Battery Cell Current Distribution via Ladder Circuit Modeling
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Solution Overview
Problem
Existing battery systems struggle to accurately calculate current distribution in secondary batteries, particularly due to geometric structure and salt concentration unevenness, leading to inefficiencies in charging and discharging processes.
Innovation Solution
A battery system and method that utilize a circuit network model to calculate current distribution by geometrically modeling the battery's interior with resistance and power storage elements, considering both geometric structure and salt concentration distribution, allowing for precise estimation and control of current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional battery system performs external charging without considering current distribution, then charging can be performed simply, but the salt concentration unevenness causes high rate deterioration and reduces input/output performance
Solution Approach 1:
The patent segments the battery system into multiple equivalent circuits, each representing a specific region within the battery. This segmentation allows the system to model and control current distribution in different regions independently, addressing the salt concentration unevenness by treating each segment with appropriate resistance values that reflect local conditions.
Solution Approach 2:
The patent dynamically changes resistance parameters in the equivalent circuit model based on detected battery state (such as state of charge and temperature). By adjusting these parameters in real-time, the system adapts to varying salt concentration distributions and optimizes charging control to prevent high rate deterioration while maintaining performance.
2Quantity of substance
If the battery cell size is increased to achieve larger capacity, then energy storage capacity increases, but geometric structure causes current unevenness that is not adequately addressed by conventional models
Solution Approach 1:
The patent divides the large battery cell into multiple smaller equivalent circuit segments spatially arranged to represent different regions. This segmentation enables the model to capture geometric effects and current distribution patterns in large cells, providing accurate measurement of local current density variations that would be missed by a single lumped model.
Solution Approach 2:
The patent transitions from a one-dimensional or lumped circuit model to a multi-dimensional distributed parameter model. By introducing spatial dimensions into the equivalent circuit representation, the system can accurately model current distribution across the extended geometry of large capacity cells, accounting for variations in current paths and resistance throughout the cell volume.
Data Source
AI summary
A battery system includes a battery pack including a plurality of cells, and an ECU. The ECU calculates a current distribution in each cell using a ladder circuit network model, the ladder circuit network model being obtained by geometrically modeling an interior of the cell using a plurality of resistance elements and a plurality of power storage elements. The ECU calculates the current distribution in the cell by applying, to the ladder circuit network model, a resistance distribution in the cell calculated based on a salt concentration distribution in the cell.