Battery Current Control Using Estimated and Measured Values
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Solution Overview
Problem
Existing input/output control devices for secondary batteries in vehicles fail to reliably prevent overheating due to inaccuracies in current sensing, leading to potential overdischarge and increased heat generation in batteries and peripheral components.
Innovation Solution
An input/output control device that estimates battery current based on power input/output and combines this with measured current values, using time-based smoothing of squared values to control power limits, and adjusts these limits based on temperature and differences between estimated and measured values to prevent excessive heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensing means is used to measure battery current, then discharge current can be monitored, but measurement accuracy deteriorates when failure occurs
Solution Approach 1:
The patent introduces an intermediary estimation mechanism that calculates battery current indirectly through power balance equations. When the current sensor fails, the system uses the relationship between voltage, power, and current to estimate the actual current flow, thereby maintaining measurement reliability without depending solely on the physical sensor
Solution Approach 2:
The system continuously compares the sensor-measured current with the estimated current and uses this feedback to detect sensor failures. When a discrepancy exceeds a threshold, the system switches to using the estimated current value, ensuring continuous reliable operation through adaptive feedback control
2Reliability
If current limiting control is implemented based on sensor values, then sudden voltage lowering can be prevented, but overheating occurs when sensor values are incorrect
Solution Approach 1:
The control system continuously monitors both the sensor current and estimated current, comparing them in real-time. When they diverge significantly, the system switches to using the estimated current for control decisions, preventing incorrect current limiting that would cause overheating while maintaining voltage stability through continuous feedback adjustment
Solution Approach 2:
The system dynamically adjusts which current value (sensor-measured or estimated) is used for control based on real-time comparison results. This dynamic switching mechanism ensures that the most accurate current information is always used for voltage and temperature control, preventing both voltage instability and overheating
3Device complexity
If only measured current is used for control, then device complexity is reduced, but protection reliability deteriorates when sensing fails
Solution Approach 1:
The patent introduces an intermediary estimation calculation that uses readily available electrical parameters (voltage, power) to derive current information without requiring additional sensors. This intermediary mechanism adds minimal complexity while significantly improving protection reliability by providing a backup current measurement method
Solution Approach 2:
The system uses its own existing electrical measurements (voltage and power) to self-generate the current estimation without external assistance. This self-service approach minimizes additional device complexity while ensuring reliable battery protection through redundant current information sources
Data Source
AI summary
An input/output control device for a secondary battery mounted on a vehicle includes a current estimating unit estimating a battery current input to or output from the secondary battery based on an input/output power of the secondary battery and outputting an estimated value (estimated current (Is)), a current sensor measuring the battery current and outputting a measured value (measured current (It)), and an input/output control unit controlling the input/output power based on the estimated value and the measured value. The input/output control device controls the input/output of the secondary battery, using the measured current (It) as well as the estimated value (Is), and therefore can suppress more reliably significant increase in heating value of the secondary battery and its peripheral parts.