Sub-Battery Capacity Estimation Using OCV Drop Timing
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Solution Overview
Problem
Existing methods for estimating the full charge capacity of redundant system batteries, such as sub-batteries, are inadequate as they temporarily lower the state of charge, making them unsuitable for backup when the main battery fails.
Innovation Solution
A method that estimates the full charge capacity of redundant system batteries by measuring the time it takes for the battery voltage to drop after polarization resolution, then calculates the state of charge using pre- or post-deterioration SOC-OCV characteristic curves based on the measured time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current integration method is used to estimate full charge capacity, then measurement precision is improved, but the state of charge temporarily decreases during discharging processing
Solution Approach 1:
The patent applies preliminary action by measuring the open circuit voltage at a specific timing (after polarization resolution) before the actual capacity estimation calculation. This allows the system to determine the state of charge and full charge capacity without requiring the battery to be discharged to low SOC, thus maintaining backup reliability while achieving measurement precision.
Solution Approach 2:
The patent uses the open circuit voltage as an intermediary parameter to indirectly determine the state of charge and full charge capacity. Instead of directly measuring capacity through discharge (which lowers SOC), the system measures voltage at a specific timing and uses the SOC-OCV characteristic curve to calculate the capacity, thus avoiding the harmful effect of SOC reduction while maintaining measurement accuracy.
2Measurement precision
If discharging processing is performed to estimate full charge capacity, then measurement precision is improved, but the state of charge of the sub-battery decreases
Solution Approach 1:
The patent performs the voltage measurement at a predetermined timing after polarization resolution, before any discharge estimation is needed. This preliminary measurement allows the system to calculate the full charge capacity without actually discharging the battery, thus preserving the state of charge while achieving accurate measurement.
Solution Approach 2:
The patent replaces the physical discharge process (mechanical/electrical energy consumption) with an electrical measurement and calculation approach. Instead of physically discharging the battery to measure capacity, the system measures the open circuit voltage and uses mathematical models (SOC-OCV characteristic curve) to calculate the capacity, substituting physical energy consumption with electrical measurement and computation.
3Reliability
If the sub-battery maintains high state of charge for backup, then reliability is improved, but the ability to perform accurate full charge capacity estimation is reduced
Solution Approach 1:
The patent introduces the open circuit voltage as an intermediary measurement that can be taken at any state of charge. By measuring the voltage at a specific timing (after polarization resolution) and using the SOC-OCV characteristic curve, the system can accurately estimate the full charge capacity regardless of the current state of charge, thus maintaining both backup reliability and measurement precision.
Solution Approach 2:
The patent changes the measurement parameter from direct capacity measurement (which requires discharge) to open circuit voltage measurement at a specific timing. This parameter change allows the system to obtain accurate capacity information without altering the state of charge, thus maintaining backup capability while enabling precise estimation.
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 precise estimation of full charge capacity without lowering the state of charge, ensuring the sub-battery can provide backup power when needed.
Implementation Method 1
a determination unit that determines whether polarization of the battery is resolved after an ignition switch of the vehicle is turned off
Implementation Method 2
measures an amount of time from a time of the determination until the voltage of the battery decreases to a first threshold value due to dark current consumption by the redundant load
Data Source
AI summary
This device estimates the full charge capacity of a redundant system battery that supplies electric power to a redundant vehicle load, and includes an acquisition unit that acquires battery voltage, a determination unit that determines whether the polarization of the battery has been resolved after the ignition switch of the vehicle is turned off, a measurement unit that measures, when it is determined that the polarization has been resolved, the time from the time of determination until the voltage of the battery decreases to a first threshold due to dark current consumption, and a calculation unit that calculates, when the measurement time is greater than or equal to a second threshold, the battery state of charge based on the SOC-OCV characteristic curve before deterioration, and calculates, when the measurement time is less than the second threshold, the battery state of charge based on the SOC-OCV characteristic curve after deterioration.