![]() Uncertainty in the knowledge of battery capacity. Such an approximation results in errors that increase with sampling interval as the load changes rapidly. Coulomb counting methods employ a simple, rectangular approximation for current integration. Current sensors are corrupted by measurement noise simple, inexpensive current sensors are likely to be more noisy and possibly biased. ![]() Since it is a recursive integration, any errors in the initial SOC assumption will remain as a bias. However, Coulomb counting method suffers from the following sources of errors: Figure 1a gives the approximate Coulomb counting equation that is used to compute SOC in a recursive manner. State of Charge EstimationĬoulomb counting is the easiest approach to estimate the state of charge (SOC) of a battery. Battery Management System: Goals and Challenges In this section, some of the challenges faced in designing battery BMS are briefly described. ![]() Finally, the paper is concluded in Section 4.Ģ. Section 3 describes some specific solutions developed by the authors in order to address the challenges faced by the present day battery management system. Section 2 describes in more details about the specific goals of a state of the art battery management systems and the challenges it needs to overcome. The present manuscript is written in the form of an expository paper detailing the many solutions developed by the authors in the recent past in order to address specific challenges in battery management systems. Considering the fact that the first use of the battery alters its electrochemical characteristics in unique ways, traditional BMS approaches that rely on empirical modeling, under the assumption that batteries of the same chemistry and size have similar characteristics, will be inadequate to manage used batteries. The state of the art BMS algorithms heavily depend on prior characterization carried out in laboratories Consequently, they are only effective for first time use of batteries. It is predicted that the electric vehicle sales are about to grow by nearly 500% in the next 10 years. Īn emerging challenge for battery management systems comes in the form of battery reuse. Individual cells in a battery-pack are known to become imbalanced over time causing safety and reliability issues short circuited cells are another common cause of safety and reliability issues in Li-ion batteries. BMS algorithms attempt to enhance efficiency of batteries in multiple ways optimal charging algorithms aim to reduce the amount of heat waste and the degradation of state of health precise SOC estimation algorithms will help to improve the efficiency by helping to design minimal battery-pack configurations based on specific needs. For example, charging efficiency is the percentage of the total energy needed during charing fast charging requirements results in significant energy waste in the form of heat. There are wide ranging issues affecting the efficiency of energy storage in batteries particularly, electric vehicle applications strive to improve efficiency in every possible way. The need to fast-charge the battery, which is important in electric vehicle applications, increases the possibility of thermal runaway and safety issues. Lithium ion batteries are susceptible to thermal runaway which is an irreversible chemical process triggered by several conditions including over-voltage and high temperature. The research challenges faced by the present day BMS are three pronged: safety, efficiency and reliability. However, most practical systems adopt the electrical ECM based approaches due to their simplicity. Two schools of approaches for battery management systems have emerged over time one models the battery through electrical equivalent circuit model (ECMs) and the other seeks to model it through electrochemical models. ![]() However, there are challenges remaining and in this paper we describe a list of challenges and outline possible solutions. Research on BMS has been very intense in the last two decades and significant improvements were achieved in the safety, efficiency and reliability of battery systems. A battery management system (BMS) ensures the safety, efficiency and reliability of a battery powered system. In addition to EVs, rechargeable batteries have been widely adopted in portable electronic equipment, household appliances, power tools, aerospace equipment and renewable energy storage systems. Rechargeable batteries promise a way to replace them by electric vehicles (EVs) in the near future. Automobiles powered by gasoline engines account for nearly 25% of the global energy consumption.
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