Technological advancement in storage systems has currently stimulated their use in miscellaneous applications. The devices have gained prominence due to their increased performance and efficiency, together with the recent global appeal for reducing the environmental impacts caused by generating power or by combustion vehicles. Many technologies have been developed to allow these devices to be reused or recycled. In this sense, the use of lithium-ion batteries, especially in electric vehicles, has been the central investigative theme. However, a drawback of this process is discarding used batteries. This work provides a short review of the techniques used for the second-life batteries of electric vehicles and presents the current positioning of the field, the steps involved in the process of reuse and a discussion on important references. In conclusion, some directions and perspectives of the field are shown.

In this paper, the switched-capacitor concept is extended to the voltage-doubler discontinuous conduction mode SEPIC rectifier. As a result, a set of single-phase hybrid SEPIC power factor correction rectifiers able to provide lower voltage stress on the semiconductors and/or higher static gain, which can be easily increased with additional switched-capacitor cells, is proposed. Hence, these rectifiers could be employed in applications that require higher output voltage. In addition, the converters provide a high power factor and a reduced total harmonic distortion in the input current. The topology employs a three-state switch, and three different implementations are described, two being bridgeless versions, which can provide gains in relation to efficiency. The structures and the topological states, a theoretical analysis in steady state, a dynamic model for control, and a design example are reported herein. Furthermore, a prototype with specifications of 1000-W output power, 220-V input voltage, 800-V output voltage, and 50-kHz switching frequency was designed in order to verify the theoretical analysis.

This paper extends the voltage-doubler concept to the single-phase SEPIC rectifier in discontinuous conduction mode and, as a consequence, novel rectifiers are proposed. A comparison with the classic SEPIC rectifier shows that the proposed converters can either provide reduced voltage stress on the semiconductors for the same output voltage level or supply double the gain of the output voltage with the same voltage stress. The proposed voltage-doubler SEPIC rectifiers provide a high power factor with no current control and they can be applied in order to improve the static gain of the structure, which can make the SEPIC rectifier suitable for applications that require a high voltage level. In this paper, the generic structure based on a three-state switch, four different implementations of the proposed concept (including bridgeless structures), steady-state analysis, a dynamic model, system control, and experimental results are presented. The proposed rectifiers were verified by experimental results obtained with a prototype built with the following specifications: 1000 W output power, 220 V input voltage, 400 V output voltage, and 50 kHz switching frequency. Peak efficiency of 95.84%, THD of 2%, and power factor of 0.9997 were obtained and, most importantly, double the gain of the output voltage was verified.

Recently, electric vehicles have gained enormous popularity due to their performance and efficiency. The investment in developing this new technology is justified by the increased awareness of the environmental impacts caused by combustion vehicles, such as greenhouse gas emissions, which have contributed to global warming and the depletion of oil reserves that are not renewable energy sources. Lithium-ion batteries are the most promising for electric vehicle (EV) applications. They have been widely used for their advantages, such as high energy density, many cycles, and low self-discharge. This work extensively investigates the main methods of estimating the state of charge (SoC) obtained through a literature review. A total of 109 relevant articles were found using the prism method. Some basic concepts of the state of health (SoH); a battery management system (BMS); and some models that can perform SoC estimation are presented. Challenges encountered in this task are discussed, such as the nonlinear characteristics of lithium-ion batteries that must be considered in the algorithms applied to the BMS. Thus, the set of concepts examined in this review supports the need to evolve the devices and develop new methods for estimating the SoC, which is increasingly more accurate and faster. This review shows that these tools tend to be continuously more dependent on artificial intelligence methods, especially hybrid algorithms, which require less training time and low computational cost, delivering real-time information to embedded systems.

This article reports the theoretical analysis and experimental results for a three-phase high power factor SEPIC-type rectifier operating in discontinuous conduction mode (DCM). The topology, steady-state analysis, dynamic model, control strategy, and experimental verification are reported herein. The operation in DCM naturally provides input currents with low harmonic content that are in phase with input voltages without the need for current control, due to the converter operation as a voltage follower. Thus, the control system and the PWM modulator are simplified, when compared to other three-phase high power factor rectifiers. The proposed three-phase SEPIC rectifier employs the voltage-doubler concept, which means it may reduce the voltage stress on the switches and diodes or it may supply double voltage gain with the same voltage stress. It also uses a three-state switch, and four different implementations are approached in this article, including bridgeless structures. The theoretical study was corroborated by experimental results obtained with a prototype built using the following design specifications: 220 V input voltage, 400 V output voltage, 3000 W output power, and 50 kHz switching frequency. Peak efficiency of 95.85%, THD of 3.1%, and power factor of 0.9991 were achieved.