Battery Cell Monitoring Circuit for FET Switching Verification
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Solution Overview
Problem
Existing battery management systems struggle to reliably monitor battery cells connected in series, especially under load, due to difficulties in distinguishing voltage differences caused by switching elements from those caused by electrical loads, leading to potential irreversible damage and overheating.
Innovation Solution
A device with measuring circuits and a control unit that switches electrical loads in parallel to battery cells, using voltage differences to determine correct operation of switching elements, and incorporates RC circuits to filter noise and detect electrical interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage difference sensing is used to detect FET switching, then switching status can be monitored, but it becomes difficult to distinguish switching-induced voltage differences from load-induced voltage differences
Solution Approach 1:
The patent segments the voltage difference detection into two distinct components: a first voltage difference caused by FET switching and a second voltage difference caused by electrical load. By separately identifying and measuring these two components, the system can distinguish between switching status and load conditions, resolving the ambiguity in voltage difference sensing.
Solution Approach 2:
The patent introduces an intermediary approach by using the third battery cell's voltage as a reference to calculate the load-induced voltage difference. This intermediary measurement allows the system to subtract the load component from the total voltage difference, isolating the FET switching component for accurate detection.
2Stability of the object's composition
If passive equalization through resistive elements is used, then battery cell state of charge can be equalized, but correct connection and switching of components becomes difficult to verify
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage differences across battery cells and comparing them against expected values. The control unit uses this feedback information to verify whether FETs are switching correctly and whether resistive elements are properly connected, enabling real-time verification of component operation during passive equalization.
Solution Approach 2:
The patent performs preliminary verification actions by measuring voltage differences before and during equalization processes. This preliminary measurement establishes a baseline for comparing component behavior, allowing the system to detect anomalies in FET switching or resistive element connection before they cause equalization failures.
3Productivity
If battery cells are monitored under electrical load, then real-time battery status can be assessed, but voltage measurements become unreliable due to load-induced voltage drops
Solution Approach 1:
The patent extracts the load-induced voltage component from the total measured voltage difference. By calculating the voltage drop across the electrical load separately and subtracting it from the total voltage difference, the system isolates the FET switching component, enabling accurate monitoring even under electrical load conditions.
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 reliable monitoring of battery cells under load by accurately determining switching element functionality and detecting electrical interruptions, preventing damage and overheating.
Implementation Method 1
In a further development, each measuring circuit has an RC circuit, in particular a low-pass filter
Implementation Method 2
each measuring circuit has an RC circuit
Implementation Method 3
The voltage difference results from the fact that the electrical load, the switching element, and the power that connect the aforementioned elements to the battery cells form a voltage divider
Implementation Method 4
a controllable switching element with which the electrical load can be connected into a path parallel to the battery cell associated with the measuring circuit
Data Source
AI summary
A device for monitoring at least three battery cells connected in series. The device includes, for each battery cell, a measuring circuit associated with the battery cell, which measuring circuit has an electrical load and can be switched by a controllable switching element such that the electrical load can be connected into a path parallel to the battery cell associated with the measuring circuit. A control unit that is designed to switch a first measuring circuit, which is associated with the first battery cell, and a third measuring circuit, which is associated with the third battery cell, such that the electrical loads of the two measuring circuits are each connected into the path parallel to the battery cell associated with the respective measuring circuit, and to ascertain whether the switching element of the first measuring circuit is switching correctly.