Vehicle Battery SOC Adjustment for High-Rate Deterioration
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Solution Overview
Problem
Existing battery systems for vehicles face high-rate deterioration due to salt concentration unevenness, which increases internal resistance and decreases input-output performance, particularly during over-discharge and over-charge conditions, and existing external charging methods may further exacerbate this issue.
Innovation Solution
A battery system with an electronic control unit that adjusts the State of Charge of the secondary battery within a predetermined range, applies specific over-discharge and over-charge currents to identify and moderate high-rate deterioration, and then executes external charging to restrain the progression of high-rate deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external charging is executed to moderate high-rate deterioration, then battery performance is improved, but salt concentration unevenness may further progress under certain conditions
Solution Approach 1:
The system executes a state of charge adjustment process before external charging to bring the SOC within a predetermined range (40%-70%) where negative electrode expansion-contraction is minimal. This preliminary action prevents electrolyte push-out and ensures that subsequent external charging will moderate high-rate deterioration rather than exacerbate salt concentration unevenness
Solution Approach 2:
The system monitors the state of charge and executes different processes (first, second, or third process) based on feedback from the state of charge level. This feedback mechanism ensures that external charging is only executed when conditions are favorable for moderating high-rate deterioration without worsening salt concentration unevenness
2Reliability
If State of Charge is adjusted within a narrow predetermined range, then high-rate deterioration is moderated, but charge-discharge flexibility is reduced
Solution Approach 1:
The system performs state of charge adjustment as a preliminary step before external charging, temporarily constraining SOC to the 40%-70% range only when high-rate deterioration is detected. This allows the system to maintain broader charge-discharge flexibility during normal operation while ensuring optimal conditions for deterioration moderation when needed
Solution Approach 2:
The system dynamically adjusts the state of charge range based on the detected level of high-rate deterioration. During normal operation, the battery can operate across its full SOC range for maximum flexibility. When high-rate deterioration is detected, the system transitions to a controlled SOC range (40%-70%) to moderate deterioration, then returns to normal operation after external charging completes
Data Source
AI summary
In a case where high-rate deterioration of a secondary battery progresses before execution of external charging by a charging device, an electronic control unit (ECU) executes an SOC adjustment process of adjusting an SOC of the secondary battery such that the SOC falls within a predetermined range. The predetermined range is a range where an expansion-contraction change of a negative electrode of the secondary battery along with charge and discharge of the secondary battery is small as compared with a case where the SOC is out of the predetermined range. After the execution of the SOC adjustment process, the ECU executes a process of moderating the high-rate deterioration so as to moderate the high-rate deterioration, and then executes the external charging.