Mathematical models for the discharging behaviors of Lithium iron phosphate battery in various conditions

Lithium iron phosphate battery LiFePO4 is the three-dimensional structure of secondary battery, and widely used in electric buses, electric cars, hybrid cars, electric bicycles, energy storage devices and solar electric motorcycle battery. As environmental consciousness, thr LiFePO4 lithium iron phosphate battery-related industry is booming developed. In order to research the battery discharge characteristics and aging effects on the battery, this thesis set 20A discharge current to obtain lithium iron phosphate battery discharge curve. The discharge curve is obtained by constant current when LABVIEW on record its voltage discharge in time.
In order to analyze the impact of aging on battery performance battery discharge, lithium iron phosphate battery discharge curve records become exceptionally important. Because the open-circuit voltage and internal resistance of lithium iron phosphate has a non-linear changes in different battery capacity. To capture this nonlinear relationship between segments, this paper uses mathematical models to fit two lithium iron phosphate battery discharge voltage to draw mathematical model coefficients, this two mathematical models are all based on the equivalent circuit models. One for a single exponential and polynomial mathematical model and the other is a double exponential mathematical model, the coefficients of these mathematical models can be used as a parameter value to describe the characteristics of the battery discharge curve, by fitting different conditions.