How a Battery Automatically Disconnects Itself During Overheating

A safety system for battery packs that uses a heat-sensitive material to physically break the electrical connection between cells if they get too hot, preventing thermal runaway.

What it covers

This patent describes a mechanical safety device integrated into battery packs to prevent catastrophic failure. When a battery cell overheats, a heat-activatable element—such as a shape-memory alloy or bimetal—reaches a specific temperature threshold and deforms. This deformation physically forces a disconnection between the cell's terminal and the connecting part that links it to other cells. Crucially, the heat-sensitive part does not carry electricity during normal operation, meaning it only acts as a passive safety trigger. The system also includes a low-thermal-conductivity material between cells to ensure heat from one failing cell does not immediately trigger the disconnection of its neighbors.

What it doesn't cover

• —Does not cover electronic fuses or circuit breakers that rely on current-sensing logic.
• —Does not cover chemical additives or electrolytes designed to suppress fire within the cell.
• —Does not cover disconnection methods that rely on melting a conductive link (fuses) rather than mechanical deformation.
• —Does not cover systems where the heat-sensitive element itself is part of the electrical current path.

The clever bit

The system separates the safety trigger from the electrical path. Because the heat-activatable element is not part of the current-carrying circuit, it can be optimized purely for its mechanical and thermal properties without worrying about electrical resistance or power loss.

Why it matters

Thermal runaway in large battery packs, such as those in electric vehicles or grid storage, is a major safety risk. By providing a purely mechanical, non-electronic way to isolate a failing cell, this design offers a fail-safe that works even if the battery management system (BMS) software fails or the control circuitry is destroyed by the heat.

Real-world examples

• 1.High-capacity lithium-ion battery modules for electric vehicles
• 2.Large-scale stationary energy storage systems
• 3.Industrial battery packs for aerospace applications