Cell Supervisory Controller Diagnostic Circuit for Voltage Measurement
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Solution Overview
Problem
Lithium-ion batteries used in electric vehicles are susceptible to temperature variations and overcharge/overdischarge damage, posing challenges for reliable operation and safety, and existing systems struggle to accurately detect failures in voltage monitoring circuits, which can lead to irreversible damage.
Innovation Solution
A battery system with a diagnostic circuit and cell supervisory controller that includes a cell discharge circuit and microcontroller to validate proper operation of voltage measurement systems, activating the discharge circuit to identify floating voltages and treat failed measurements as zero voltage, ensuring accurate voltage monitoring and preventing overcharge/overdischarge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage monitoring circuits are used to monitor each cell, then overcharge/overdischarge protection is improved, but the ability to detect floating voltages and measurement accuracy deteriorates
Solution Approach 1:
The system performs preliminary actions by periodically activating discharge circuits to discharge cells before taking voltage measurements. This preliminary discharge action eliminates floating voltage conditions and ensures accurate measurements by establishing a known reference state before measurement occurs.
Solution Approach 2:
Discharge circuits are introduced as intermediary components between the voltage monitoring system and the battery cells. These intermediaries actively manage the electrical state of cells prior to measurement, preventing floating voltage conditions and enabling accurate voltage readings by mediating the interaction between monitoring circuits and battery cells.
2Device complexity
If simple voltage monitoring is used, then device complexity is reduced, but the ability to detect and diagnose cell failures deteriorates
Solution Approach 1:
The system performs preliminary diagnostic actions by periodically activating discharge circuits to test cell responses. This preliminary testing action enables detection of cell failures and measurement system faults without requiring complex continuous monitoring, achieving diagnostic capability through periodic active testing rather than complex passive monitoring.
Solution Approach 2:
The monitoring system performs self-diagnosis by using the discharge circuits to actively test both cell health and measurement system functionality. The system serves itself by incorporating self-testing capabilities that automatically detect failures in both the battery cells and the monitoring infrastructure without external intervention.
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A system for assessing the accuracy of an electrochemical cell voltage measurement includes a cell discharge circuit electrically coupled to at least one electrochemical cell and configured to partially discharge the at least one cell when the cell discharge circuit is activated, and a cell measurement circuit electrically coupled to the at least one cell and to the cell discharge circuit. The cell measurement circuit is configured to measure a voltage of the at least one cell before activation of the cell discharge circuit and after activation of the cell discharge circuit. The cell measurement circuit compares the voltage before activation of the cell discharge circuit to the voltage after activation of the cell discharge circuit to detect if an error in the voltage measurement occurred.