The Three Safety Keys in Prismatic Aluminum Battery Case: OSD, Fuse, and Explosion-Proof Valve

With the rapid development of new energy vehicles and energy storage systems, battery safety has become a core concern in the industry. Especially for prismatic cells in the Automotive Battery Aluminum Case and Aluminum Case for New Energy Cars structures, ensuring battery safety under extreme conditions such as overcharge, short circuit, and thermal runaway has become a key issue in power battery design.

 

The OSD flip-up plate, fuse structure, and explosion-proof valve (vent) located on the battery cover form the triple safety protection system of the prismatic Lithium Battery Aluminum Case, known in the industry as the "Three Safety Keys." These designs not only safeguard stable battery operation but also establish the dominant position of battery aluminum cases in new energy battery structures.

 

 

 

 

 

In new energy aluminum battery cases, the OSD (Overcharge Safety Device) is the first-response active safety device. The OSD is a metal flip-up plate located beneath the negative terminal of the battery, normally insulated. When the battery's internal pressure rises to approximately 0.4-0.5 MPa due to overcharging, the OSD rapidly flips and contacts the negative conductive block, creating a temporary short circuit.

 

This mechanical action triggers the current cutoff system, allowing the battery to terminate charging and prevent thermal runaway. The OSD typically works in conjunction with a fuse structure, providing a dual safety mechanism of mechanical triggering and electrical disconnection. This multi-layered protection approach has become a standard safety strategy in aluminum battery casings and power battery case designs.

 

 

If the OSD is a mechanical trigger, then the fuse is the circuit's "ultimate brake." The fuse is typically integrated into the positive terminal connector and features a precisely controlled, narrow neck design. When the OSD triggers, creating a short circuit, the instantaneous current can reach thousands of amperes. The fuse then melts within milliseconds, completely shutting off the current path.

 

This "self-destruct" design ensures the safety of the battery shell: it remains unaffected under normal operating current, but instantly melts at abnormally high currents, preventing thermal runaway at the root. The fuse's characteristics require rigorous calculation and experimental verification to ensure rapid response and long-term reliability across all Prismatic Cell Aluminum Battery Case configurations.
 

 

When an internal battery short circuit or thermal runaway causes gas pressure to soar to 0.9-1.0 MPa, the explosion-proof valve (vent) becomes the last line of defense. Typically located in the center of the top cover, it is constructed from a scored aluminum sheet or multi-layer composite film. It ruptures precisely along a pre-defined weak line, releasing high-temperature gases and preventing the shell from bursting.

 

Although a passive safety component, the explosion-proof valve, in extreme circumstances, determines whether the EV Car Battery Shell and Rechargeable Aluminum Shell can avoid catastrophic rupture. Its design must balance pressure release speed, rupture accuracy, and corrosion resistance, making it a critical safety node in lithium-ion battery aluminum shell engineering.

 

 

 

 

The three major safety components of the Lithium Batteries Square Aluminum Shell form a progressive defense system:

 

Scenario Type	Trigger Condition	Activation Component	Core Protection Function
Overcharge Protection	Internal air pressure reaches 0.4–0.5 MPa	The OSD	mechanically flips, creating a short circuit
Current Cutoff	When the OSD is triggered, a high current is instantly generated	The fuse blows	severing the main circuit
Extreme Pressure Relief	Air pressure rises to 0.9–1.0 MPa	The explosion-proof valve	precisely ruptures to release pressure and prevent explosions

 

This design concept enables the New Energy Vehicle Aluminum Battery Case to automatically activate corresponding protections at different risk levels, building a "defense in depth" system and significantly enhancing battery safety redundancy.

 

 

The high-performance Power Battery Cover Plate and Deep Drawn Aluminum Battery Housing are not isolated designs, but are closely integrated with the battery cell manufacturing process. A complete prismatic aluminum battery case (i.e., a prismatic cell aluminum battery case) typically goes through the following key stages:

 

Process	Key Content	Control Points
Electrode Sheet Fabrication Coating	Laminating, Tab Cutting	Coating Thickness and Consistency
Cell Assembly Winding/Lamination	Welding and Case Insertion	Tab Weld Strength and Sealing
Filing and Activation Filing	Sealing and Formation Electrolyte	Quantity and SEI Film Quality
Capacity Separation Testing	Capacity Separation and Traceability	Electrical Performance Consistency and Traceability

 

During the assembly stage, bare cells are encapsulated in a Battery Pack with an Aluminum Housing or a Pack with an Aluminum Housing. Welding accuracy determines the sealing effectiveness of the Power Battery Case, while the thermal conductivity of the aluminum case directly impacts thermal management performance. Some systems also incorporate a LiFePO4 Soft Pack Cell module to enhance safety, stability, and cycle life.

 

 

The popularity of prismatic aluminum battery cases stems from their balance between energy density, heat dissipation, and safety structure. The industry is currently exploring more intelligent safety designs, such as integrating temperature-sensitive explosion-proof valves into power battery shells, placing PTC thermistors on the positive electrode, and even developing smart covers that can monitor air pressure and temperature in real time.

 

With the deepening application of CTP (Cell to Pack) and CTC (Cell to Chassis) technologies, the structure of the battery pack with aluminum housing is evolving towards integration, placing higher demands on safety structural design. Future new energy vehicle aluminum battery cases will no longer be simply mechanical protective components, but intelligent enclosures integrating electrical monitoring, temperature control feedback, and pressure relief functions.

 

 

 

 

From the mechanical flipping of the OSD to the current-cutting fuse, to the precise pressure relief of the explosion-proof valve, these three devices together form the safety defense line for prismatic aluminum-cased batteries. Their coordinated operation not only ensures the stable operation of the battery cells but also establishes the technological status of lithium battery aluminum cases and battery aluminum cases in the new energy industry.

 

When you see the sturdy aluminum case for new energy cars in the power system of new energy vehicles, or the rechargeable aluminum shell of portable energy storage devices, please remember: it is these seemingly tiny safety designs that allow modern energy systems to find a perfect balance between high power, high density, and high safety.