How Ventseal-Light Works

Taking the Pressure Off Car Batteries

In the world of automotive innovations, the move toward greater fuel efficiency and thus a smaller environmental impact has led to the widespread use of stop-start technology. Thanks to Trelleborg Sealing Solutions, a small but ingenious valve seal is meeting the considerable demands placed on car batteries by such systems.


  1. Pressure build-up is a problem in the car batteries used for stop-start systems
  2. Ventseal-Light from Trelleborg Sealing Solutions combines a venting and sealing function to overcome this problem
  3. Demand for the seal is rising along with the number of applications for this type of battery


on excessive fuel consumption nowadays, stop-start systems have become an attractive option for car manufacturers, since this technology can lower consumption by between two to ten percent. Europe was an enthusiastic adopter and now both the USA and China are increasingly implementing these systems in their new vehicles, too.

Stop-Start Technology

However, stop-start vehicle technology puts a lot of strain on the car’s battery, because during those periods when the engine is automatically switched off the battery is the sole source of power for all the on-board electrical devices, such as air conditioning or heating, entertainment and navigation systems. In addition, advanced stop-start systems that incorporate regenerative braking or passive boost add to the stress placed on the battery.

The automotive industry uses a type of lead acid battery in its stop-start systems called an absorbent glass mat (AGM) battery. This refers to the fiberglass mat that absorbs and retains the sulfuric acid while also separating the positive and negative plates. This battery type has many advantages, including long life, vibration resistance and, since it is completely sealed, it is virtually spill-proof and maintenance-free, as well as being recyclable.

Pressure Must be Released

Crucial to the correct operation of AGM batteries is the ability to release pressure from the minor gassing that occurs during rapid charging and which could lead to a drop in battery performance and potentially explosive fumes. To deal effectively with this issue, Trelleborg Sealing Solutions has developed the Ventseal-Light, a patented design that combines a seal and a pressure-relief valve in one product.

The valve opens at low pressure for safety reasons and closes automatically to prevent leakage from the battery. This allows for a high rate of charge and discharge, which occurs when the engine switches on and off. Although it is only a tiny component, this critical part needs to provide reliable sealing over the entire life of the battery and to operate at extreme temperatures. The Ventseal was developed by Trelleborg Sealing Solutions in Stuttgart and originally launched on the market in 2001. In 2012 production was switched to the company’s Maltese site and since then more than five million euros have been invested in meeting the rising demand for the Ventseal-Light.

Rising Demand

Martin Hignett, Managing Director of Trelleborg Sealing Solutions in Malta, praises the collaboration with the Stuttgart office, which manages the Ventseal project.

Production is currently set for 160 million Ventseal parts annually, yet he foresees this number rising in line with the increased demand for AGM batteries. The batteries have considerable potential for use in other types of demanding applications, ranging from storing the energy collected from solar panels and wind turbines, via jet skis, boats and mobility vehicles, right up to implementations in aircraft.

How Ventseal-Light Works

Ventseal-Light is a patented, low-pressure valve combining excellent impermeability with a secure opening and closing behavior. It is suitable for all cases where the pressure in a closed receptacle must be kept below a certain limit, while at the same time any ingress from the outside has to be sealed off securely. Opening pressures for the valve range from 50 to 400 mbar and it is available in two different types of elastomer material, depending on the pressure requirements and media used. In terms of function and cost, Ventseal-Light is an optimized version of the wellknown Ventseal series.