This paper proposes a novel online insulation fault detection circuit to overcome the shortcomings of ungrounded DC power supply system for being unable to provide high sensitivity leakage current detection. In this paper, the capacitor group is used to connect with positive and negative bus and ground the intermediate point of the capacitor group, and that each branch loop is installed with a leakage current detection device. When insulation fault occur in the system, the capacitor is able to provide a leakage current return path and discharge through the stored energy in the capacitor. This will allow the Hall effect current sensor to detect the difference of positive and negative bus current, and deliver warning signal or control the breaker to cut off the power supply. The experiment result demonstrates that this novel method is able to detect 1mA/50kΩ insulation fault to achieve the high sensitivity detection goal.
Battery cost and battery capacity are key factors to determine whether or not electric vehicles would be used widely. Having a high energy density, lithium-ion battery can improve the mileage range of electric vehicles, yet the battery cost remains high. Although lead-acid battery has lower energy density than that of lithium-ion batteries, lead-acid battery cost less. Moreover, lithium-ion battery features an excellent discharge characteristic, whereas load current significantly impacts the capacity of lead-acid battery. This paper proposes a novel scheme to improve the efficiency of electric vehicle battery. In addition to connecting lead-acid battery with lithium-ion battery in parallel to the power supply, the proposed method combines their discharge characteristics to optimize the power management in order to improve the efficiency of attery and lower the cost of electric vehicle battery. The experimental result demonstrates that the available capacity can improve 30~50% of the rated capacity of the lead-acid battery.
This paper proposes a smart lithium-ion battery capacity estimation method for electric bicycles. Battery capacity information informs the electric vehicle driver of the residual battery working time, thus facilitating the estimation of mileage of electric bicycle and timing of battery charging to avoid overcharging or over-discharging. Factors such as different discharge rates, environmental temperature, battery charge and discharge efficiency and battery aging affect the released capacity of battery, which is an electrochemical reaction of battery. In addition to integrating the advantages of the coulometric measurement and open circuit voltage measurement methods, and the proposed smart lithium-ion battery capacity estimator also incorporates discharge current, temperature, battery aging, as well as charging efficiency factors into capacity correction to develop a highly accurate PIC single-chip lithium-ion battery capacity estimation system.
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