Active Balancer Impedance Measurement Using Multi-Tone Disturbances
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Solution Overview
Problem
Existing battery impedance measurement techniques are limited to offline laboratory settings, are not cost-effective, and do not allow for simultaneous cell balancing and impedance measurement in battery packs with series connections, leading to inefficiencies and potential battery cycle life shortening due to ripple currents.
Innovation Solution
The integration of active balancer electronic systems that leverage existing DC/DC converters to perform both cell balancing and impedance measurement in-situ and online, using controlled disturbances in the switching waveform to minimize load ripple and enable accurate impedance measurement at various frequencies without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active balancing circuits are used to balance battery cells, then cell balancing performance is improved, but device complexity increases due to additional electronic components
Solution Approach 1:
The patent makes the active balancing circuit perform dual functions: cell balancing and impedance measurement. The existing DC/DC converters in the active balancing circuit are utilized to inject test signals and measure impedance, eliminating the need for separate impedance measurement hardware and reducing overall device complexity.
Solution Approach 2:
The patent combines the cell balancing function and impedance measurement function into a single integrated system. The active balancing circuit's DC/DC converters are merged with impedance measurement capabilities, allowing both functions to share the same hardware infrastructure.
2Measurement precision
If separate impedance measurement hardware is used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The active balancing circuit is designed to perform both cell balancing and impedance measurement functions. The DC/DC converters used for balancing are also utilized to generate test signals and measure impedance, making the circuit multi-functional and eliminating the need for separate measurement hardware.
Solution Approach 2:
The active balancing circuit serves itself by using its own DC/DC converters to perform impedance measurements. The circuit leverages its existing components to measure impedance without requiring external or dedicated measurement equipment, reducing hardware complexity while maintaining measurement capability.
3Measurement precision
If traditional impedance measurement methods are used, then measurement accuracy is improved, but productivity decreases due to offline laboratory settings and system downtime
Solution Approach 1:
The patent performs impedance measurements continuously in the background during normal battery operation. The active balancing circuit injects small test signals and measures impedance without stopping the battery system, allowing measurements to be taken in advance and continuously rather than requiring offline laboratory testing.
Solution Approach 2:
The impedance measurement process is made continuous and operates concurrently with normal battery charging and discharging operations. The measurement system works continuously without interrupting battery usage, maintaining productivity while providing ongoing impedance monitoring.
4Productivity
If active balancing circuits are used, then cell balancing efficiency is improved, but loss of energy increases due to ripple currents
Solution Approach 1:
The patent uses real-time impedance measurement feedback to optimize the active balancing process. By continuously monitoring cell impedance, the system can adjust balancing operations to minimize harmful ripple currents while maintaining efficient charge redistribution, reducing energy loss and stress on battery cells.
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 allows for accurate, cost-effective, and efficient impedance measurement of battery cells in series connections, enabling real-time monitoring and minimizing system downtime, while also balancing cells to extend battery life by reducing ripple-induced stress.
Implementation Method 1
active balancing typically moves charge from one cell to another, for instance, moving charge from a cell that has more charge to a cell that has less charge
Implementation Method 2
The response is digitized and processed via an internal DSP engine. The AD5933 operates in potentiostatic mode i.e., generates a voltage signal and measures current to obtain impedance
Data Source
AI summary
The present disclosure relates to methods and systems for management and control of interconnected energy storage modules, such as battery packs, that can form a larger energy storage system. The disclosure also relates to methods and system for the measurement of cell impedances in a battery pack in-situ and on-line and using active balancing circuits that may already be present in the battery pack. The methods and systems can inject disturbances of different frequencies and measure impedance by using the active balancing circuits present in the battery pack, which can transform an active balancer into a dual active balancer and impedance measurement system. The speed up of impedance measurement energy storage modules can be accomplished by using multi-tone, orthogonal or spread spectrum waveforms applied simultaneously on all or a sub-set of the active balancer circuits in an active balancer.