Battery SOC Calculation Device Using Static Impedance Voltage
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Solution Overview
Problem
Conventional battery state-of-charge calculation devices face inaccuracies due to large errors in estimated impedance voltage values, leading to incorrect SOC calculations, especially when temperature and current measurements are low in accuracy.
Innovation Solution
A battery state-of-charge calculation device with a first state-of-charge calculation unit based on voltage data, a second state-of-charge calculation unit based on current data, an impedance voltage calculation unit using effective SOC, temperature, and current data, a static determination unit to identify static impedance voltage, and a decision unit to select accurate SOC based on these calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If SOCI is used as SOC based on integrated current value, then calculation simplicity is maintained, but measurement errors accumulate and SOC accuracy deteriorates
Solution Approach 1:
The patent implements feedback by detecting switchover from charge to discharge and using SOCV to correct SOCI. The system continuously monitors voltage and current, detects charge/discharge transitions, and applies correction when needed, creating a closed-loop control that maintains SOC accuracy without requiring completely complex alternative calculation methods
Solution Approach 2:
The patent changes the calculation parameter from purely current-based (SOCI) to a hybrid approach using voltage-based SOCV during charge/discharge transitions. By switching between different calculation parameters based on operating conditions, the system maintains simplicity while improving accuracy
2Measurement precision
If SOCV is calculated using estimated impedance voltage value, then SOC accuracy can be improved, but error in impedance voltage calculation increases when temperature and current measurements are low in accuracy
Solution Approach 1:
The patent performs preliminary detection of charge/discharge switchover events before calculating SOCV. By identifying the transition point first, the system prepares to apply correction only when necessary, avoiding unnecessary calculations that would amplify measurement errors in temperature and current data
Solution Approach 2:
The patent uses the detected charge/discharge switchover event as an intermediary trigger that activates SOCV calculation only when needed. This intermediary mechanism filters out conditions where impedance voltage calculation would be unreliable, allowing SOCV to serve as a corrective mediator rather than a continuous calculation that would propagate errors
Data Source
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AI summary
Disclosed is a battery state of charge calculation device (100) equipped with an SOCV calculation unit (5) that outputs a first state of charge calculated based on voltage data, an SOCI calculation unit (6) that outputs a second state of charge calculated based on current data, an estimated impedance voltage calculation unit (12) that calculates an impedance voltage value based on the effective state of charge and current data, a static decision unit (7) that determines that the impedance voltage value has remained static for longer than a prescribed time within a range delimited with prescribed threshold values and outputs the decision result, and an SOC determination unit (20) that, based on the decision result, outputs the first state of charge as the effective state of charge when the impedance voltage is static, and otherwise outputs the second state of charge as the effective state of charge.