Extrapolating Battery No-Load Voltage
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Solution Overview
Problem
Existing methods for determining the no-load voltage of electrochemical energy stores, such as lead-acid batteries, are prone to errors due to temperature changes, quiescent current variations, and charge removal during the idle phase, especially in applications like motor vehicles where rest periods are not available.
Innovation Solution
A method that measures the terminal voltage, current, and temperature at predetermined intervals during the rest phase of the electrochemical energy store, using extrapolation to determine the no-load voltage while compensating for temperature, current, and charge effects, normalizing the voltage to a standard temperature and accounting for polarization voltage and charge withdrawals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery is allowed to rest for more than 10 hours to determine open-circuit voltage, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies preliminary action by performing compensation calculations for temperature and polarization voltage effects during the rest period before the full 10 hours elapse. By measuring temperature and current at multiple time points and extrapolating the voltage decay curve with compensation factors, the method obtains accurate open-circuit voltage estimates without requiring the complete 10-hour rest period, thus reducing time loss while maintaining measurement precision.
2Object-affected harmful factors
If temperature compensation is applied after voltage extrapolation, then temperature dependence is compensated, but measurement precision deteriorates due to transient process misinterpretation
Solution Approach 1:
The patent applies preliminary action by performing temperature compensation during the voltage decay extrapolation process itself, rather than after obtaining the extrapolated voltage. By incorporating temperature compensation factors into the extrapolation calculation, the method prevents transient temperature effects from being misinterpreted as voltage decay, thereby maintaining measurement precision while still compensating for temperature dependence.
Solution Approach 2:
The patent uses polarization voltage as an intermediary parameter to separate and compensate for temperature effects. By measuring current and calculating polarization voltage, the method isolates the temperature-dependent component from the total voltage measurement, allowing accurate compensation without misinterpreting transient processes. This intermediary approach enables precise no-load voltage determination even during temperature changes.
3Object-affected harmful factors
If polarization voltage compensation is performed after extrapolation, then current effects are compensated, but measurement precision deteriorates due to superimposed transient processes
Solution Approach 1:
The patent applies preliminary action by calculating and applying polarization voltage compensation during the voltage decay extrapolation process, before the final open-circuit voltage is determined. By measuring current at multiple time points and extrapolating the polarization voltage decay simultaneously with the terminal voltage, the method compensates for current effects in advance, preventing transient polarization processes from contaminating the final measurement and thereby maintaining high precision.
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 reduces errors in determining the no-load voltage, providing a more robust and accurate method that is less affected by environmental changes and transient processes, leading to improved state of charge estimation.
Implementation Method 1
an electrochemical energy store, for example a lead-acid battery
Implementation Method 2
the no-load voltage sets in at different speeds... the measured battery voltage values are extrapolated to a stationary value
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for the determination of the off-load voltage of an electrochemical energy store in which the off-load voltage is determined by means of an extrapolation method taking into consideration voltage values compensated for temperature, current, and load.