Battery Cell Balancing With Model-Based SoC Estimation
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Solution Overview
Problem
Existing battery monitoring technologies struggle to accurately rebalance battery cells due to nonlinear relationships between open circuit voltage and state of charge, and hysteresis effects, leading to inefficient battery pack performance and reduced lifetime.
Innovation Solution
The method involves receiving sensor measurements, estimating battery properties, and actively rebalancing battery cells while the battery pack is in operation, using models that account for hysteresis and nonlinear relationships to improve accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional voltage-based monitoring is used to detect charge imbalance, then the monitoring system is simple to implement, but the measurement precision is poor due to nonlinear relationships and hysteresis effects
Solution Approach 1:
The patent transforms the monitoring approach from direct voltage measurement to indirect state estimation by changing the measured parameter from voltage to state of charge, using electrochemical models and hysteresis compensation to achieve accurate SoC detection despite nonlinear relationships
Solution Approach 2:
The patent introduces an intermediary estimation system that uses voltage as input but produces state of charge as output, employing electrochemical models and hysteresis compensation algorithms as mediators between the simple voltage measurement and the accurate state detection
2Productivity
If passive balancing methods are used, then the system complexity is low, but the productivity is reduced due to battery downtime required for balancing
Solution Approach 1:
The patent enables continuous balancing operation by implementing active cell-to-cell balancing that can operate simultaneously with battery charging/discharging, eliminating the need to stop battery operations for balancing and maintaining continuous useful action
Solution Approach 2:
The patent performs preliminary state estimation and imbalance detection during normal operation, preparing the balancing system to act immediately when imbalances are detected, rather than waiting for voltage thresholds to trigger passive balancing
3Reliability
If simplified balancing models are used, then the ease of operation is high, but the reliability of balancing is poor due to inaccurate state estimation
Solution Approach 1:
The patent implements feedback mechanisms where state estimation results are continuously monitored and used to adjust balancing control decisions, creating a closed-loop system that improves reliability through iterative refinement of state estimates and balancing actions
Solution Approach 2:
The patent replaces simple voltage-threshold-based mechanical switching with model-based electronic control, using electrochemical models and state estimation algorithms to substitute for traditional simple switching mechanisms, achieving higher reliability through intelligent control
Data Source
AI summary
A method can include modeling a state of each battery cell within a battery pack and contemporaneously with discharging a first subset of battery cells of the battery pack either providing a differential drain on the first subset of battery cells such that battery cells of the first subset of battery cells are discharged faster than a second subset of battery cells or charging the second subset of battery cells (e.g., using the first subset of battery cells) where battery cells are identified as in the first subset or the second subset based on the states of the battery cells.