Distributed Battery Monitoring for Asynchronous Impedance Measurement
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Solution Overview
Problem
Existing battery monitoring systems face challenges in accurately determining complex impedance without shared clock signals or precision oscillators, leading to difficulties in obtaining phase and timing information, which is crucial for precise SoC and SoH estimation.
Innovation Solution
A battery monitoring system that utilizes a controller, current and voltage measurement devices connected via a DC isolated bus, compensates for asynchrony between these components using initial calibration and asynchrony compensation methods, enabling accurate complex impedance determination across multiple integrated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple integrated circuits are used for measuring DC voltage and DC current without a shared clock signal, then device complexity is reduced and cost is lowered, but measurement precision deteriorates due to inability to obtain accurate phase and timing information
Solution Approach 1:
The system performs preliminary calibration measurements to characterize the asynchrony between independent oscillators before actual impedance measurements. By measuring the time offset and frequency difference between oscillators in advance, the system can compensate for these differences during subsequent measurements, enabling accurate complex impedance determination without requiring shared clock signals.
Solution Approach 2:
The system uses feedback from calibration measurements to adjust and compensate for asynchrony between independent oscillators. The measured time offsets and frequency differences are fed back into the measurement process to correct phase and timing information, allowing precise impedance measurement despite using independent oscillator sources in each integrated circuit.
2Measurement precision
If a shared clock signal is distributed across multiple voltage levels, then measurement precision improves through synchronized timing, but device complexity increases due to expensive clock bus infrastructure
Solution Approach 1:
The system segments the clocking function by allowing each integrated circuit to use its own independent oscillator rather than requiring a unified shared clock signal. This segmentation enables independent operation of measurement devices across different voltage levels while maintaining measurement accuracy through asynchrony compensation techniques that account for individual oscillator characteristics.
Solution Approach 2:
The system introduces an intermediary calibration and compensation mechanism that mediates between independent oscillators. By measuring and characterizing the relationships between independent clock sources through calibration procedures, the system creates a virtual synchronization that eliminates the need for physical clock signal distribution infrastructure.
3Measurement precision
If precision oscillators are included in economically designed circuits, then measurement precision improves, but manufacturing cost increases
Solution Approach 1:
The system replaces expensive precision oscillators with inexpensive standard oscillators in each integrated circuit. By using cheaper oscillator components and compensating for their imperfections through calibration and software-based asynchrony compensation, the system achieves the same measurement precision at lower manufacturing cost, making the solution economically viable for mass production.
Data Source
AI summary
A system for measuring a complex impedance associated with an arrangement of battery or fuel cells in an energy storage system may include a controller, a current measurement device, and voltage measurement devices. The current measurement device may be shared by the cells for measuring a test current provided to the cells. The voltage measurement devices may be respectively coupled across corresponding cells. The controller, the current measurement device, and the voltage measurement devices may be coupled together using a DC isolated bus. The controller may determine a respective complex impedance of corresponding groups of the cells using a complex voltage measured by a respective voltage measurement device coupled across a corresponding group of the cells and a complex current measured by the complex current measurement device. The controller may be configured to compensate for an asynchrony between particular ones of the current measurement device and the voltage measurement devices via the DC isolated bus.