A kind of detection method of lithium battery soh

Abstract

The invention discloses a detection method of a lithium battery SOH (status of health). The detection method comprises the following steps: 1) establishing an equivalent circuit model of a lithium battery, wherein the equivalent circuit model comprises a branch composed of an open-circuit voltage Uoc, a polarized capacitor Cp, an Ohmic internal resistor Ro in serial connection in order; two ends of the open-circuit Uoc are connected with self-discharging resistors Rd in parallel, two ends of the polarized capacitator are connected with polarized internal resistors Rp in parallel, thereby obtaining an equation of the equivalent circuit model of the lithium battery; 2) establishing a discrete system state space equation and observation equation of the battery SOC, the Ohmic internal resistorRo and the self-discharging internal resistor Rd according to the equivalent circuit model equation of the lithium battery; performing iteration computation by adopting an extended Kalman filter algorithm to obtain estimation values of the battery SOC, the Ohmic internal resistor Ro and the self-discharging internal resistor Rd; and 3) regarding the estimation values of the battery SOC, the Ohmicinternal resistor Ro and the self-discharging internal resistor Rd and the cycle index H of the lithium battery as input variables to input into a neural network model, and estimating to obtain the lithium battery SOH.

Description

technical field [0001] The invention relates to the technical field of lithium battery detection, in particular to a detection method for lithium battery SOH. Background technique [0002] With the development of cities and the improvement of living standards, society's demand for fossil energy continues to increase, and the adverse impact of fossil energy on the environment has become increasingly prominent. In response to the ever-increasing energy crisis and environmental pollution, the research and development and promotion of new energy emerged as the times require; power lithium-ion batteries are one of the new energy sources, as a complex electrochemical system, the state of health (SOH) of lithium-ion batteries will As it is gradually degraded by use, it is very important to accurately grasp the SOH of lithium-ion batteries during the use of lithium-ion batteries. However, in actual use, the parameters that characterize the SOH of lithium batteries are difficult to ...

AI Technical Summary

Problems solved by technology

In the first method, the acquisition of the capacity value needs to charge the lithium battery to a fully charged state with constant current and constant voltage under relatively stable conditions, and then use a constant current method to discharge the lithium battery to the cut-off voltage. After many cycles, it is obtained Multiple sets of measurements, and finally take the average value as the current available capacity of the lithium battery. This method has high requirements for the measurement environment and takes a long time, so it is difficult to achieve in practical applications and is suitable for testing in experiments.

In the second method, the change range of the impedance value before and after the aging of the lithium battery is small. The methods for obtaining the impedance value mainly include pulse method and electrochemical impedance spectroscopy, which are easily affected by the environment and are rarely used in actual use.

[0004] At present, there are still two methods for estimating the SOH of lithium batteries. There are two main methods. One is the SOH method based on voltage measurement and estimation: use the measured voltage value to calculate the change of lithium battery voltage during charging, and then estimate the relative lithium battery SOH. Battery SOH; this method relies too much on the measurement of the voltage value. If the error of the measured value is large, it will lead to errors in the SOH value of the lithium battery, resulting in accumulated errors

The second is to estimate the lithium battery SOH estimation method based on the lithium battery capacity: first determine the initial capacity of the lithium battery, charge the lithium battery to the cut-off state of the lithium battery, calculate the charged capacity according to the charging current time, and calculate the lithium battery. Lithium battery capacity at the cut-off time of the battery, using the ratio of the lithium battery capacity at the cut-off time to the rated capacity, the lithium battery SOH is obtained; this method uses the current to calculate the lithium battery capacity, but there is an error in the current measurement process, and the final cut-off lithium battery capacity exists At the same time, there is also a measurement error when the initial capacity of the lithium battery is determined, which is not conducive to the estimation of the SOH of the lithium battery

[0005] To sum up, the current methods used for SOH detection of lithium batteries have relatively large drawbacks.

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