Battery Life Evaluation Using SOC-Dependent Current Profiles
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Solution Overview
Problem
Conventional accelerated life evaluation methods for secondary batteries often cause abnormal deterioration, leading to unreliable cycle life assessments, especially when acceleration conditions exceed normal deterioration limits.
Innovation Solution
A method and apparatus for evaluating secondary battery life by maintaining charging and discharging currents within a normal deterioration range, where the current is reduced as the state of charge increases and decreases, respectively, to prevent abnormal reactions, with the process repeated until a reference state of health is reached, using a control circuit and processor to manage the charging and discharging processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional accelerated life evaluation methods increase environmental temperature or charging/discharging current to speed up evaluation, then the evaluation period is shortened, but abnormal battery deterioration occurs and reliability of evaluation is lowered
Solution Approach 1:
The patent applies dynamics by making the charging/discharging current variable rather than constant. The current is dynamically adjusted based on the state of charge (SOC) level, with higher currents applied at lower SOC and progressively reduced currents as SOC increases. This dynamic current profile allows accelerated testing while staying within the normal deterioration range, thus improving evaluation speed without sacrificing reliability
Solution Approach 2:
The patent changes the parameter of charging/discharging current from a fixed high value to a variable value that depends on SOC. By establishing a current-SOC relationship where current decreases as SOC increases, the method transforms the test conditions to achieve both acceleration and reliability. The environmental temperature is also optimized within a specific range (20-40°C) to support accelerated testing without causing abnormal deterioration
2Loss of time
If high charging/discharging current is applied to accelerate life evaluation, then the evaluation period is reduced, but side reactions are generated and abnormal deterioration occurs
Solution Approach 1:
The patent uses dynamic current adjustment based on SOC to prevent side reactions. By reducing current as SOC increases, the method avoids the high-current conditions that trigger harmful side reactions like electrolyte decomposition and electrode material degradation, while still achieving accelerated evaluation through optimized current profiles and temperature control
Solution Approach 2:
The patent changes the current parameter from constant high current to variable current dependent on SOC. This parameter transformation ensures that current remains below the threshold that generates side reactions at high SOC levels, eliminating harmful effects while maintaining evaluation acceleration through coordinated temperature and current optimization
3Productivity
If accelerated life evaluation exceeds normal deterioration conditions, then evaluation is completed faster, but the reliability of life assessment is compromised
Solution Approach 1:
The patent applies dynamics by implementing a SOC-dependent current profile that adapts test conditions throughout the charging/discharging cycle. This dynamic approach allows the system to operate at higher currents during low-SOC phases (where side reactions are minimal) and reduce currents during high-SOC phases, achieving accelerated evaluation that accurately reflects normal deterioration patterns and maintains life assessment precision
Solution Approach 2:
The patent transforms the test parameter from fixed high current to variable current based on SOC relationships. This parameter change enables the evaluation to proceed faster while staying within normal deterioration boundaries, ensuring that the accelerated test results accurately predict real-world battery life and maintain measurement precision
Data Source
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AI summary
The present disclosure relates to an apparatus and method for secondary battery life evaluation. A state of charge, SOC, and a normal deterioration area for charge/discharge current of a secondary battery are established, the secondary battery is charged within the normal deterioration area of the secondary battery, an accelerated charging current is reduced as the SOC increases, the secondary battery is discharged within the normal deterioration area of the secondary battery, and an accelerated discharging current is reduced as the SOC decreases. Steps are repeated until a state of health, SOH, of the secondary battery reaches a reference SOH. By evaluating the accelerated life of the secondary battery within a normal deterioration range, the second battery life evaluation is highly reliable.