Battery State Detection Using Dynamic Time Constant Adjustment
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Solution Overview
Problem
Existing methods for battery state detection, such as voltage division and coulometric methods, face inaccuracies due to measurement errors at low currents and require complex models for precise state of charge estimation, which complicates power management in portable and outdoor devices.
Innovation Solution
A simple battery model is used to update internal resistance and capacitance based on state of charge, allowing for accurate detection by relating open circuit voltage to historical parameters and compensating for variations in charge and discharge cycles and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage division approach is used to determine state of charge, then device structure remains simple, but measurement precision deteriorates with large charge or discharge current
Solution Approach 1:
The patent dynamically adjusts the time constant based on the magnitude of charge or discharge current. When current is large, a longer time constant is used to allow more complete capacitor discharge; when current is small, a shorter time constant is used. This dynamic adjustment optimizes measurement precision across different operating conditions while maintaining the simplicity of the voltage division approach.
Solution Approach 2:
The patent changes the time constant parameter according to the charge or discharge current magnitude. By selecting different time constants (first time constant for large current, second time constant for small current), the system adapts to different measurement conditions and maintains high precision without increasing structural complexity.
2Measurement precision
If measurement time is extended to allow capacitor discharge, then state of charge precision improves, but response speed deteriorates
Solution Approach 1:
The system dynamically adjusts the measurement time based on the charge or discharge current magnitude. For large currents, a longer measurement time is used to ensure complete capacitor discharge and accurate voltage reading. For small currents, a shorter measurement time suffices. This dynamic time adjustment maintains precision while optimizing response speed for different operating conditions.
Solution Approach 2:
The patent changes the measurement time parameter according to the current magnitude. By using a first measurement time for large currents and a second measurement time for small currents, the system achieves both high precision and fast response when conditions permit, resolving the contradiction between measurement time and response speed.
3Measurement precision
If coulometric method is used for state of charge calculation, then precision improves under high current, but measurement errors accumulate at low currents
Solution Approach 1:
The patent dynamically switches between measurement methods based on the magnitude of charge or discharge current. The voltage division method with adaptive time constant is used for large currents, while the coulometric method is used for small currents. This dynamic method selection ensures high precision and reliability across the full range of operating conditions, avoiding the accumulation of measurement errors at low currents.
Solution Approach 2:
The patent changes the measurement method parameter based on current magnitude. By selecting appropriate measurement methods (voltage division for large current, coulometric for small current), the system maintains both precision and reliability across different operating conditions, resolving the contradiction between high-current precision and low-current reliability.
Data Source
AI summary
A method of detecting a state of charge of a battery, can include: obtaining an open circuit voltage in a present cycle according to an open circuit voltage of a previous cycle, a battery internal resistance of the previous cycle, and a battery capacitance of the previous cycle, where the battery internal resistance and the battery capacitance are updated according to the state of charge of the battery; and determining the state of charge of the battery according to the open circuit voltage in the present cycle.