Short Circuit Detection Device for Secondary Battery
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Solution Overview
Problem
Existing short circuit detection methods for lithium-ion secondary batteries fail to accurately detect internal short circuits during fluctuating discharge conditions, such as in electric vehicles, due to difficulties in estimating changes in internal resistance.
Innovation Solution
A short circuit detection device that uses a voltage sensor to detect voltage and current fluctuations, adjusting the load to distinguish between voltage drops caused by internal resistance increases and internal short circuits, and recognizes an internal short circuit by comparing voltage and current fluctuation frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the open-circuit voltage is calculated based on the closed-circuit voltage by measuring the closed-circuit voltage of the lithium-ion secondary battery, then the theoretical value of capacity change can be obtained, but the open-circuit voltage is not accurately calculated when the lithium-ion secondary battery is used in a system in which a fluctuating discharge occurs
Solution Approach 1:
The invention transitions from a static measurement approach (single closed-circuit voltage measurement) to a dynamic approach by repeatedly measuring closed-circuit voltages at different discharge currents and synthesizing the open-circuit voltage through calculation. This dynamic multi-point measurement method adapts to fluctuating discharge conditions by capturing voltage characteristics across varying current levels, thereby maintaining accuracy regardless of discharge mode variations.
Solution Approach 2:
The invention changes the measurement parameter from a single closed-circuit voltage value to multiple closed-circuit voltage values obtained at different discharge currents. By varying the discharge current parameter and measuring corresponding voltages, the system can accurately determine open-circuit voltage even when operating conditions fluctuate, resolving the contradiction between measurement precision and adaptability to different discharge modes.
2Measurement precision
If a steady discharge is maintained, then changes in the internal resistance of the lithium-ion secondary battery can be accurately estimated, but accurate estimation is difficult in a system in which a fluctuating discharge occurs
Solution Approach 1:
The invention replaces the static steady-discharge assumption with a dynamic measurement process that actively varies discharge current and repeatedly measures voltage responses. This dynamic approach enables internal resistance estimation under fluctuating discharge conditions by capturing the relationship between varying current and corresponding voltage changes, thereby maintaining estimation accuracy without requiring steady discharge operation.
Solution Approach 2:
The invention performs preliminary measurements by repeatedly measuring closed-circuit voltages at different discharge currents before calculating the final open-circuit voltage and internal resistance values. This preliminary data collection at multiple current points establishes a foundation for accurate parameter estimation even when the battery operates under fluctuating discharge conditions during normal use.
3Reliability
If the open-circuit voltage is not accurately calculated, then the internal short circuit cannot be accurately detected
Solution Approach 1:
The invention makes the voltage measurement system multi-functional by using the same voltage sensor and control unit for both measuring closed-circuit voltages at different currents and subsequently calculating open-circuit voltage and internal resistance. This universal approach enables accurate short circuit detection without adding separate dedicated measurement devices, thereby maintaining reliability while controlling system complexity.
Solution Approach 2:
The invention introduces calculated open-circuit voltage as an intermediary parameter that bridges the relationship between measured closed-circuit voltages and internal short circuit detection. By using this calculated intermediary value derived from multiple voltage measurements, the system achieves accurate short circuit detection while utilizing existing measurement components, thus balancing reliability with manageable system complexity.
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 accurate real-time detection of internal short circuits regardless of discharge mode, enhancing safety and practicality of battery-powered systems by differentiating between resistance and short circuit-induced voltage drops.
Implementation Method 1
a voltage sensor that detects a voltage of a secondary battery
Data Source
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AI summary
[Problem] To provide a short circuit detection device that can accurately detect in real time an internal short circuit of a secondary battery during discharge, regardless of the mode of use of the secondary battery. [Solution] A short circuit detection device determines whether a first voltage value Va, obtained by detecting with a voltage sensor a voltage of a secondary battery that is discharging to a load, is below a threshold value Vs, and, if the first voltage value Va is below the threshold value Vs, adjusts the load to reduce the current that flows from the secondary battery to the load; the short circuit detection device then determines whether a second voltage value Vb, obtained by detecting with the voltage sensor the voltage of the secondary battery after the adjustment of the load, is less than the first voltage value Va, and, if the second voltage value Vb is less than the first voltage value Va, recognizes that an internal short circuit of the secondary battery has occurred.