Thermal Frangible Bulb Current Interrupt Device
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Solution Overview
Problem
Existing current interrupt devices (CIDs) for electrochemical cells, such as lithium-ion batteries, are complex and costly, and often lead to catastrophic failures due to gas exposure when interrupting current flow, as they rely on internal pressure rather than thermal activation.
Innovation Solution
A thermally triggered current interrupt device using a frangible bulb that breaks at a temperature threshold, disconnecting the electrical circuit to prevent overcharging, overvoltage, and thermal runaway, with a diode and heating element to control heating and ensure safe disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal pressure is used to interrupt current flow, then current interruption is achieved, but gas exposure and catastrophic failure occur
Solution Approach 1:
The patent replaces the mechanical pressure-based interruption system with a thermal field-based system. A thermally responsive frangible bulb breaks when exposed to thermal runaway temperatures, mechanically separating the electrical contacts to interrupt current flow. This substitution eliminates gas exposure while achieving reliable current interruption through thermal activation rather than pressure mechanisms.
Solution Approach 2:
The frangible bulb acts as an intermediary element between the thermal runaway condition and the electrical contact separation. The bulb contains the breaking contact in normal operation and, when thermally activated, breaks to allow spring-driven separation of contacts. This intermediary mechanism prevents direct exposure to harmful gases while reliably achieving current interruption.
2Reliability
If redundant monitoring systems are added, then safety is improved, but complexity and cost increase significantly
Solution Approach 1:
The CID device provides self-service safety functionality by directly responding to thermal runaway conditions through the frangible bulb's thermal activation. The device autonomously interrupts current flow when temperature thresholds are exceeded, eliminating the need for external redundant monitoring systems. This self-service approach maintains safety while reducing overall system complexity.
Solution Approach 2:
The frangible bulb-based CID serves multiple safety functions simultaneously: it detects thermal runaway conditions, triggers current interruption, and prevents catastrophic failure all through a single integrated mechanism. This multi-functionality replaces what would otherwise require multiple separate monitoring and response systems, reducing complexity while maintaining comprehensive safety.
3Measurement precision
If frangible bulb is positioned close to electrochemical cell, then response accuracy is improved, but thermal activation sensitivity increases
Solution Approach 1:
The frangible bulb is designed with specific thermal properties including a glass transition temperature and internal pressure characteristics that define its activation threshold. By positioning the bulb close to the electrochemical cell and engineering its thermal response parameters, the system achieves accurate detection of genuine thermal runaway conditions while the controlled parameter changes prevent activation from normal temperature fluctuations.
Solution Approach 2:
The frangible bulb incorporates a spring mechanism that provides cushioning and controlled response. The spring maintains contact pressure during normal operation and provides a controlled separation force when the bulb breaks. This beforehand cushioning ensures that only genuine thermal runaway events trigger activation, preventing false responses to minor temperature variations while maintaining high detection 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
The solution effectively prevents catastrophic failures by thermally activating the CID, ensuring safe disconnection of electrical current and reducing the complexity and cost associated with traditional CIDs, while maintaining reliability and safety.
Implementation Method 1
the frangible bulb is configured to break at a temperature threshold
Implementation Method 2
the CID can include a resistor configured to heat the frangible bulb to above the temperature threshold when the current through the breaking contact reaches a current threshold
Data Source
AI summary
Embodiments described herein relate generally to a current interrupt device (CID) including a frangible bulb that is configured to be thermally triggered. In some embodiments, the CID includes a breaking contact electrically coupled to a fixed contact and held in electrical contact by the frangible bulb. In some embodiments, the frangible bulb is configured to break at a temperature threshold. In some embodiments, the breaking contact is configured to bend, rotate and/or otherwise deform about a hinge point in order to become electrically disconnected from the fixed contact when the frangible bulb breaks. In some embodiments, opening the electrical circuit between the breaking contact and the fixed contact may prevent overcharging, overvoltage conditions, overcurrent conditions, thermal runaway, and/or other catastrophic failure events.