Battery Housing Degassing Membrane for Low-Pressure Venting
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Solution Overview
Problem
Existing degassing units for battery housings, particularly in traction batteries of motor vehicles, require efficient pressure relief at low degassing pressures while preventing foreign body ingress and maintaining structural integrity, which is challenging due to limitations in materials and installation space.
Innovation Solution
A degassing unit featuring a film composite membrane with a first film having minimal elongation and a second film with high elongation, where the second film is reinforced by the first film's cutouts to achieve low degassing pressure release without significant stroke movement, allowing for adjustable burst pressure and reduced installation space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a single membrane is used for degassing, then the structure is simple, but the burst pressure cannot be sufficiently reduced
Solution Approach 1:
The patent applies composite materials by combining a first film with minimal elongation and a second film with high elongation into a film composite membrane. This composite structure enables the membrane to burst at lower pressures than a single membrane could achieve, while maintaining structural integrity through the complementary properties of the two films.
Solution Approach 2:
The membrane is segmented into two distinct films with different functional properties. The first film provides structural stability with minimal elongation, while the second film provides the burst function with high elongation. This segmentation allows each film to be optimized for its specific function, achieving low burst pressure without excessive complexity.
2Stress or pressure
If a membrane with high elongation is used to achieve low burst pressure, then the degassing pressure is reduced, but the stroke movement becomes significant
Solution Approach 1:
The film composite combines a high-elongation second film (for low burst pressure) with a minimal-elongation first film (for stroke limitation). The first film acts as a constraint that limits the maximum displacement of the second film, thereby reducing stroke movement while preserving the low burst pressure characteristic.
Solution Approach 2:
Different regions of the membrane have different properties: the second film region provides high elongation for pressure relief, while the first film region provides minimal elongation for stroke control. This local differentiation of material properties allows simultaneous achievement of low burst pressure and limited stroke movement.
3Reliability
If expensive semipermeable membranes are used, then gas exchange and liquid sealing are achieved, but the cost increases
Solution Approach 1:
The membrane function is segmented into two parts: the first film handles structural integrity and connection to the main body, while the second film handles the burst function. This segmentation allows the use of less expensive materials for each component rather than requiring an expensive semipermeable membrane for the entire structure, reducing overall cost while maintaining reliability.
Solution Approach 2:
The second film with high elongation is designed as a sacrificial element that bursts at a predetermined pressure to relieve gas. This film can be made from less expensive materials since its function is temporary (bursting), while the first film provides lasting structural support. This approach reduces material costs while maintaining the required reliability for gas exchange and liquid sealing.
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 quick pressure relief at low degassing pressures with reduced installation space requirements, maintaining structural integrity and preventing foreign body ingress, while being cost-effective by using less expensive materials for the burst function.
Implementation Method 1
pressure compensation devices are known which comprise semipermeable membranes, for example, of extruded polytetrafluoroethylene (PTFE), which are gas-permeable but liquid-impermeable
Implementation Method 2
the membrane is embodied as a film composite with at least two films arranged on top of each other, wherein a first film of the films in its surface area comprises at least one cutout which is covered, in particular is gas-tightly covered, by a second film of the films
Data Source
AI summary
A degassing unit for a battery housing has a main body to be connected fluid-tightly to a rim of a housing opening of the battery housing. The main body has a gas passage opening. A membrane is connected fluid-tightly to a rim of the main body surrounding the gas passage opening. The membrane is areally stretched across the gas passage opening and closes it. The membrane bursts at a predetermined burst pressure to release the gas passage opening. The membrane is a film composite with at least a first film and a second film arranged on each other. The first film has a cutout covered by the second film so as to surround the cutout. At least one of the first and second films is connected to the rim surrounding the gas passage opening. A battery housing with such a degassing unit is provided.