Battery Pack SOC Control for Capacity-Preserving Storage
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Solution Overview
Problem
The battery capacity of lithium ion secondary batteries degrades due to both the positive and negative electrodes, necessitating a solution to increase battery life by suppressing this degradation.
Innovation Solution
The battery is stored and managed by controlling the state of charge (SOC) to a value lower than the standard SOC, using a system with a battery controller that monitors and adjusts the SOC to prevent capacity degradation, employing specific electrode materials and charge/discharge strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the battery is stored at a high state of charge (SOC) to ensure readiness for use, then the battery availability is improved, but the battery capacity degrades faster and life decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the storage SOC to a specific range (30-70%) rather than storing at high charge levels. This parameter adjustment prevents capacity degradation while ensuring the battery remains ready for use, resolving the contradiction between availability and lifespan
Solution Approach 2:
The patent implements preliminary action by pre-charging the battery to the optimal SOC range before storage or extended periods of non-use. This advance preparation ensures the battery is ready for immediate use while preventing degradation that would occur at higher charge levels during storage
2Quantity of substance
If the battery is fully charged to maximize capacity utilization, then the energy storage is improved, but the degradation of both positive and negative electrodes accelerates
Solution Approach 1:
The patent changes the operating parameters by limiting the charge-discharge SOC range to 30-70% during normal operation and storage. This parameter optimization maintains sufficient energy storage capacity while significantly reducing electrode degradation, preventing capacity loss over time
Solution Approach 2:
The patent applies partial action by intentionally not charging the battery to 100% capacity under normal conditions. By maintaining SOC within the 30-70% range, the system achieves sufficient energy storage for practical use while avoiding the excessive charging that causes accelerated electrode degradation
Data Source
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AI summary
Provided is a secondary battery system capable of suppressing degradation of a battery capacity. When it is determined that a battery pack 41 is brought into a non-use state, a battery state detection unit 523 in a battery controller 52 compares an SOC of the battery pack 41 calculated by a battery state operation unit 522 and a standard SOC (S003). When the SOC of the battery pack 41 is higher than the standard SOC, the battery state detection unit 523 in the battery controller 52 calculates a capacity value in which the SOC of the battery pack 41 becomes lower than the standard SOC, from a difference of the SOC of the battery pack 41 and the standard SOC, and transmits the calculated capacity value to a cell controller 51 (S004). The cell controller 51 discharges the battery pack 41, on the basis of the capacity value transmitted from the battery state detection unit 523 (S005).