacity of the battery is gradually reduced due to erosion, passivation, outgassing, decomposition of materials, and changes on the electrode surface during its operation. The aim is to guarantee the safe operation and a long life of a battery. It helps to know the battery state, which simply can be described by two parameters: State of Charge (SoC) and State of Health (SoH). The SoC mostly depends on the current from and towards the battery, and its initial charge condition at a given temperature. The series-connected lithium-ion batteries should be controlled and monitored by an effective Battery Management System (BMS). A BMS can protect the battery from damage, predict battery life, and maintain battery operation for offering high performance. The main goal of a BMS is to minimize the imbalance within the pack toextend the life of the batteries and to obtain the highest performance. Reducing the wasted energy in a passive balancing method could have a significant effect on the energy throughput of the battery system.
In this chapter, an equalizing and monitoring system for an ultra-light electric vehicle is investigated. It permits to pin important information if one cell is high, charging should be limited to some trickle charge, and if all cells are high to stop charging. The proposed monitoring system detects if one cell is fully charged or all cells are fully charged and the equalizing system tops each cell at the desired voltage. To this issue, a light-emitting diode (LED) bandgap is used, as a voltage reference, another LED is used to inform the user if any cell is at its high voltage. A smart monitoring displays a text message on the liquid crystal display (LCD) screen, if one cell is high or all cells are high. This detection also provides a signal to the microcontroller to turn on/off the charger if all cells are high. Also, a Bluetooth module is designed to command the microcontroller to turn on/off the charger via voice/text message by using a smartphone. A major feature of the system is to draw a very low standby current, so that the system does not contribute significantly to the self-discharge of the battery.
This paper is based on a resonant switched-capacitor converter(RSCC) balancing technique. It equalizes eight numbers of cells in a series. In Li-ion batteries, voltage differences always exist between cells due to the charging and discharging process; therefore, a battery management system is required to ensurethat all cells are equally charged or discharged and it also increases the life time of the battery. An equalizing method is essential to achieve the best performance.A number of cell balancing methods have been presented. Among the active balancing topologies, the switched-capacitor converter (SCC) is popular as it can be partly integrated in IC technology.They use only capacitors in the power stage for power storage and transferring energy.
A special Cuk converter balancing circuit for lithium-based batteries is investigated. In an electric vehicle and a lot of battery appliances, batteries play an important role due to the fact that the cost depends on the batteries; thus the batteries with a longer life cycle are desired. Therefore, a battery management system is required to increase the life cycle of the batteries. In batteries, the cell voltages will differ due to the charging and discharging process; thus a balancing circuit is needed to ensure that all cells are at the same voltage level. Among existing cell balancing methods, Cuk converter balancing has a feature of fast balancing time and fewer costs. In this chapter, eight cells in series in a battery pack are considered. This method uses only N switches per N cells. All switches are N-channel MOSFETs (lowRDS(on)), with body diodes, and they are triggered with PWM in synchronous patterns with 50% duty cycle. It is an advantage that the number of components is reduced, so reducing losses. The proposed circuit is tested with significant cell voltage differences to have voltage imbalances in order to verify the proposed topology. The simulation results are performed to testify the variability of the proposed circuit.
This chapter develops a coupled inductor balancing method to overcome cell voltage variation among cells in series, for lithium-ion (Li-ion) batteries with applications in electric vehicles, and a lot of other today uses. In this book, we call the principle 'coupled inductor' balancing when the magnetic device has all the same number of turns. The term 'transformer' is used when there is a primary winding using a higher number of turns. Two variants will be proposed in the three different parts. The first variant proposes a circuit with two cells per winding. The second uses a Cuk converter principle.
The concept of an active cell balancing technique, based on multi-winding transformer balancing for lithium-ion (Li-ion) batteries is presented. In Li-ion-based batteries, voltage differences exist between cells due to the charging and discharging process; thus, a battery management system is required to ensure that all cells are equally charged or discharged. An equalizing method is essential to achieve the best performance. Several cell balancing methods have been presented. Among them, the multi-winding transformer balancing method has fast equalization time and is easy to control. The proposed method uses MOSFETs as a switch in the output and a single phase full bridge at the input. Suppressing diodes results in lower losses and has a faster response. Be aware that the output transistor conducts when the input is also on, so it is a forward configuration. Fast equalization, easy to control, high efficiency and easy isolation are its features. Unlike the forward structure, the proposed method does not use a demagnetizing winding or resistor-capacitor-diode circuit in order to demagnetize the primary winding. The simulation results are performed to verify the feasibility of the system.
In this chapter, the concept of a forward balancing technique fed by a buck con-verter for lithium-based batteries in electric vehicle applications is investigated. The proposed active topology equalizes eight cells in a series in a battery pack, by using a forward converter for each battery pack, and the whole battery packs, using a buck converter. The battery bank consists of four battery packs which are in series. Therefore, the proposed system will equalize 32 cells in series as an example. In this chapter, the proposed circuit employs a single transistor used in azero-voltage switch (ZVS) for the forward converter. In practice, it means that a capacitor in parallel with the switch at the same time helps to obtain a demagnetizing of the transformer without excessive voltage on the transistor.
This chapter presents the concept of charging of lithium-iron-phosphate (LFP)battery cells in an electric vehicle (EV). An example of an ultralight EV has beentaken, but many of the concepts can be enlarged to many other vehicles types or appliances. Charger topologies play an important role in EVs to increase the performance of the batteries.
The section proposed a selection of current between full charge and a current limited trickle charge. If the current is always limited, it would result in avery long charging time. To overcome this problem, two-stage charging is proposed. First, mostly much more than 90% of the battery capacity could becharged using higher currents (6 A). Then the remaining part, much less than 10% of the capacity is then charged using limited current (300 mA). If 1% ofthe charge has to be equalized, it could take about 1 h. However, very long equalizing times could happen if a repair has been done, which could save the battery by doing this. The proposed circuit is only one possible design, other variants can be imagined, but the circuit is a check if the necessary actions are implemented.
The aim of this chapter is to charge the batteries with PV panels on the vehicle roof, or panels independent from grid, or on the car port. Today, most of DC charging is designed for massive power, for fast charging. However, the tiny power from PV may finally be the most cost-effective one. The maximum power point voltage of this PV panel is much lower than the battery packs; thus a DC-DC converter is needed to overcome this problem. Therefore, a push-pull converter is designed and implemented to be connected to the solar panel. As the trial was at a small vehicle, the main aim was simplicity. The batteries are lithium-iron-phosphate (LFP) battery. The batteries are connected in series with a total number of 32 cells. The battery bank includes four battery packs and each pack consists of eight cells in series. The operational principle of the circuit is explained, and the experimental results are performed to verify the feasibility of the proposed system.
In this paper is about 'two-stage DC/DCconverter' is to equalize all battery cells from the total battery packs. In the firststage, the first converter, which is a buck converter, will be fed by the total battery pack consisting of four packs in series. Also, each pack includes 8 cells in series,thus a total of 32 cells in series. The nominal voltage of each cell is 3.2 V in thiscase; therefore, the total pack results in 102.4 V. The first converter 'buck con-verter' [1] will decrease the total battery packs voltage to a lower voltage, forexample 40 V, which is suitable to feed the second-stage converter to equalize eight cells in series.