Battery EIS Circuit Using Energy Reinjection for SOC and SOH
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Solution Overview
Problem
Existing battery characterization methods using Electrochemical Impedance Spectroscopy (EIS) face drawbacks, such as the need for external voltage sources and inefficiencies in measuring frequency domain impedance, which affect precise state of charge (SOC) and state of health (SOH) estimation.
Innovation Solution
An EIS measuring device comprising an electrical energy storage circuit and an electronic circuit configured to alternately circulate charge and discharge currents as a modulated sinusoidal signal between the battery and the circuit, allowing for impedance measurement without external energy sources, and calculating SOC and SOH from the impedance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external voltage sources are used for EIS measurement, then impedance measurement can be performed, but device complexity and energy consumption increase
Solution Approach 1:
The battery management system performs EIS measurements using its own existing components (power converter, capacitor, current sensor, voltage sensor) without requiring external voltage sources or dedicated EIS measurement hardware. The system serves itself by utilizing its operational components for dual purposes: power management and impedance characterization.
Solution Approach 2:
The power converter and capacitor, originally designed for battery charging/discharging operations, are made multi-functional by enabling them to also serve as the excitation source and energy storage element for EIS measurements. This eliminates the need for separate dedicated EIS measurement hardware.
2Measurement precision
If traditional EIS measurement methods are used, then impedance data can be obtained, but energy efficiency decreases due to continuous external power supply
Solution Approach 1:
The system applies periodic AC excitation signals through the power converter to generate the alternative current needed for EIS measurements. This periodic action allows impedance characterization without requiring continuous external power supply, improving energy efficiency by using pulsed rather than continuous excitation.
Solution Approach 2:
The system uses its own operational components (power converter switching cycles, existing capacitor) to generate excitation signals, eliminating the need for separate external power sources and reducing overall energy consumption of the measurement system.
3Measurement precision
If dedicated EIS measurement hardware is added, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
Existing BMS components (power converter, capacitor, current sensor, voltage sensor) are made multi-functional to perform both their original battery management functions and EIS measurement functions. This eliminates the need for dedicated EIS measurement hardware while maintaining measurement capabilities.
Solution Approach 2:
The EIS measurement function is merged with the existing battery management system operations. The power converter serves dual purposes: power management and EIS excitation source. The capacitor serves dual purposes: energy storage and EIS reference element. This consolidation eliminates redundant hardware.
4Ease of operation
If alternative current circulation is implemented, then impedance measurement is enabled without external sources, but control complexity increases
Solution Approach 1:
The power converter, already present in the battery management system for normal operations, is utilized to generate and control the alternative current for EIS measurements. This self-service approach enables the system to perform impedance measurements independently without external voltage sources, while leveraging existing control infrastructure.
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 solution enables precise characterization of battery SOC and SOH with improved efficiency and without the need for external energy sources, enhancing battery management systems by accurately measuring impedance and state parameters.
Implementation Method 1
an electrical energy storage circuit; wherein the electronic circuit is alternately configured in a first mode to pull out electrical energy of the battery and storing the electrical energy pulled-out from the battery in the electrical energy storage circuit
Data Source
Figure 1~2
Figure 3a~3c
Figure 4a~4b
AI summary
The present disclosure relates to an EIS measuring device (100) comprising: - an electrical energy storage circuit (102); - an electronic circuit (104) coupled to the electrical energy storage circuit and configured to be coupled to a battery (106) whose impedance is to be measured by the EIS measuring device, - a characterization circuit (108) configured to measure an alternative current intended to circulate between the battery and the electronic circuit, and a voltage at terminals of the battery; wherein the electronic circuit is alternately configured in a first mode to pull out electrical energy of the battery and storing the electrical energy pulled-out from the battery in the electrical energy storage circuit, and in a second mode to pull out the stored electrical energy from the electrical energy storage circuit and to re-inject the electrical energy pulled-out from the electrical energy storage circuit in the battery.