Fire Protection & Charging Bag for E-Bike Batteries up to 750 Wh

A thermal runaway generates more than heat. Large quantities of hot reaction gases can develop within a very short time, significantly increasing the internal pressure of a closed fire protection bag. A technically effective design must account for this gas generation without simultaneously creating a direct escape path for flames and hot particles.

For precisely this purpose, Fingerhuth developed a special multilayer pressure and gas management system. The vent openings in the individual protective layers are deliberately offset from one another. As a result, there is no straight, open connection between the battery inside the bag and the external vent openings.

Hot reaction gases are redirected within the multilayer system before reaching the external openings. At the same time, the intermediate layers provide an additional barrier against directed flame jets, high-velocity gas streams and hot or burning battery particles.

The concept therefore combines two fundamentally opposing requirements: allowing pressure relief while reducing the direct release of flames and particles.

The performance of a fire protection bag is not determined solely by its high-temperature fabric. A critical weak point can be the closure system. The bag must remain closed and mechanically stable precisely during the thermal event.

Textile straps, plastic buckles, hook-and-loop fasteners or conventional zippers can lose their mechanical properties, melt or contribute to flame spread under intense thermal exposure.

Fingerhuth therefore uses solid stainless steel twist-lock closures as a non-combustible closure system. The closures are high-temperature resistant and designed for high mechanical loads.

This is particularly important in the event of pressure impulses inside the bag. The closure system helps maintain the structural integrity of the bag and prevent uncontrolled opening during the battery event.

The E-bike version was specifically developed not only for storage, but also as a fire protection and charging bag. An integrated protected cable feed-through allows the charging cable to be routed into the protected interior of the bag.

The E-bike battery can therefore remain completely inside the closed bag throughout the charging process. This operating condition is particularly relevant because cell failures or technical defects can also result in a thermal event during charging.

The protection concept consisting of a multilayer high-temperature construction, pressure and gas management and a mechanically robust stainless steel closure system remains fully effective during charging.

The bag was developed for E-bike batteries up to 750 Wh and has been tested multiple times under real battery conditions.