978-1-4799-8478-7/14/$31.00 ©2014 IEEE Development of Battery Management System for Cell Monitoring and Protection Irsyad Nashirul Haq #1 , Edi Leksono *2 , Muhammad Iqbal *3 , FX Nugroho Soelami *4 , Nugraha *5 , Deddy Kurniadi *6 , Brian Yuliarto *7 # Doctorate Student at Department of Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung Jalan Ganesha 10, Bandung 40132, Indonesia 1 inhprop@gmail.com * Department of Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung Jalan Ganesha 10, Bandung 40132, Indonesia 2 edi@tf.itb.ac.id, 3 m.iqbal@tf.itb.ac.id, 4 nugroho@tf.itb.ac.id, 5 nugraha@tf.itb.ac.id, 6 kurniadi@tf.itb.ac.id, 7 brian@tf.itb.ac.id Abstract— Battery has an important role as energy storage in electricity system utilization such as in electric vehicle and in smart microgrid system. Battery Management System (BMS) is needed to treat the dynamics of energy storage process in the battery in order to improve the performance and extend the life time of battery. In this paper, BMS cell monitoring and protection has been designed and tested for Lithium Ferro Phosphate (LFP) battery cells. The BMS cell monitoring function has been able to measure the battery parameters such as the voltage and current dynamics of each cell. The data taken from the BMS cell monitoring experiment is used to estimate the state of charge (SOC) of battery which is based on coulomb counting with coulomb efficiency ratios. The BMS cell monitoring function has successfully demonstrated the presence of unbalanced cell voltages during both processes of charging and discharging as well. From the analysis, the existence of capacity and energy fades was also investigated for every discharging and charging cycles. Based on the BMS cell protection experiment results, overcharged and over discharged protections have successfully been demonstrated for the battery cells. The charging process is disabled when the voltage of the corresponding battery cell exceeds its high limit (HLIM) at 3.65V, and the battery will be available for charging when all of the cell voltages are below their boundary limits (CAVL) at 3.3V. The discharging process will be disabled when the battery cell voltage is lower than the corresponding low limit (LLIM) at 2.5 V. The battery will be available again when all battery cell voltages are above their discharge available (DAVL) voltage at 2.8V. The proposed BMS cell monitoring and protection has shown its function as a data acquisition system, safety protection, ability to determine and predict the state of charge of the battery, and ability to control the battery charging and discharging. Keywords— Battery Management System (BMS), Cell Monitoring, Cell Protection, SOC Estimation, Coulomb Counting I. INTRODUCTION Battery has an important role as energy storage in electricity system utilization, such as portable electronic devices, electric vehicle, and in renewable energy power plant such as in smart microgrid system. Battery with good performance would provide optimal support for the operation of the corresponding system. Battery useful life will be longer if the battery operation is maintained in safety operating area (SOA), either when the battery is charged or discharged. Improper charging and discharging processes could decrease the performance and shorten the battery useful life. Battery Management System (BMS) is needed to treat the dynamics of energy storage process in the battery in order to improve the performance and extend the life of battery. BMS has two operational aspects: monitoring and control. Monitoring aspect cannot be separated from the control aspect. To run proper control of battery charging and discharging processes, a fast, precise and accurate monitoring system is required [1]. An ideal BMS will be energy efficient with low power consumption in achieving the full capacity of battery. The BMS ensures that the battery will not damage due to overcharging, over discharging or over load power consumption [2]. The BMS will examine the operational parameters of the battery e.g. voltage, current, the internal temperature during charging and discharging and estimate the battery state e.g. state of charge (SOC) and state of health (SOH). A BMS which flexible enough to protect different types of batteries and can provide all the safety features, has been a recent topic of development and research in electric vehicle and alternative energy systems [3]. As described in [2], a comprehensive BMS should include functions for data acquisition, safety protection, ability to determine and predict the state of the battery, ability to control battery charging and discharging, cell balancing, thermal management, delivery of battery status and the authentication to a user interface, communication with all BMS components and the most important thing is to prolong battery life. The model of battery is needed to relate the input current rate and its SOC estimation, whereby the coulomb counting methods can be ideal for this purpose. One of SOC estimation algorithm which is based on coulomb counting and taking into account the coulomb efficiency for monitoring system in discrete time, can be expressed as in Equation (1) [4] [5]. 2014 IEEE International Conference on Electrical Engineering and Computer Science 24-25 November 2014, Bali, Indonesia 203