Abstract
This paper proposes an improved fast charging strategy for electric vehicles (EVs) by considering available battery capacity. According to previous research and battery experiment reports, the energy capacity of batteries is not fixed, and it can decrease temporarily depending on the magnitude of charging or discharging power. This paper addresses the decreased capacity in proportion to the magnitude of the charging power which leads to a reduction in the driving range. For effective and practical use for EV users, the change in battery capacity is expressed through an equation, and a new state of charged indicator is proposed. To improve the conventional charging method that uniformly supplies power regardless of the battery capacity, this paper proposes an optimal charging strategy injecting constant power. The proposed charging strategy provides an optimal charging power reference to minimize costs considering charged energy, charging time, and usable energy loss based on billing system of EV charging. To verify the effectiveness of the proposed charging method, the optimal charging power reference for each battery is calculated based on capacity and characteristics, and the total cost is compared. The results show that the performance of the proposed charging strategy is effective in minimizing both the reduced battery capacity and economic burden on EV users.
Highlights
Environmental issue such as global warming are becoming increasingly important, and electric vehicles (EVs) using secondary batteries are presented as a solution to replace fuel sources and gas emission from vehicles
This paper suggests the constant power constant voltage (CPCV) method with optimal power references that fit each capacity of battery and the associated coulombic efficiency characteristics [6]
Most EV battery research has focused on the exothermic reaction or voltage balancing and coulombic efficiency
Summary
Environmental issue such as global warming are becoming increasingly important, and EVs using secondary batteries are presented as a solution to replace fuel sources and gas emission from vehicles. The previous studies and experimental results regarding discharge capacity in the electro-chemical characteristics are mathematically formulated and applied to the battery model. This paper suggests the constant power constant voltage (CPCV) method with optimal power references that fit each capacity of battery and the associated coulombic efficiency characteristics [6]. Other studies did not reflect the phenomenon that the amount of usable energy decreases because the magnitude of the charging power is too large for the capacity or characteristics of the battery. Their characteristics of charging methods are summarized and compared.
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