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In this paper, the ac impedance analysis is used to explore the optimal discharging frequency for a Li-ion battery. Experiments indicate that the optimal discharging frequency is at the minimum ac impedance frequency fZmin for a conventional pulse-current (PC) discharging. In addition, a sinusoidal current (SC) discharging strategy is also proposed to achieve better performances. This SC discharging strategy improves the discharging capacity, discharging efficiency, and rising temperature of the Li-ion battery by about 1.3%, 1.32%, and 41.9%, respectively, as compared with the traditional constant-current discharging.

In this paper, a single-phase multilevel inverter with battery balancing is proposed. The input of each individual inverter is directly connected to a battery. The combination of batteries can be controlled according to the batteries' voltages to implement the battery-balancing function. The operational principle of the proposed system is first described, and then, the design equation is derived. Experiments show that the battery-balancing discharge function is achieved. Finally, a prototype is designed and implemented to verify the feasibility and excellent performance.

In this paper, the sinusoidal-ripple-current (SRC) charging strategy for a Li-ion battery is proposed. The ac-impedance analysis is used to explore the optimal charging frequency. Experiments indicate that the optimal charging performance can be achieved by the proposed SRC with the minimum-ac-impedance frequency fZmin. Compared with the conventional constant-current constant-voltage charging strategy, the charging time, the charging efficiency, the maximum rising temperature, and the lifetime of the Li-ion battery are improved by about 17%, 1.9%, 45.8%, and 16.1%, respectively.

In this paper, a phase-locked bidirectional converter (BC) (PLBC) with pulse charge function is proposed to improve the battery charge efficiency. The circuit topology of the proposed PLBC is the same as that of the current-pump phase-locked loop (CP-PLL). Using CP-PLL inherent characteristics, a pulse current with bidirectional flow can be automatically implemented. A design example for a 42-V/14-V dual-voltage PowerNet is built to assess the PLBC's performance. Compared with the conventional BC, the battery charge efficiency ηb is improved by about 2.8%. Moreover, the battery increased temperature is reduced by about 5.7 °C simultaneously.

In this paper, a resistance-compensated phase-locked battery charger (RC-PLBC) mathematical model is built, and its s-domain transfer function is also derived. The stable, safe, and nonovercharging conditions of the RC-PLBC are discussed, and many criteria are proposed. After that, a complete design procedure is presented for designing a fast and safe RC-PLBC. A prototype of RC-PLBC is designed and realized to verify the charging performance. Comparing with a typical PLBC, the charge speed of the proposed RC-PLBC is improved by 18%, and the safety is held on.

In this paper, a duty-varied voltage pulse-charge strategy (DVVPCS), that can detect and dynamically track the suitable duty of the charge pulse, is proposed to improve the battery-charge performance. To assess the system performance, a prototype of the duty-varied voltage pulse charger (DVVPC) is designed and implemented. Comparing with the standard constant-current and constant-voltage (CC-CV) charge strategy, the charge speed of the proposed DVVPCS is improved by about 14%, while the proposed DVVPCS is improved by about 5% in comparison with the conventional duty-fixed voltage pulse-charge strategy (DFVPCS). The charge efficiency of the proposed DVVPC has been improved by about 3.4% as compared with that of the general CC-CV. In comparison with conventional DFVPCS with D = 50%, the charge efficiency of the proposed DVVPCS is improved by about 1.5%. The results indicate that the DVVPCS can actually provide pulse with suitable duty to charge the battery, and the charge performance is improved.

In this paper, we consider an Li-ion battery as a grey system. The grey prediction technique is then used to develop a grey-predicted Li-ion battery charge system (GP-LBCS). The proposed GP-LBCS is designed to replace the general constant-voltage (CV) mode using the GP mode to improve the Li-ion battery charge behavior. A GP algorithm is built in GP-LBCS to make the charge trajectories faster and safer. A 3-D Y-mesh diagram for describing the charge trajectories of the proposed GP-LBCS is simulated. A GP-LBCS prototype is designed and implemented to assess the charge performance. Experiments show that the charge speed and the charge efficiency of the proposed GP-LBCS, compared with the general constant-current-CV charge system, are increased above 23% and 1.6%, respectively. The charge speed and efficiency in the proposed GP mode are improved above 34% and 7%, respectively, compared with that in the general CV mode.

In this paper, a reflex charging strategy with the energy recovery function for a bidirectional converter (BC) is proposed to build a novel reflex-based BC (RBC) for increasing the battery charging efficiency in an uninterruptible power supply (UPS). The proposed RBC can provide a reflex charging current profile to charge the battery to obtain a high battery charging efficiency and prolong the battery life cycle. In particular, the negative pulse energy of the reflex charging current profile in the proposed RBC is recovered to reduce the battery charging dissipation. A soft transfer method is also developed in this paper to really erase the spike current in the RBC. A 400 W prototype is designed and implemented to verify the feasibility of the proposed RBC. Compared with a typical bidirectional converter, the battery charging efficiency, the battery charging speed, and the battery thermal deterioration effect are improved by about 10%, 8.8%, and 7%, respectively, with the proposed RBC.

A novel current-pumped battery charger (CPBC) is proposed in this paper to increase the Li-ion battery charging performance. A complete charging process, consisting of three subprocesses, namely: 1) the bulk current charging process; 2) the pulsed current charging process; and 3) the pulsed float charging process, can be automatically implemented by using the inherent characteristics of current-pumped phase-locked loop (CPLL). A design example for a 700-mA ldr h Li-ion battery is built to assess the CPBC's performance. In comparison with the conventional phase-locked battery charger, the battery available capacity and charging efficiency of the proposed CPBC are improved by about 6.9% and 1.5%, respectively. The results of the experiment show that a CPLL is really suitable for carrying out a Li-ion battery pulse charger.

In this paper, a variable frequency pulse charge system (VFPCS), that can detect and dynamically track the optimal charge frequency, is proposed to improve the battery-charge response. To assess the system performance, a prototype of the VFPCS for 600-mAh lithium-ion battery is designed and implemented. Compared with the standard constant-current and constant-voltage charge system, the charge speed of the proposed VFPCS is improved above 24%, while the proposed VFPCS is improved above 10% compared with the conventional fixed-frequency pulse charge system. The results indicate that the VFPCS can actually provide pulse with optimal frequency to charge the battery and the charge response is improved

A fuzzy-controlled active state-of-charge controller (FC-ASCC) for improving the charging behavior of a lithium-ion (Li-ion) battery is proposed. The proposed FC-ASCC is designed to replace the general constant-voltage charging mode by two kinds of modes: sense and charge. A fuzzy-controlled algorithm is built with the predicted charger performance to program the charging trajectory faster and to keep the charge operation in a proposed safe-charge area (SCA). A modeling work is conducted for analyzing and describing the Li-ion battery in charging process. A three-dimensional Y-mesh diagram for describing the charging trajectories of the proposed FC charger is simulated. A prototype of a Li-ion battery charger with FC-ASCC is simulated and realized to assess the predicted charging performance. Experiment shows that the charging speed of the proposed FC charger compared with the general one increases about 23% and the charger can safely work in the SCA.

In this paper, a phase-locked battery charger (PLBC) is proposed to show that a phase-locked loop (PLL) is a perfect circuit topology for battery charging. The circuit topology of the PLBC is almost the same as that of the PLL and it inherits the merits of the PLL, such as autotracking, autolocking, and high accuracy. A complete charging process, consisting of three subprocesses: constant current charge, variable current charge, and float charge, can be automatically implemented by using the above inherent characteristics of the PLL. Experimental results show that the PLL is really suitable for carrying out a battery charge controller.