Battery Voltage Prediction Using Dynamic RC Parameters
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Solution Overview
Problem
Current battery voltage prediction models face challenges in accurately simulating battery output voltage due to non-linear characteristics affected by temperature, capacity, and internal resistance, particularly when predicting voltage changes over long timescales, such as during the hybrid pulse power characterization (HPPC) discharge test, which struggles to simulate ion transfer occurring over extended periods.
Innovation Solution
A battery voltage prediction apparatus and method that utilize an equivalent circuit model with variable resistors and capacitors, along with tuning parameters, to predict battery output voltage over time by deriving fixed and tuning parameters based on measured voltages and current applications, allowing for accurate modeling of battery voltage changes due to ion transfer over extended periods without adding RC branches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chemical reaction-based model is used to simulate battery, then the model can capture non-linear characteristics, but the operation speed becomes slow
Solution Approach 1:
The patent replaces the chemical reaction-based model with an equivalent circuit model that uses electrical components (resistors, capacitors, voltage sources) to simulate battery behavior. This substitution maintains the ability to capture non-linear characteristics while significantly improving operation speed, as electrical circuit calculations are computationally more efficient than chemical reaction simulations.
Solution Approach 2:
The patent introduces time-varying parameters (resistance and capacitance values that change with state of charge and temperature) into the equivalent circuit model. This allows the model to accurately represent the non-linear characteristics of the battery across different operating conditions while maintaining the computational efficiency of the circuit-based approach.
2Device complexity
If an equivalent circuit model with fixed parameters is used, then the model structure is simple, but the prediction reliability deteriorates when current amount and application time vary
Solution Approach 1:
The patent transforms the static equivalent circuit model with fixed parameters into a dynamic model where resistance and capacitance values vary with the state of charge and temperature of the battery. This dynamic adaptation allows the model to maintain high prediction reliability across different current amounts and application times while keeping the overall model structure relatively simple.
Solution Approach 2:
The patent implements parameter changes by making the resistance and capacitance values functions of state of charge and temperature rather than constant values. This enables the equivalent circuit model to accurately predict battery voltage under varying operating conditions without requiring a complex model structure.
3Measurement precision
If multiple RC branches are added to the equivalent circuit model, then the prediction accuracy improves, but the parameter extraction process becomes complicated and calculation time increases
Solution Approach 1:
The patent segments the parameter extraction process into two distinct phases: a calibration phase where comprehensive data is collected to determine the functional relationships between parameters and operating conditions, and an operational phase where these pre-determined relationships are applied directly. This segmentation reduces the complexity of real-time parameter extraction while maintaining high prediction accuracy.
Solution Approach 2:
The patent performs preliminary characterization of the battery to establish the relationships between resistance/capacitance values and state of charge/temperature before actual operation. This preliminary action creates lookup tables or functional models that can be quickly referenced during operation, avoiding the need for complex real-time parameter extraction while maintaining accuracy.
4Loss of time
If HPPC discharge test with 10 seconds charge/discharge current is used, then the test duration is short, but the voltage change due to ion transfer cannot be simulated
Solution Approach 1:
The patent uses a dynamic equivalent circuit model where resistance and capacitance values are continuously updated based on the state of charge and temperature, allowing the model to accurately simulate the voltage changes due to ion transfer even during short-duration HPPC tests. The dynamic parameters capture the transient behavior that would otherwise require long test durations to observe.
Solution Approach 2:
The patent changes the parameters of the equivalent circuit model (resistance and capacitance) as functions of state of charge and temperature, enabling the model to simulate the voltage diffusion effects of ion transfer on short timescales. This parameter adaptation allows accurate voltage prediction during brief HPPC discharge tests without requiring extended test durations.
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 enhances the accuracy and reliability of battery voltage prediction, simplifies the parameter extraction process, and reduces calculation time, effectively simulating voltage changes during long-term charging and discharging, improving the prediction of battery output voltage for eco-friendly vehicles.
Implementation Method 1
A battery is a device configured to generate electrical energy by a chemical reaction
Implementation Method 2
The transfer of ions occurs over a relatively long time... voltage change (diffusion) due to the transfer of ions
Data Source
AI summary
A battery voltage prediction apparatus may include: a state-of-charge (SOC) derivation unit configured to derive the SOC of a battery according to a current that is input or output to the battery and a capacity of the battery; a fixed parameter derivation unit configured to derive fixed parameters required for an equivalent circuit model based on voltages measured according to input/output currents of the battery and a time change within a preset time when the current is input or output for the preset time; and a tuning parameter derivation unit configured to derive at least one tuning parameter that varies depending on a time required for the equivalent circuit model when the current is input or output for a time exceeding the preset time.