State of Charge Determination Using Voltage and Temperature Curves
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Solution Overview
Problem
Existing methods for determining the state of charge and remaining operating time of lithium-thionyl chloride batteries in measuring devices, such as utility meters, are inaccurate and prone to error due to slow discharge characteristics, particularly when using coulomb counting.
Innovation Solution
A method that utilizes current and voltage curves during normal operation, combined with temperature measurements, to determine the state of charge and remaining operating time, employing short measurement intervals and machine learning algorithms to extract characteristic properties for improved accuracy and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coulomb counting is used to determine state of charge, then the method is suitable for rechargeable batteries or standard lithium cells, but it is inaccurate and error-prone for lithium-thionyl chloride batteries with slow discharge characteristics
Solution Approach 1:
The patent changes the measurement parameters from current integration (coulomb counting) to voltage and temperature measurements during normal operation. This parameter change makes the method suitable for lithium-thionyl chloride batteries with slow discharge characteristics, as voltage and temperature exhibit clear dependence on state of charge without requiring current integration over long periods that amplifies errors.
Solution Approach 2:
The patent replaces the electrical measurement approach (coulomb counting requiring current integration) with a thermodynamic approach using voltage and temperature measurements. This substitution eliminates the accumulation of integration errors that plague coulomb counting methods when applied to slow-discharge batteries.
2Reliability
If batteries are oversized to last through the entire operating interval, then battery replacement labor costs increase, but the batteries are suitable for most application situations
Solution Approach 1:
The patent enables the battery system to monitor its own state of charge and predict remaining operating time through voltage and temperature measurements during normal operation. This self-service capability allows for timely battery replacement planning, optimizing the balance between battery capacity sizing and replacement frequency without requiring oversized batteries for all scenarios.
Solution Approach 2:
The patent implements feedback by continuously monitoring voltage and temperature during operation to determine state of charge and predict remaining runtime. This feedback mechanism allows dynamic adjustment of replacement schedules, enabling more accurate battery sizing that matches actual consumption patterns rather than using conservative oversized designs.
3Duration of action of stationary object
If current integration is performed over very long operating intervals, then the method can track battery discharge, but small errors in measured currents lead to significant errors in determined state of charge
Solution Approach 1:
The patent replaces current integration over long intervals with voltage and temperature measurements taken during normal operation. This substitution eliminates the cumulative error problem inherent in integrating small current measurements over extended periods, as voltage and temperature provide direct indicators of state of charge without requiring accumulation of measurement data.
Solution Approach 2:
The patent uses periodic voltage and temperature measurements during normal operation to determine state of charge. Rather than continuous current integration, the method samples voltage and temperature at measurement intervals, providing accurate state of charge determination without the error accumulation that occurs with long-duration current integration.
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
Achieves significantly better accuracy and robustness in determining the state of charge and remaining operating time, allowing for timely unscheduled replacements or operational adjustments, reducing the need for oversized batteries and minimizing labor costs.
Implementation Method 1
a non-rechargeable battery with a long service life (2) integrated with other components of the control unit (7) in a common housing
Implementation Method 2
determine the charge state (1) of an energy storage device (2) of a measuring device (3) or to predict a remaining operating time
Implementation Method 3
The temperature of at least one component of the measuring device, in particular the energy storage device (2), is recorded
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Method for determining a charge state (1) of an energy storage device (2) of a measuring device (3) and/or a probable remaining operating time of the measuring device (3), wherein within a respective determination interval (4) several voltage measurements (19) for the voltage drop across the energy storage device (2) and several current measurements (20) for the current supplied by the energy storage device (2) are recorded, after which the charge state (1) and/or the remaining operating time assigned to the respective determination interval (4) are determined as a function of the several voltage measurements (19) and current measurements (20).