Fire Protection Bag for Lithium-Ion Batteries and Battery Packs

With a fire protection bag, greater internal capacity does not automatically mean greater safety. Every additional lithium-ion battery also increases the potential amount of energy contained inside the bag. In the event of a battery failure, this can substantially increase the thermal, mechanical and gaseous loads placed on the complete protection system.

Fingerhuth therefore deliberately limits the standard dimensions to 30 × 20 × 15 cm. The compact design is intended to counteract uncontrolled overloading of the bag with increasingly large quantities of high-capacity batteries.

As a practical reference, the integrated compartment system can accommodate, for example, up to six 18 V / 9 Ah lithium-ion power-tool batteries. For other battery types, the number of batteries, their dimensions and their energy content must be taken into account accordingly.

Our basic principle is therefore: do not concentrate as much battery energy as possible in one bag, but keep the capacity controlled and appropriate for the intended application.

Lithium-ion batteries do not follow a standardised form factor. Power-tool batteries differ significantly from drone batteries, camera batteries, RC battery packs or portable energy storage systems.

The Fingerhuth fire protection bag therefore features a dynamically adjustable compartment system. The individual separators can be positioned, repositioned or removed completely depending on the battery format.

This allows several smaller batteries to be positioned separately or larger battery packs to be accommodated within one continuous internal space. The system combines flexible use with a clearly defined maximum bag size.

Particularly where battery systems change regularly – for example in service vehicles, workshops, photo and film productions or professional drone operations – the variable internal layout allows the bag to be adapted quickly to the respective application.

A thermal runaway generates more than heat and flames. Significant quantities of hot reaction gases can develop within a very short period of time and substantially increase the pressure inside a closed fire protection bag.

Fingerhuth therefore uses a specially developed multilayer pressure and gas management system. The vent openings in the individual protective layers are deliberately offset from one another. This means there is no straight, open connection between the batteries inside the bag and the external vent openings.

Escaping reaction gases are redirected within the multilayer construction 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 system therefore combines two key requirements: allowing pressure relief while reducing the direct release of flames and particles through a straight discharge path.

High-temperature material alone does not make a robust fire protection bag. The closure system is particularly critical because it must keep the bag closed precisely during a thermal event.

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

Fingerhuth therefore uses solid, non-combustible stainless steel twist-lock closures. The metallic closures are high-temperature resistant and designed for high mechanical loads.

Especially in the event of strong pressure impulses inside the bag, the mechanical closure system helps maintain the structural integrity of the fire protection bag for as long as possible and prevent uncontrolled opening.

Lithium-ion batteries are not used exclusively in stationary workshops or storage areas. Tradespeople, service technicians, photographers, drone operators and model builders regularly transport their batteries between different work locations.

The fire protection bag therefore features a robust carrying handle and an adjustable shoulder strap, making the bag convenient to handle during mobile use.

The compact dimensions of 30 × 20 × 15 cm also make it easier to integrate the bag into service vehicles, workshops, transport areas and mobile workplaces.

The result is not simply a storage container, but a portable fire protection solution for users who work with different lithium-ion batteries on a daily basis.