Battery SOC Detection Circuit Using Coulomb Counting and Voltage Correction
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Solution Overview
Problem
The existing battery management systems face issues in accurately detecting the state of charge (SOC) of rechargeable batteries due to voltage drops during discharging, leading to incorrect SOC readings and abrupt changes when switching from discharging to charging, which affects user experience.
Innovation Solution
A method that integrates charge and discharge currents to generate a coulomb count value, corrects the raw SOC value based on voltage drops during discharging, and adjusts the SOC calculation during charging to prevent unnatural jumps by matching the minimum value reached during discharging, ensuring a continuous increase towards 100% SOC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the coulomb calculation method is used to detect SOC during battery operation, then the remaining capacity can be determined during charging or discharging, but the SOC value shows unnatural changes when switching from discharging to charging
Solution Approach 1:
The patent applies preliminary action by detecting and recording the minimum SOC value (SOCmin) reached during the discharging period before charging begins. This pre-detected value is then used as a reference point to adjust the SOC calculation during charging, ensuring that the SOC transitions smoothly from the minimum discharge value rather than showing unnatural jumps. The preliminary detection of SOCmin establishes a baseline that guides subsequent SOC calculations during the charging phase.
2Measurement precision
If the voltage method is used to determine OCV and SOC, then the remaining capacity can be determined according to OCV-SOC correspondence, but OCV cannot be determined when the battery is in no-load and non-relaxed state
Solution Approach 1:
The patent uses the minimum SOC value (SOCmin) detected during discharging as an intermediary reference point to bridge the gap between voltage method and coulomb calculation method. Instead of directly relying on OCV during charging (which may not be accurate), the system uses SOCmin as a mediator to adjust and calibrate the SOC calculation, combining advantages of both methods while avoiding their individual limitations.
Solution Approach 2:
The patent dynamically changes the SOC calculation parameters based on the battery's operational state. During discharging, the system detects SOC using standard coulomb calculation and records the minimum value. During charging, it adjusts the calculation by adding the difference between current SOC and SOCmin to ensure continuity. This parameter adjustment allows accurate SOC detection across different operational phases without requiring OCV measurements in all states.
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
This approach improves the accuracy of SOC detection, preventing abrupt changes and ensuring a consistent user experience by correctly reflecting the battery's state of charge during both discharging and charging cycles.
Implementation Method 1
the remaining capacity is determined by integrating the charging current flowing into the battery and the discharging current flowing out from the battery (hereinafter referred to as charge and discharge current) to calculate the amount of charged electric charges and the amount of discharged electric charges with respect to the battery
Data Source
AI summary
The present invention provides an improved method for detecting the state of charge (SOC) of a battery. A remaining capacity detection circuit detects the SOC of a rechargeable battery. A coulomb counter circuit integrates the charge and discharge currents IBAT of the battery to generate a coulomb count value CC. A voltage detection circuit detects a voltage VBAT of the battery. An SOC calculation unit calculates a raw SOC value SOC_cc based on the coulomb count value CC. A discharge correction unit corrects the raw SOC value SOC_cc based on a voltage drop of the battery during the discharging of the battery, and generates a discharge SOC value SOC_dis. A charge correction unit measures a minimum value SOC_dis_min reached by the discharge SOC value SOC_dis during the last discharge of the battery, and calculates a charge SOC value SOC_chg using the minimum value SOC_dis_min during the charging of the battery.