Battery State of Charge Calculation Using Current Rate
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Solution Overview
Problem
Existing methods for determining the state of charge (SOC) of a battery during the charging phase are inaccurate, especially when the battery voltage is constant, leading to premature battery removal or overcharging, as they lack a reliable means to correct SOC errors without a coulomb counter.
Innovation Solution
A system with a current sensor and processor calculates the rate of change of the battery's state of charge based on the charge current, allowing for an updated SOC calculation during charging, preventing SOC from reaching 100% prematurely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional SOC determination methods (OCBV lookup table or crude counter) are used during charging, then device complexity is reduced, but measurement precision of SOC deteriorates when battery voltage is constant
Solution Approach 1:
The patent implements feedback by continuously monitoring charging current and using it to calculate the rate of change of SOC. The system adjusts SOC estimates based on actual current measurements, creating a closed-loop system that corrects errors in real-time. This feedback mechanism enables accurate SOC determination during constant voltage charging without requiring complex hardware modifications.
Solution Approach 2:
The patent changes the approach from using voltage-based parameters (OCBV lookup tables) to current-based parameters for SOC calculation. By monitoring charging current and calculating its integral over time, the system adapts to the constant voltage charging condition where traditional voltage-based methods fail. This parameter change enables accurate SOC tracking throughout the entire charging process.
2Measurement precision
If coulomb counter is used to accurately track SOC during charging, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing current sensor serve multiple functions: it not only monitors charging current for power management but also provides the data needed for accurate SOC calculation. By utilizing the current sensor's measurements for dual purposes, the system achieves coulomb counting accuracy without adding dedicated hardware, thus reducing overall device complexity while maintaining high measurement precision.
Solution Approach 2:
The system uses its own existing current measurement capabilities to solve the SOC tracking problem during charging. Rather than relying on external complex hardware, the patent enables the charging system to self-determine SOC accuracy by integrating current measurements and calculating rate of change, making the system self-sufficient and avoiding additional complexity.
3Productivity
If SOC calculation does not account for charging phase characteristics, then calculation speed is maintained, but reliability of SOC information deteriorates leading to premature battery removal or overcharging
Solution Approach 1:
The patent implements dynamic SOC calculation that adapts to different charging phases. The system detects whether the battery is in constant current or constant voltage phase and adjusts the calculation methodology accordingly. During constant voltage phase, it uses current-based rate of change calculation, while during constant current phase, it can use simpler methods. This dynamic adaptation maintains calculation speed while ensuring reliability across all charging conditions.
Data Source
AI summary
Described is a system and method for determining determining a present state of charge of a battery and determining a rate of change of the state of charge of the battery, the rate of change being determined based on a charge current being supplied to the battery. Then, an updated state of charge is determined based on the rate of change.