Method and system for estimating open circuit voltage of Li-ion batteries with temperature input

A method for estimating open circuit voltage of lithium ion battery with temperature input, characterized in that, it comprises the following steps:

• step 1:
• deriving an undetermined equation for estimating the open circuit voltage with temperature input according to a gas-liquid dynamic model, and embedding the undetermined equation for estimating the open circuit voltage with temperature input into a single chip microcomputer of an open circuit voltage estimation module,
• wherein, according to an ideal gas state equation, a gas dissolution equilibrium equation and a Bernoulli equation, the undetermined equation for estimating the open circuit voltage is derived as follows:
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• 3
• =
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• P
• 2
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• wherein
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• P0, I and P1 represent an orifice pressure, a gas flow rate and a pressure inside a container under steady state in the gas-liquid dynamic model, respectively, and correspond to a terminal voltage, a current and the open circuit voltage in the battery respectively;
• P3 represents a gas pressure in the container under steady state to be estimated in the gas-liquid dynamic model, and represents the open circuit voltage to be estimated in the battery,
• P2 is a gas pressure in the container during exhausting or inflating process
• T1 represents a steady-state gas temperature in the container at a previous moment in the gas-liquid dynamic model, and represents a steady-state battery temperature at the previous moment in the battery,
• T2 represents a temperature of the gas in the container during the exhausting or inflating process in the gas-liquid dynamic model, and represents a battery temperature during a discharging or charging process in the battery,
• ρ represents a density of gas flow,
• μ represents a resistance coefficient of gas flow,
• k1 represents a first equivalent parameter, and
• k2 represents a second equivalent parameter;
• step 2:
• identifying and estimating equation parameters according to an experimental test, wherein,
• open circuit voltages corresponding to different currents, terminal voltages and temperatures are obtained through the experimental test, optimal values of the parameters k1, k2, ρ and μ in the undetermined equation for estimating the open circuit voltage are identified by identification methods, and
• then the optimal values of the parameters k1, k2, ρ and μ are assigned to the undetermined equation for estimating the open circuit voltage in the step 1 to obtain a complete equation for estimating the open circuit voltage;
• step 3:
• acquiring a current signal of the battery with a current sensor in a signal acquisition module,
• acquiring a temperature signal of the battery with a temperature sensor in the signal acquisition module,
• acquiring a voltage signal of the battery with a voltage sensor in the signal acquisition module,
• transmitting the acquired current signal, temperature signal, and voltage signal to the single chip microcomputer, and
• designing a method for estimating the open circuit voltage with temperature input according to the complete equation for estimating the open circuit voltage;
• and calculating to obtain an estimated value of the open circuit voltage.