State-of-Charge Estimating Device for Vehicle Battery
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Solution Overview
Problem
Existing methods for detecting the upper limit of a secondary battery's state of charge in vehicles are not accurate due to variations during vehicle operation, leading to inaccurate estimation of the full-charge capacity and reduced travel distance.
Innovation Solution
A state-of-charge estimating device and method that integrates charging current from the start to completion of external charging, using different weights for calculating the upper limit based on previous cycles to account for chronological changes, ensuring high accuracy by minimizing variations during rest periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the total capacity of the secondary battery is detected based on integrated current value and charge level difference during vehicle operation, then the detection method is simple, but the measurement precision is low due to large variations in state of charge
Solution Approach 1:
The patent applies preliminary action by performing external charging of the storage device before conducting capacity detection. This preliminary charging action ensures the storage device is in a known initial state (fully charged), which eliminates the problem of large state of charge variations during detection. The detection is then performed during this controlled external charging period rather than during normal vehicle operation, thereby achieving high measurement precision while maintaining method simplicity.
2Productivity
If the state of charge varies during vehicle running, then the storage device can be used for power supply, but the detection accuracy of full-charge capacity reduction deteriorates
Solution Approach 1:
The patent extracts the capacity detection function from the normal vehicle operation context and performs it separately during external charging. By taking out the detection process from the dynamic vehicle operation environment, the system eliminates the interference of state of charge variations caused by vehicle power supply activities. This allows the vehicle to maintain its power supply function during normal operation while achieving accurate capacity detection during dedicated external charging periods.
3Measurement precision
If external charging is used to detect total capacity, then the integrated current value can be calculated accurately, but the device complexity increases due to additional charging infrastructure
Solution Approach 1:
The patent applies self-service by utilizing the external charging infrastructure that is already necessary for charging the storage device. The same external charging system that serves the primary function of charging the battery is also used for capacity detection, eliminating the need for separate detection equipment. This approach maintains high measurement precision through accurate integrated current calculation while avoiding additional device complexity, as the charging infrastructure serves dual purposes.
Data Source
AI summary
A PM-ECU executes a program including: a step (S104) of estimating pre-charge SOC(1) when a plug-in charge is started (YES in S100), a step (S108) of calculating an integrated value of charging current when integration permitting conditions are satisfied (YES in S104, YES in S106), a step (S112) of setting a final integrated value when the charge is completed, a step (S116) of estimating post-charge SOC(2) when an ignition switch is turned on (YES in S114), a step (S122) of calculating a full-charge capacity of this cycle when calculation conditions are satisfied (YES in S120), a step (S128) of calculating a new full-charge capacity when the full-charge capacity of this cycle is within a specified range (YES in S124), and a step (S130) of updating the full-charge capacity by setting the new full-charge capacity as the current full-charge capacity when the new full-charge capacity is within a specified range (YES in S128).