Abstract
Estimating the residual capacity or state-of-charge (SoC) of commercial batteries on-line without destroying them or interrupting the power supply, is quite a challenging task for electric vehicle (EV) designers. Many Coulomb counting-based methods have been used to calculate the remaining capacity in EV batteries or other portable devices. The main disadvantages of these methods are the cumulative error and the time-varying Coulombic efficiency, which are greatly influenced by the operating state (SoC, temperature and current). To deal with this problem, we propose a lossy counting-based Coulomb counting method for estimating the available capacity or SoC. The initial capacity of the tested battery is obtained from the open circuit voltage (OCV). The charging/discharging efficiencies, used for compensating the Coulombic losses, are calculated by the lossy counting-based method. The measurement drift, resulting from the current sensor, is amended with the distorted Coulombic efficiency matrix. Simulations and experimental results show that the proposed method is both effective and convenient.
Highlights
State-of-charge (SoC) estimation is an important issue in the lithium-ion battery area
The state-switching will take up a very long time and its duration is tied to the state of SoC, temperature, and so on, so the open circuit voltage (OCV) method cannot be used for electric vehicle (EV) in driving status
From Equations (3)–(7) and Figure 3, we can see that the accumulated capacities of the lattices can be achieved by the proposed lossy counting method (LC)-based SoC estimation method, but the frequencies of different charge/discharge operations cannot be recorded by the proposed algorithm
Summary
State-of-charge (SoC) estimation is an important issue in the lithium-ion battery area. The state-switching (from an operating state to a balanced state) will take up a very long time and its duration is tied to the state of SoC, temperature, and so on, so the OCV method cannot be used for EVs in driving status To deal with this problem, researchers have developed several model-based SoC estimation methods, in which precise and complex battery models (the combing model, the Rint model, the ESC mode, etc.) were used for estimating the battery capacity [12,13,14]. The Coulombic efficiency is greatly influenced by the operating status of the battery (SoC, temperature and current) and this is difficult to measure [29,30,31,32] To deal with this problem, we propose a lossy counting-based relative Coulomb counting method for estimating the available capacity or SoC of lithium-ion batteries. We concluded this paper by highlighting the key contributions of this work
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