Lithium-Ion SOC Diagnosis Using Lebesgue Sampling and ECM Updates
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Solution Overview
Problem
Traditional state-of-charge (SOC) estimation and prediction methods for lithium-ion batteries face challenges due to high computation costs in electrochemical models and inaccuracies in equivalent circuit models, and the traditional open circuit voltage (OCV) acquisition method is time-consuming and inefficient.
Innovation Solution
The integration of Lebesgue sampling (LS) with the equivalent circuit model (ECM) for lithium-ion batteries, considering the nonlinearity of terminal voltage, allows for parameter updates and reduces computation costs while enabling accurate SOC diagnostics and prognostics by fitting OCV points after sufficient rest periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrochemical model is used for SOC estimation, then accuracy is improved, but computation cost increases
Solution Approach 1:
The patent segments the SOC estimation process into two distinct phases: an offline training phase where the electrochemical model is used to generate accurate training data, and an online estimation phase where a simplified neural network model performs real-time SOC estimation. This segmentation allows the computationally intensive electrochemical model to be used only when necessary for training, while the lightweight neural network handles continuous online estimation with minimal computation cost.
2Measurement precision
If traditional OCV acquisition method is used, then OCV data is obtained, but time consumption increases
Solution Approach 1:
The patent applies preliminary action by performing extensive OCV measurements and data collection during the offline training phase before the battery is actually deployed for use. During this preliminary stage, the battery is discharged at various rates and allowed to rest to establish accurate OCV-SOC relationships. This pre-acquired knowledge is then stored in the neural network model, eliminating the need for time-consuming OCV measurements during online operation.
3Use of energy by moving object
If ECM with fixed parameters is used, then computation cost is reduced, but simulation accuracy deteriorates
Solution Approach 1:
The patent transforms the static fixed-parameter ECM into a dynamic adaptive model by integrating a neural network that continuously updates the ECM parameters based on real-time terminal voltage measurements. The neural network learns the nonlinear relationships between SOC, SOH, and ECM parameters during offline training, enabling the parameters to adapt dynamically during online operation. This dynamic approach maintains high simulation accuracy while keeping the computational burden manageable through efficient neural network inference.
Data Source
AI summary
Method provides accurate state-of-health (SOH) diagnostics and prognostics during the whole-life-service of a lithium-ion battery by considering the effects of state-of-charge (SOC) and SOH on certain parameters (such as consideration of nonlinearity of the terminal voltage) during the process of SOC diagnostics and prognostics. The method integrates Lebesgue sampling and equivalent circuit model (ECM) analysis, which greatly decreases computation cost and uncertainty accumulation to provide efficient acquisition of open circuit voltage (OCV) determinations for the ECM process. The OCV curve of the battery was obtained during Hybrid Pulse Power Characterization testing by fitting a series of selected OCV points after enough rest of the subject battery. Identified parameters of ECM are updated according to terminal voltage measurement to enable accurate SOC estimation and prediction during the period from full charge to full discharge of the battery. Parameter identification is re-conducted and an initial condition for SOC estimation is updated according to SOH to enable accurate SOC estimation during the whole-life-service of battery.


