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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.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.

Batteries have an important role in the development of electrical energy utilization, such as in renewable energy and electric vehicles. Batteries with good performance would support the devices which utilized them. Because the amount of energy stored in a battery is limited, so battery getting charging and discharging cycles. Improper charge and discharge process could decrease the battery's performance. Therefore battery management system (BMS) is very necessary so that could maintain performance of the battery at optimum condition. One of the important aspect in BMS is state of charge (SoC), which indicate the amount of energy left in the battery. In this work, SOC estimation calculated using Coulomb Counting method which is calculate and compare the electric charge that came in and came out the battery. Upon Coulomb counting on discharging and charging process, battery's SoC estimated by different ways, namely calculate the Peukert's effect and calculate charging efficiency, respectively. Modified Peukert relationship includes current rate parameters are affecting discharge capacity of a battery. Higher Peukert constant would lead to decreasing of operational battery module voltages. Moreover, it could be studied that Peukert only has an effect in the changes of discharge capacity at zero point of SoC. Furthermore, from experimental result it has been known that energy stored in the battery might be has different deep of discharge depends on Peukert constant.

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