Battery Capacity Estimation Using OCV Correction Without Interruptions
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Solution Overview
Problem
Existing methods for estimating the full charge capacity of secondary batteries require multiple interruptions during charging and discharging, increasing the time required for these processes and potentially leading to inaccuracies due to polarization effects.
Innovation Solution
An estimation system that calculates a first charging rate using current integration and a previously estimated full charge capacity, followed by a second charging rate after a predetermined time has elapsed, allowing for correction of the full charge capacity based on the difference between the two rates to account for polarization effects, thereby eliminating the need for interruptions during charging or discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple interruptions are introduced during charging and discharging to eliminate polarization effects, then measurement precision of full charge capacity is improved, but loss of time increases due to repeated stopping and restarting
Solution Approach 1:
The system performs preliminary action by storing voltage values at specific SOC points (10%, 30%, 50%, 70%, 90%) during charging and discharging processes before polarization significantly affects measurements. By pre-capturing these voltage values at predetermined intervals, the system eliminates the need for repeated interruptions to wait for polarization convergence, thereby maintaining measurement precision while reducing time loss.
Solution Approach 2:
The system implements feedback by continuously monitoring the relationship between SOC and voltage, and using the stored voltage values to calculate and update the open circuit voltage-SOC characteristic values. This feedback mechanism allows the system to dynamically adjust and refine full charge capacity estimates without requiring multiple stopping and restarting cycles, thus improving measurement accuracy while minimizing time loss.
2Productivity
If charging and discharging are continuously performed without interruptions, then productivity is improved, but measurement precision deteriorates due to polarization effects
Solution Approach 1:
The system performs preliminary action by capturing voltage values at predetermined SOC intervals during continuous charging and discharging operations. By pre-storing these voltage measurements before polarization effects become significant, the system maintains continuous operation (high productivity) while ensuring accurate voltage data is captured for later calculation of full charge capacity (maintaining measurement precision).
Solution Approach 2:
The system replaces the mechanical approach of repeatedly stopping and restarting charging/discharging operations with an electronic/computational approach. Instead of physically interrupting the process to wait for polarization convergence, the system uses voltage-SOC relationships and calculations to determine full charge capacity, thereby maintaining continuous operation while achieving accurate measurements.
3Measurement precision
If the charging process is stopped and restarted multiple times to acquire voltage values, then measurement precision is improved, but device complexity increases due to additional control operations
Solution Approach 1:
The system performs preliminary action by establishing predetermined SOC intervals (10%, 30%, 50%, 70%, 90%) and pre-planning to capture voltage values at these specific points during charging and discharging. This predetermined framework simplifies the control logic compared to complex real-time detection of polarization convergence, as the system only needs to monitor when SOC reaches these predetermined levels and capture corresponding voltage values.
Solution Approach 2:
The system uses parameter changes by transitioning from continuous monitoring approaches to discrete sampling at predetermined SOC intervals. By changing the measurement parameter from continuous voltage monitoring to sampled voltage capture at specific SOC points, the system reduces control complexity while maintaining measurement precision through strategic sampling at key states.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate estimation of the full charge capacity without increasing the time required for charging or discharging, ensuring the full charge capacity is close to its true value without the need for multiple interruptions.
Implementation Method 1
a secondary battery configured to be charged using electric power supplied from an external power source
Implementation Method 2
a monitoring device configured to detect a voltage and a current of the secondary battery
Implementation Method 3
calculate a second charging rate of the secondary battery using an open circuit voltage of the secondary battery, when a predetermined time has elapsed without charging and discharging since the first charging rate is calculated
Data Source
AI summary
An estimation system, includes: a secondary battery; a monitoring device that detects a voltage and a current of the secondary battery; and a processor that estimates a full charge capacity of the secondary battery using a detection result of the monitoring device. The processor calculates a first charging rate of the secondary battery using a current integration amount in charging, discharging, or charging and discharging of the secondary battery and using a full charge capacity of the secondary battery that was estimated last time; calculates a second charging rate of the secondary battery using an open circuit voltage of the secondary battery, when a predetermined time has elapsed without charging and discharging since the first charging rate is calculated; and performs correction, when a magnitude of a difference between the first and second charging rates is larger than a threshold, on the full charge capacity based on the difference.