Battery Cell Measurement Circuit for Open-Load Detection During Balancing
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Solution Overview
Problem
Existing battery management systems (BMS) face challenges in accurately detecting open loads during cell balancing, which can lead to inefficiencies and reduced battery capacity due to state of charge and capacity/energy mismatches between cells.
Innovation Solution
The implementation of a multi-cell battery apparatus with voltage-stacked battery cell circuits and a control circuit that selectively activates switchable resistive-divider circuits to measure controlled-load voltage drops, allowing for open load detection without interfering with cell balancing or redundant measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cell balancing is performed by drawing large current through a resistor, then cell balancing effectiveness is improved, but power dissipation increases requiring external resistors
Solution Approach 1:
The patent extracts the balancing resistor from the IC chip and places it externally. The IC chip contains only the control switch, while the resistor is implemented outside the chip. This separation reduces the IC chip's power dissipation and allows for more effective cell balancing without overheating the integrated circuit.
2Reliability
If open load detection is implemented to check cell balancing pin connections, then diagnostic capability is improved, but measurement accuracy may be compromised
Solution Approach 1:
The patent performs open load detection before normal cell balancing measurements. The control switch is configured to connect the cell balancing pin to ground through a detection resistor during a preliminary detection phase, allowing the system to verify proper connections before switching to normal balancing operation, thus preventing measurement errors.
Solution Approach 2:
The system periodically alternates between open load detection mode and normal cell balancing mode. The control switch toggles between connecting to ground through the detection resistor and connecting to the external balancing resistor, enabling periodic verification of connection integrity without continuously compromising measurement accuracy.
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 accurate open load detection, ensuring proper cell balancing and maintaining measurement accuracy, thereby extending battery functionality and maximizing battery capacity.
Implementation Method 1
a switchable resistive-divider circuit having an input node disposed between the upper voltage terminal and the lower voltage terminal, for providing an output corresponding to a controlled-load voltage drop
Data Source
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AI summary
A multi-cell battery apparatus is provided, according to certain aspects, including a battery with a plurality of voltage-stacked battery cell circuits (102a, 102b), a switchable resistive-divider circuit (105) and a control circuit (104). The control circuit selectively activates the switchable resistive-divider circuits and, in response to the respective switchable resistive-divider circuits (105) being selectively activated, the control circuit measures the controlled-load voltage drops. These aspects are used to allow open load detection without interfering with the cell balancing mechanism and the accuracy of the redundant measurements performed on these pins in a battery management system.