Battery Management Controller for Continuous SoC Estimation
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Solution Overview
Problem
Conventional battery management systems experience abrupt changes in estimated state of charge (SoC) when transitioning from normal to end-of-discharge or fully-charged states due to independent estimation methods, leading to inaccuracies and potential battery aging issues.
Innovation Solution
A battery management controller that combines coulomb counting with a remaining-capacity lookup table to provide a continuous and accurate estimation of SoC, eliminating abrupt changes by calculating the full available charge capacity and updating it based on aging factors and temperature considerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If independent estimation methods (coulomb counting for normal state, lookup table for end-state) are used for different battery states, then each method can be optimized for its specific state, but the estimated state of charge changes abruptly when transitioning between states
Solution Approach 1:
The patent combines coulomb counting method and lookup table method into a unified estimation framework. The processor uses coulomb counting to track cumulative charge flow and simultaneously references the lookup table for state-dependent corrections. These two previously independent methods are merged to produce a continuous SoC estimate that maintains accuracy across all battery states including transitions.
Solution Approach 2:
The lookup table is pre-computed and stored with capacity values corresponding to different battery states (normal, close-to-end-of-discharge, close-to-fully-charged). This preliminary preparation allows the processor to smoothly transition between estimation approaches by simply switching table references, avoiding abrupt changes in the estimated SoC during state transitions.
2Device complexity
If coulomb counting method is used for normal charging/discharging states, then the method is simple and computationally efficient, but errors accumulate and the estimate becomes inaccurate near end-of-discharge or fully-charged states
Solution Approach 1:
The patent segments the battery operation into distinct states (normal charging/discharging, close-to-end-of-discharge, close-to-fully-charged) and applies different estimation strategies for each segment. Coulomb counting is used for normal states where it remains accurate, while lookup table-based methods are applied for end-states where coulomb counting errors accumulate. This segmentation allows each method to operate in its optimal range.
Solution Approach 2:
The patent changes the estimation parameter approach based on battery state. For normal states, it relies on cumulative charge flow parameters from coulomb counting. For end-states, it transitions to using voltage-current-temperature parameters from the lookup table. This parameter change strategy maintains accuracy while avoiding the computational complexity of continuously using the more accurate but complex method.
3Measurement precision
If lookup table method is used for end-of-discharge or fully-charged states, then the method provides accurate estimates for these specific states, but causes abrupt changes in estimated SoC when transitioning from normal states
Solution Approach 1:
The patent introduces an intermediary approach where the lookup table provides correction factors or reference values that are blended with the coulomb counting results. Rather than directly switching between independent methods, the lookup table acts as a mediator that guides the coulomb counting estimate toward accurate values at end-states, ensuring smooth transitions without abrupt changes.
Data Source
AI summary
In a battery management controller, analog-to-digital conversion circuitry converts analog signals, indicative of a battery voltage, a battery current, and a battery temperature, to digital signals. A memory stores a remaining-capacity lookup table that includes multiple groups of data. Each group of data includes a voltage, a current, a temperature, and a parameter associated with a remaining capacity corresponding to the voltage, the current and the temperature. A processor searches the lookup table for a current parameter value and an end-of-discharge parameter value based on the digital signals, and determines a full available charge capacity of the battery based on the current parameter value and the end-of-discharge parameter value. The processor also counts the number of charges flowing through the battery based on a battery current. The processor further determines an available state of charge of the battery according to the full available charge capacity and the number of charges.