EV Battery Impedance Detection Using Inverter-Generated Ripple Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for testing battery impedance in electric vehicles face challenges due to low internal resistance and low voltage ripple, making it difficult to accurately measure battery state and estimate service life.
Innovation Solution
A method that generates ripple current using an inverter and motor to measure battery impedance, involving the activation of a detection model based on vehicle speed, motor speed, state of charge, and temperature, and using fast Fourier transform to calculate impedance magnitude and phase differences between battery cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional impedance testing methods are used on batteries with low internal resistance, then measurement is required to check battery state, but measurement precision deteriorates due to low voltage ripple making it difficult to accurately measure battery state and estimate service life
Solution Approach 1:
The patent applies electrical vibration (ripple current) to the battery system to enable measurement. By introducing a small-amplitude alternating current signal through the inverter and motor system, the patent creates measurable voltage fluctuations across the battery terminals, transforming an otherwise static low-ripple condition into a dynamic measurable state that reveals impedance characteristics.
Solution Approach 2:
The patent uses the motor and inverter as intermediary components to generate the test signal. Rather than directly injecting current into the battery, the system uses the motor-inverter assembly to convert mechanical energy back into electrical ripple current, which then flows through the battery. This intermediary approach enables non-contact, online impedance measurement without requiring direct battery terminal modifications.
2Ease of operation
If ripple current is generated using inverter and motor to measure battery impedance, then online measurement during normal driving is enabled, but device complexity increases due to requiring coordination of multiple vehicle components
Solution Approach 1:
The patent makes the motor and inverter serve dual functions: their primary function of propelling the vehicle and their secondary function of generating test ripple current for battery impedance measurement. By controlling the inverter to operate in a specific mode during normal driving, the system simultaneously achieves vehicle propulsion and battery testing without requiring separate dedicated testing equipment.
Solution Approach 2:
The vehicle's own powertrain components (motor and inverter) are used to perform the battery testing function. The system leverages existing operational cycles and component capabilities to generate the necessary test signals, allowing the vehicle to self-test its battery health during normal operation without external intervention or additional specialized equipment.
3Measurement precision
If fast Fourier transform is used to calculate impedance magnitude and phase differences, then measurement precision is improved, but loss of time increases due to computational processing requirements
Solution Approach 1:
The patent performs Fast Fourier Transform analysis on voltage and current waveforms that have already been captured during normal driving operation. By processing the data after collection rather than requiring real-time analysis during the measurement window, the system can apply computationally intensive FFT algorithms to extract precise impedance and phase information from the recorded ripple signals without extending the actual testing duration.
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
Enables accurate online measurement of battery impedance during normal driving conditions, improving the assessment of battery health and safety by reducing noise impact and maintaining motor balance.
Implementation Method 1
generates a ripple current by controlling an inverter and a motor
Implementation Method 2
using fast Fourier transform to calculate impedance magnitude and phase differences between battery cells
Data Source
AI summary
A method of detecting safe and other states of battery while electric vehicle is being driven controls an inverter to generate ripple current on the battery; ripple voltages of a plurality of battery cells are measured, voltage phase shifts between the battery cells are calculated. The battery can be analyzed as normal or otherwise according to the voltage phase shift between plurality of the battery cells. A vehicle-mounted device and a non-volatile storage medium therein, for performing the above-described method, are also disclosed.