Secondary Battery State Judging Device for Capacity Balance Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing secondary battery designs, such as nickel-metal hydride batteries, face challenges in accurately judging changes in capacity balance between the cathode and anode due to aging deterioration, leading to errors in State of Charge (SOC) estimation and inadequate charging/discharging control, as the internal state related to capacity balance can only be known by destroying the battery.
Innovation Solution
A state judging device for secondary batteries that measures voltage and current, calculates internal resistance, and judges capacity balance changes based on SOC dependency of internal resistance or no-load voltage, allowing for non-destructive assessment of capacity balance degradation and adaptive control of charging/discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the capacity of the anode is set to be greater than the capacity of the cathode by a predetermined margin, then the battery size, weight, and cost are reduced while avoiding internal pressure increase, but the capacity balance between cathode and anode changes due to aging deterioration leading to SOC estimation errors
Solution Approach 1:
The patent applies preliminary action by pre-storing the initial internal resistance values at multiple SOC points (first through fifth SOCs) when the battery is new. This preliminary data collection enables later comparison with current internal resistance values to detect capacity balance changes due to aging, without requiring destructive testing or complex external measurement equipment.
Solution Approach 2:
The patent implements feedback by continuously monitoring the internal resistance at current SOC and comparing it with the stored initial internal resistance values. When a deviation exceeding a predetermined threshold is detected, the system identifies capacity balance degradation and adjusts the SOC estimation accordingly, creating a closed-loop feedback mechanism that maintains accuracy despite aging.
2Measurement precision
If the capacity balance between cathode and anode is monitored by destructing the battery and inspecting with single electrode capacity measurement, then accurate capacity balance information is obtained, but the battery is destroyed and cannot be used for continued operation
Solution Approach 1:
The patent applies self-service by utilizing the battery's own internal resistance characteristics as the measurement probe. The battery monitors its own capacity balance status through internal resistance measurements at different SOC levels, eliminating the need for external destructive testing equipment while providing accurate diagnostic information that enables continued operation.
Solution Approach 2:
The patent replaces the mechanical destructive disassembly and physical electrode inspection method with an electrical measurement approach. By substituting physical destruction with electrical resistance measurements, the system achieves equivalent diagnostic capability while preserving battery integrity and enabling continued use.
3Productivity
If the SOC-voltage curve is used for SOC estimation, then the SOC can be estimated based on voltage measurement, but when capacity balance changes due to aging, the SOC-voltage curve changes causing estimation errors
Solution Approach 1:
The patent applies parameter changes by shifting from relying solely on the SOC-voltage relationship to using SOC-dependent internal resistance characteristics for detection. When capacity balance changes are detected through internal resistance variations, the system adjusts the SOC estimation by referencing the detected change amount, thereby compensating for aging-induced curve shifts and maintaining accuracy.
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
Enables the detection of capacity balance changes without destroying the battery, facilitating the judgment of degradation and precise control of charging/discharging, thereby extending the battery's usage period and maintaining control accuracy.
Implementation Method 1
a unit which calculates an internal resistance of the secondary battery based on the voltage and the current
Data Source
AI summary
A device which judges a change of a capacity balance between a cathode and an anode of a secondary battery in a non-destructive manner is provided. The secondary battery has one of the capacities of the cathode and the anode greater than the other capacity. A battery ECU calculates an internal resistance (DCIR) of the secondary battery based on a current and a voltage of the secondary battery. When the calculated internal resistance (DCIR) is higher than the initial state in a low SOC region or a high SOC region, the battery ECU judges that the capacity balance between the cathode and the anode of the secondary battery has changed.