New generation of Freudenberg DIAvent valves supports 4x faster emergency degassing of batteries

Freudenberg Sealing Technologies is introducing a new generation of DIAvent valves (earlier post), which ensure that reaction gases can escape from damaged lithium-ion batteries four times faster than before. At the same time, the valve maintains the continuous pressure compensation required for normal battery operation. The company is preparing for a rapid series launch.

If there is a mechanical defect or short circuit in an EV battery pack, individual battery cells may get very hot. Liquid electrolyte—currently used in nearly all lithium-ion cells—can then evaporate and escape into the battery housing as a hot gas. This must then be released into the environment very rapidly and in a controlled process through a pressure relief valve.

Many current battery housings feature several rupture disks for this purpose—a solution that provides rapid degassing but has some drawbacks. The bursting exposes the battery interior, which means that special precautions are required, for example when extinguishing, towing or repairing the vehicle.

At the same time, every battery housing needs controlled venting to compensate for fluctuating air pressure during normal operation. This is necessary not only when driving uphill and downhill but also because the air in the housing heats up during power input and output. If rupture disks are used for emergency venting, a separate valve may be needed to compensate the pressure during regular operation.

DIAvent offers a ventilation valve that combines regular housing venting and rapid emergency degassing in a single component. Now the supplier is presenting a new generation of this valve, which makes the emergency degassing four times faster.

Even with an overpressure of 300 millibars inside the housing, DIAvent Highflow enables a flow rate of 92 liters per second. The basic design of the valve stays the same: A centrally positioned, water-repellent non-woven element ensures effective air exchange during normal operation. If water hits the valve at high pressure, the outer layer is temporarily pressed onto a completely media-tight interior layer, preventing any water from penetrating the housing.

Emergency degassing is enabled by a ring-shaped umbrella valve surrounding the non-woven membrane. It reliably opens as soon as the pressure inside the housing exceeds the atmospheric air pressure by more than 40 millibar.

After the pressure is equalized, the reversible umbrella membrane closes again and restores the water tightness. The significantly enhanced performance of the valve, whose outside dimensions remain nearly unchanged, can be attributed to the optimized gas flow inside the component.

Engineers at Freudenberg Sealing Technologies have calculated the flow-through of the valve in detail for this purpose. Minor geometric changes, such as additional openings on the sides of the umbrella, prevent air from accumulating under the screen and enable a significantly increased flow rate.

Freudenberg Sealing Technologies is preparing a rapid series launch of the new DIAvent Highflow valve generation. The first functional prototypes are already being tested by customers, and production is already primed for expansion. This includes an end-of-line test of the valve function: unlike rupture disks, Freudenberg's valves can be tested right after production to ensure complete functionality.

Posted on 20 January 2021 in Batteries, Electric (Battery) | Permalink | Comments (0)