Loaded-Vent Safety Bag for E-Bike Battery Thermal Runaway
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Solution Overview
Problem
Current solutions for storing and transporting high-capacity e-bike lithium-ion batteries, such as those with 400-1100 Wh energy capacity, are inadequate as they fail to prevent rupture or explosion during thermal runaway, posing safety risks due to rapid pressure buildup and dispersal of high-temperature materials.
Innovation Solution
A fire and explosion-resistant storage and transport bag designed with multiple layers of fire-resistant and thermal insulation materials, featuring high-temperature vents loaded with fire-resistant materials like steel wool to vent gases while blocking flames, and stitched with thermally stable yarns to prevent rupture, allowing for controlled release of smoke and heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aviation grade fire containment bags are used to contain e-bike batteries, then fire resistance is improved, but the bag ruptures or explodes due to rapid pressure buildup during thermal runaway
Solution Approach 1:
The bag is divided into multiple functional layers: an inner fire-resistant layer (PBI-coated polyester) for thermal protection, an intermediate reflective aluminum layer for heat reflection, and an outer fire-resistant layer (Nomex) for structural integrity. This segmentation allows each layer to specialize in resisting different aspects of thermal runaway.
Solution Approach 2:
The bag incorporates a pressure-regulating valve that opens at a specific pressure threshold during thermal runaway, allowing controlled venting of gases and flames. This parameter-based control prevents uncontrolled pressure buildup while maintaining fire resistance through the multi-layer structure.
2Reliability
If the bag is made completely fire-resistant and sealed, then fire protection is improved, but thermal runaway pressure cannot be released causing bag rupture
Solution Approach 1:
The pressure-regulating valve acts as an intermediary mechanism between the sealed fire-resistant bag and the external environment. It selectively releases pressure and flames while maintaining the overall fire-resistant barrier, preventing uncontrolled rupture while allowing safe venting.
Solution Approach 2:
The harmful pressure buildup and flames generated during thermal runaway are converted into a controlled venting process. The pressure-regulating valve directs flames and gases through a controlled path, and the reflective aluminum layer redirects heat away from critical areas, transforming the destructive thermal runaway into a manageable event.
3Strength
If the bag uses thick fire-resistant materials to prevent rupture, then strength is improved, but flexibility and ease of operation deteriorate
Solution Approach 1:
The bag employs a composite structure combining three different materials: PBI-coated polyester for fire resistance, reflective aluminum for heat reflection, and Nomex for structural strength and flexibility. This composite approach achieves high rupture resistance while maintaining operational flexibility that single thick materials cannot provide.
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 bag effectively contains thermal runaway events in e-bike batteries by preventing rupture and explosion, allowing for controlled venting of gases and smoke, thereby reducing consequential damage and ensuring safety during transportation and storage.
Implementation Method 1
the steel wool is allowed to react with venting products through oxidation
Implementation Method 2
the body of the bag is formed of multiple layers of fire resistant and thermal insulation materials designed for resisting the thermal energy
Implementation Method 3
the bag comprises a high temperature vent suitable for venting gasses from the inner volume to the environment
Data Source
AI summary
A fire resistant safety bag comprising a body that defines an internal volume for carrying and storing a lithium ion battery having a maximum energy capacity between 250-1250 Wh, such as 750 Wh, wherein the body of the bag is formed of multiple layers of fire resistant material designed for resisting the thermal energy contained in a 50% charged 750 Wh Lithium-ion battery, and wherein the layers of fire resistant material are jointly flexible for allowing one end of the bag to be folded between an open and a closed position for reversibly closing off the internal volume against manual access, wherein the bag comprises a high temperature first vent suitable for venting gasses from the inner volume to the environment, said first vent being loaded with a fire resistant material forming a filter.