High-voltage batteries in electric vehicles require reliable protection against water, dust and pressure fluctuations. A number of years ago MANN+HUMMEL developed reliable venting units for this purpose. Now the VentPlus modular kit offers the right solution for each electric drive.
Powerful high-voltage batteries are the core of electric mobility. Therefore, the ingress of water and dust into the battery system has to be prevented, while at the same time pressure compensation has to be enabled. Larger pressure fluctuations can seriously impact the tightness of the battery housing and therefore also have a negative effect on the function of the battery or even completely destroy the battery. Fluctuating pressure may, for example, occur due to changed ambient temperatures or height differences and in some circumstances lead to plastic deformation or in the worst case to a damage of the battery housing parts. But there is also a risk from the inside of the battery: in case of cell failure or mechanical damage it can result in the degassing of battery cells leading to excess pressure in the housing. This over pressure has to be safely removed in order to prevent a bursting of the housing. Accordingly, MANN+HUMMEL began the development of venting units in 2011 and has produced these repeatedly in series since 2013. MANN+HUMMEL venting units, for example, are fitted to all electric and hybrid vehicles produced by the BMW Group. Many further projects are currently in preparation and will enter series production shortly.
The VentPlus modular kit from MANN+HUMMEL perfectly combines flexibility and the advantages of standard solutions such as quick availability. Customers can choose the right component for their requirements from a number of versions with well-proven components.
The result is a customized venting unit for their individual application.
The membrane is a key component of the venting unit. On the one hand it has to enable the gas exchange of the battery housing and on the other hand has to reliably prevent the ingress of particles and liquids. The fluorinated membrane impedes the adhesion of particles and liquids which could lead to a blockage. The long-term durable, semi-permeable PTFE membranes used by MANN+HUMMEL protect the battery against dust and ambient water and also against water from water-jet or high pressure steam cleaning devices. At the same time the membrane serves as a venting unit against excessive pressure inside the system. If the over pressure there increases to a defined level, this leads to a cracking of the membrane and therefore to a large cross-section for an effective emergency degassing. The VentPlus modular system offers customers the choice between two membranes with different permeability and bursting pressures.
A protective grid on the venting unit prevents access to the high-voltage components inside the battery even if there is a fire. Depending on the required protection class, customers can choose between a honeycomb design and a slot design. In addition, the complete venting unit is designed to be flame-retardant. The VentPlus modular system offers three types of seals with different material specifications in order to meet the respective chemical resistance requirements. The black EPDM seal is chemically resistant to coolant, water and air. The red VMQ seal offers additional limited resistance to oil and fuel. The blue FKM seal withstands all the named media and is also designed to be flame-retardant.
VentPlus offers flexibility for the application regarding the way the venting unit is mounted to the battery. Depending on the version, the component can be fixed using a metric screw connection or by screwing directly to the battery housing. In addition, the internal screw on the inside of the housing prevents misuse by unauthorized persons. Using the special geometry of the housing, a leak test for the whole battery system can be made via the venting unit.
The importance of the venting unit for the function and reliability of the electric drive is essential. This is why all elements of the VentPlus modular system are subject to a strict inspection process with a 100 percent test of the main function parameters. MANN+HUMMEL is currently working on further solutions for high performance venting units. With extended functions, they will be able to perfectly meet future requirements for efficient and reliable battery venting systems.