Abstract: Lithium iron phosphate batteries account for a large proportion of the total investment in grid side energy storage, power side energy storage, and user side energy storage. Reasonable selection of battery capacity is crucial for the construction of energy storage power stations. This article analyzes the typical application scenarios of three types of energy storage, calculates the energy storage time requirements in different scenarios, and combines my engineering practice to provide the conventional configuration and configuration principles for the charging and discharging time of the three types of energy storage. After determining the charging and discharging time of the grid connection point, taking into account the efficiency of each link in the energy storage system, battery attenuation, charging and discharging depth, and other parameters, a calculation method for the minimum rated capacity of the battery that meets operational requirements is derived.