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DIAvent®
DIAvent® – the Versatile Pressure Equalization Element for Traction Batteries
Combined Pressure Equalization and Emergency Degassing in a Single Component
The hermetically sealed housings of batteries for vehicles must be equipped with special devices that perform the necessary pressure equalization.
The DIAvent® pressure equalization element combines several functions in a single component: pressure equalization during normal operation, fast and reliable opening for emergency degassing in a worst-case scenario – the thermal runaway of a cell – and subsequent closing after pressure equalization. The element thus ensures not only significantly greater safety, but is also more robust than conventional solutions.
All of the Benefits of DIAvent® at a Glance:
- versatile functions in a single component
- small dimensions
- resealing increases safety after emergency degassing
- more robust than conventional burst vents or rupture discs made of porous PTFE film
Our Products in Detail
DIAvent® Robust, Resealable, Safe
The patented DIAvent® pressure equalization element from Freudenberg consists of a centrally arranged breathing element. The coated ePTFE is watertight and oil repellant while air can pass through for enabling bi-directional pressure equalization.
The laminated breathing element offers greater robustness compared to the PTFE films commonly used in the past. Additionally, its performance exceeds conventional solutions in the market. This means that the pressure equalization element can be correspondingly smaller.
Emergency degassing takes place via an integrated rubber valve that is arranged in a ring shape around the central breathing element. It is designed like an umbrella and opens at pressure differences of around 40 mbar between the inside of the battery and the atmosphere. The valve closes again when the differential pressure drops. This prevents large quantities of ambient air from entering the battery and causing uncontrollable reactions. It also prevents further toxic products from contaminating the environment.
DIAvent® maxFlow – Even Faster, Even More Gas Release
The DIAvent maxFlow breaks new ground in emergency venting valves for vehicle batteries. Instead of relying on an umbrella valve or rupture discs as in the past, the maxFlow uses a flat spring. This does not only enable precise adjustment of the opening pressure but also allows for a larger opening cross-section to be released, ensuring maximum airflow during emergency venting. As soon as the venting pressure subsides, the spring closes the valve again, preventing oxygen or firefighting water from entering the battery and ensuring that the battery remains sealed.
The advantages of this new valve are clear
- Adjustable opening pressure with best-in-class opening tolerances
- Immediate opening of a large venting cross-section
- Maximum venting rates
- Resealable when venting pressure drops
- Functions 100% end-of-line tested by FST
- Easy installation on the battery housing
DIAvent® HighFlow – Greater Safety With Higher Energy Density
Freudenberg has developed the DIAvent® HighFlow degassing vent specifically for battery systems with higher energy densities. The higher energy density also results in larger gas volumes that need to be dissipated quickly in case of an emergency.
DIAvent® HighFlow is primarily designed for use in batteries in larger vehicles with very high energy densities and has four times the mass flow rate of the first generation DIAvent® in case of an emergency.
To be able to achieve this in an emergency, the opening created by the rubber umbrella has not only been enlarged, but additional exhaust ducts have also been added.
DIAvent® Mini
DIAvent® Mini is the ideal pressure management solution intended for small to mid-scale batteries in electric ATVs, 2-wheeler applications, forklifts, lift trucks, power tools and many more. In comparison to the DIAvent® HighFlow the DIAvent® Mini is not meant for automotive applications. It is made up of a smaller umbrella combined with a coated ePTFE breathing element that allows DIAvent® to handle the bi-directional pressure equalization of any battery reliably, even in the harshest of operating conditions. The integrated Torx T40 mounting feature on the cover allows robust mounting on the customer application.
The Challenge: Daily and in Case of an Emergency
The Daily Challenge: Pressure Fluctuations During Operation
Air pressure changes within the battery housing of a vehicle occur during normal driving operation. For example, when the vehicle drives over a mountain pass or the temperature in the battery housing changes in the period between a cold start and high speed on the highway. These pressure fluctuations are compensated for by an air exchange of several liters of air per minute in both directions. In the past, porous PTFE foils were usually used as a pressure equalization element for this purpose. The disadvantages of these solutions are essentially the high sensitivity with regard to mechanical influences as well as contamination by particles and liquid media, which ultimately reduce the air permeability. Here, DIAvent® & DIAvent® HighFlow offers a practical alternative.
The Challenge in Case of an Emergency: Equalizing Pressure in Seconds
Foreign bodies in the cell, internal and external short circuits, defective overcharging or the destruction of the battery cell in an accident result in the release of high amounts of energy and gas volumes. The resulting gas then flows directly into the battery housing.
To reduce the resulting pressure as quickly as possible, battery housings usually have built-in rupture discs as predetermined breaking points to release the gas quickly in a controlled manner. Although these prevent the housing from being damaged, the destroyed disc leaves an opening to the outside after emergency degassing. This has significant disadvantages. Ambient air can be drawn into the battery after pressure equalization to create a combustible gas-air mixture that can cause further exothermic reactions inside the hot battery housing.
DIAvent® – the Safe and Reliable Solution
The DIAvent® & DIAvent® HighFlow pressure equalization elements are not only extremely robust against mechanical stress, but also immediately closes the rubber umbrella that is opened in the event of emergency degassing. On the one hand, environmental pollution is prevented. On the other hand, it increases safety for anyone in the immediate vicinity of the vehicle – especially during the transportation of the damaged and fire dormant battery system.
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