Battery String Fuse State Detection Using Parallel Resistor Switching
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Solution Overview
Problem
Existing battery management systems struggle to rapidly and reliably determine the state of fuses in battery packs without string contactors, leading to potential overloading of remaining active strings when a fuse is blown, and existing methods require power and are not applicable before battery use.
Innovation Solution
A method involving a battery pack with a first string containing a fuse, a resistor, and an ammeter, where the resistor is switchable between connected and disconnected states, allowing current measurement to determine if the fuse is intact by measuring current changes after switching the resistor to a connected state, enabling pre-use fuse state determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing methods (cell balancing frequency tracking) are used to determine fuse state, then fuse state can be determined, but the determination is slow and cannot be performed before battery use
Solution Approach 1:
The patent connects a resistor in parallel with the battery cell before the battery is put into service. This preliminary configuration enables immediate fuse state determination upon connection to a load, eliminating the need for time-consuming cell balancing frequency tracking and allowing pre-use fuse assessment.
Solution Approach 2:
The patent introduces a resistor as an intermediary component connected in parallel with the battery cell. This resistor serves as a mediator that enables current flow measurements to determine fuse state, providing a direct and rapid assessment method without relying on indirect cell balancing observations.
2Reliability
If string contactors are installed in each string to detect fuse state, then the number of online strings can be determined, but the device complexity increases
Solution Approach 1:
The patent makes the previously unused parallel resistor serve multiple functions: it acts as a ballast resistor for normal operation and simultaneously serves as a measurement tool for fuse state determination. This multi-functionality eliminates the need for separate string contactors or additional detection devices.
Solution Approach 2:
The patent enables the battery pack's existing components (parallel resistor and ammeter) to perform the additional function of fuse state detection. The system uses its own operational current measurements to determine fuse integrity, eliminating the need for external detection devices or increased system complexity.
3Device complexity
If all strings are assumed online without string contactors, then the device complexity is low, but the current limits are not adjusted and overloading risk increases
Solution Approach 1:
The patent implements a feedback mechanism where the ammeter continuously monitors current through the parallel resistor, and the BMS uses this information to determine fuse state and adjust current limits accordingly. This feedback loop ensures accurate current limit management without requiring complex additional hardware.
Solution Approach 2:
The patent replaces the mechanical string contactor system with an electrical measurement approach using the existing ammeter and parallel resistor. Instead of mechanical switches to isolate strings, the system uses electrical current measurements to detect fuse state and software-based current limit adjustments, reducing mechanical complexity.
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 method allows for rapid and reliable determination of fuse states before battery connection, enabling adjustment of current limits to prevent overloading and ensuring safe operation, applicable to battery packs with one or more battery cells per string.
Implementation Method 1
a first string further comprising at least one parallel arrangement comprising a battery cell and a resistor, wherein the parallel arrangement is configured to be changeable between a connected state wherein the resistor is connected in parallel to the battery cell
Implementation Method 2
measuring a first current passing through the first string using the first ammeter during a first time period after the at least one parallel arrangement is changed to the connected state
Data Source
AI summary
A method for determining a state of a fuse in a battery pack is provided. The battery pack comprises a first string comprising a first string fuse; at least one parallel arrangement comprising a battery cell and a resistor; and a first ammeter. The parallel arrangement is configured to be changeable between a connected state wherein the resistor is connected in parallel to the battery cell and a disconnected state wherein the resistor is disconnected from the battery cell. A second string comprising at least one battery cell is connected in parallel to the first string. The method comprises changing the at least one parallel arrangement of the first string to the connected state, and measuring a current passing through the first string. In an event that the change in the first current does not exceed a threshold, the first string fuse is in a blown state.