Battery Full Charge Capacity Estimation with Adaptive SOC Thresholds
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Solution Overview
Problem
Existing battery capacity estimation methods struggle to accurately determine full charge capacity regardless of the degree of change in the charged state, leading to potential deviations in estimation results.
Innovation Solution
A method that involves acquiring and integrating current values and changes in state of charge (SOC) to estimate battery full charge capacity using adaptive thresholds based on the frequency and duration of SOC changes, adjusting the estimation criteria to ensure accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed first threshold is used for SOC change amount, then the estimation method is simple to implement, but the estimation accuracy deteriorates when SOC change is small
Solution Approach 1:
The patent applies the dynamics principle by making the threshold dynamic rather than fixed. The threshold is adjusted based on the absolute value of SOC change amount: when |ΔSOC| ≥ first threshold, the first threshold is used; when |ΔSOC| < first threshold, a second threshold (smaller than the first) is used. This dynamic adjustment allows the system to maintain high estimation accuracy across different SOC change conditions while keeping the implementation relatively simple.
Solution Approach 2:
The patent applies parameter changes by modifying the threshold parameter based on the SOC change condition. The threshold parameter takes different values (first threshold or second threshold) depending on the magnitude of SOC change, allowing the estimation method to adapt to different operating conditions and maintain accuracy without complex implementation.
2Device complexity
If calculation is executed only when SOC change is large, then calculation complexity is reduced, but estimation accuracy deteriorates when SOC change is small
Solution Approach 1:
The patent dynamically adjusts the threshold based on SOC change magnitude, allowing the system to maintain accuracy across different conditions. When SOC change is small, the second threshold enables calculation to proceed; when SOC change is large, the first threshold applies. This dynamic approach balances calculation complexity with estimation accuracy.
Solution Approach 2:
The threshold parameter is changed based on the SOC change condition, allowing the system to adapt its calculation criteria. This parameter change enables the system to maintain estimation accuracy without requiring complex calculation structures, as the threshold adjustment is a simple conditional modification.
3Measurement precision
If a lower threshold is always used, then estimation accuracy for small SOC changes is improved, but the frequency of calculation increases leading to higher processing load
Solution Approach 1:
The patent uses dynamic threshold adjustment to balance accuracy and processing load. The threshold is set to the second threshold (lower) only when SOC change is small, enabling accurate estimation in that specific condition. When SOC change is large, the first threshold (higher) is used, reducing calculation frequency and processing load. This dynamic approach optimizes both accuracy and productivity.
Solution Approach 2:
The threshold parameter is adaptively changed based on SOC change magnitude, allowing the system to use a lower threshold only when necessary for accuracy (small SOC changes) and a higher threshold when processing load reduction is beneficial (large SOC changes). This parameter adaptation resolves the contradiction between accuracy and productivity.
Data Source
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AI summary
In a step of estimating a full charge capacity of a battery 1, SOC1 and SOC2 are acquired based on voltages V1 and V2 when the battery 1 is stable. A change amount ΔSOC is acquired from SOC1 and SOC2. A current integrated value ΣA1 until SOC changes from SOC1 to SOC2 is acquired. When |ΔSOC| is equal to or more than a first threshold, the estimation portion 46 calculates an estimated value Hx from ΣA1 and ΔSOC. When a preset condition is satisfied, the estimation portion 46 makes the first threshold be a second threshold. The second threshold is a lower threshold than the first threshold.