Battery SOC Control Using Corrected OCV Characteristics
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Solution Overview
Problem
Existing methods for calculating the state of charge (SOC) of secondary batteries are inaccurate due to individual variations and degradation, leading to operational precision issues, particularly in hybrid vehicles with narrow operational ranges.
Innovation Solution
A battery control device that uses a state of charge correction mechanism involving a pattern calling unit, correction limit width designation, and direct detection correction to accurately update the SOC-OCV characteristic based on use history and current/voltage values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single SOC-OCV characteristic is used for all batteries, then the device complexity is reduced, but the measurement precision of SOC deteriorates due to degradation and individual variations
Solution Approach 1:
The patent segments the single SOC-OCV characteristic into multiple characteristics stored in a library, each representing different battery conditions (degradation levels, individual variations). The controller selects the appropriate characteristic from the library based on battery identification information, thereby resolving the contradiction between device complexity and measurement precision by organizing characteristics in a structured, selectable manner rather than using a single universal curve.
Solution Approach 2:
The patent changes the parameter of SOC-OCV characteristics by storing multiple variations that account for degradation and individual differences. Instead of using a fixed characteristic, the system provides a selection mechanism that adapts the characteristic parameters to match the specific battery's actual state, thus improving SOC accuracy without significantly increasing operational complexity.
2Measurement precision
If multiple SOC-OCV characteristics are stored to account for degradation and individual variations, then the measurement precision of SOC is improved, but the device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-storing multiple SOC-OCV characteristics in a library before actual battery operation. Each characteristic is prepared in advance to account for specific degradation levels or individual variations. During operation, the controller only needs to identify the battery and select the corresponding pre-prepared characteristic, avoiding the complexity of real-time characteristic generation or adjustment.
3Measurement precision
If the SOC-OCV characteristic is corrected based on direct detection, then the measurement precision is improved, but the reliability deteriorates when correction limit width is not properly controlled
Solution Approach 1:
The patent applies dynamics by making the correction limit width adjustable rather than fixed. The correction limit width can be dynamically changed based on battery identification information and the specific correction scenario. This allows the system to adapt the correction aggressiveness to match the battery's actual condition, improving both accuracy and reliability by preventing over-correction in sensitive scenarios while enabling sufficient correction in cases with larger deviations.
Data Source
AI summary
A battery control device which obtains a state of charge of a secondary battery from characteristics representing a relationship of a state of charge and a voltage of the secondary battery comprises a calling unit which calls a first characteristic among a plurality of the characteristics stored in advance based on use history information of the secondary battery, a correction limit width designation unit which designates a correction limit width for prescribing a tolerance level of correcting the first characteristic, and a direct detection correction unit which creates a second characteristic in which the first characteristic has been corrected according to the correction limit width based on a current value and a voltage value of the secondary battery, wherein the state of charge of the secondary battery is obtained using the second characteristic.