Charge Acceptance Limit Determination for Secondary Battery Degradation
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Solution Overview
Problem
Secondary batteries face a challenge in maintaining accurate charge acceptance limits due to degradation, which affects their charging control range and fuel efficiency, as the charge acceptance limit SOC decreases over time due to sulfation on electrode plates, leading to a narrower controllable range and inefficient charging.
Innovation Solution
A charge acceptance limit determination apparatus and method that uses a voltage measuring unit, current measuring unit, and determining unit to plot points on a current-voltage plane, determining the charge acceptance limit based on distances from a base point, with adjustments for degradation and irregular measurements, allowing for accurate determination even with varying voltage and current values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed charge control range (SOC1 to SOC2) is set in advance, then the control system is simple to implement, but the charge acceptance limit cannot be accurately determined as the battery degrades, leading to incorrect charging control
Solution Approach 1:
The patent implements dynamic adjustment of the charge control range based on the determined charge acceptance limit SOC. Instead of using a fixed predetermined range, the system continuously adapts the upper chargeable limit (SOC1) to match the actual charge acceptance limit SOC, which changes as the battery degrades. This dynamic approach ensures accurate charging control throughout the battery's lifecycle while maintaining a relatively simple overall system structure.
Solution Approach 2:
The patent employs feedback mechanisms by measuring voltage and current, plotting them on a current-voltage plane, and using the position relative to a base point to determine the charge acceptance limit SOC. This feedback loop allows the system to continuously monitor battery state and adjust the charge control range accordingly, improving determination accuracy without requiring overly complex hardware.
2Reliability
If the charge control range is adjusted to accommodate battery degradation, then accurate charging control can be maintained, but the system complexity increases due to need for continuous monitoring and adjustment
Solution Approach 1:
The patent enables the battery management system to automatically determine its own charge acceptance limit by monitoring its voltage and current characteristics and comparing them against a base point on the current-voltage plane. The system self-adjusts the charge control range based on its own degradation state without requiring external intervention or complex additional hardware, thereby improving reliability while keeping the system relatively simple.
3Measurement precision
If voltage and current measurements are taken frequently to track battery state, then accurate charge acceptance limit determination is achieved, but energy consumption and measurement complexity increase
Solution Approach 1:
The patent uses voltage and current measurements taken during normal charging operations to determine the charge acceptance limit, rather than requiring separate dedicated measurement cycles. By utilizing existing measurement data and plotting it on the current-voltage plane, the system achieves accurate battery state determination without excessive additional energy consumption or measurement complexity.
Data Source
AI summary
A charge acceptance limit determination apparatus includes a voltage measuring unit that measures a voltage of a secondary battery, a current measuring unit that measures an electric current flowing through the secondary battery, and a determining unit that determines whether or not the secondary battery has reached a charge acceptance limit in accordance with a position on a current-voltage plane of a voltage value and a current value that are measured by the voltage measuring unit and the current measuring unit.