Safety and compliance
Thermal runaway
A self-sustaining internal heating process in which a cell generates heat faster than it can dissipate it, leading to venting, fire or propagation to adjacent cells.
What it changes in practice
Thermal runaway is triggered by internal short, overcharge, mechanical damage or external heat, and once started it cannot be stopped by cutting the current. The design response is layered: prevent the triggers with a correctly configured BMS, prevent propagation with thermal barriers or spacing between cells, and manage the consequences with venting paths and enclosure design. Chemistry choice matters here, which is part of why LFP is preferred for stationary storage.
Why it matters when you specify a cell
Design for propagation, not only for onset. Chemistry sets the onset temperature and the energy released; spacing, barriers and fusing decide whether one cell takes its neighbours with it. In a multi-cell pack, the mechanical layout is a safety feature, and it is much cheaper to design in than to retrofit.
Related terms
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Other terms in this group
Transport, safety and what the documents actually cover.
UN38.3
The transport test regime lithium cells and batteries must pass before they can be moved by air or sea, covering eight tests including altitude, thermal, vibration, shock and external short circuit.
Read the entry →IEC 62133
The international safety standard for sealed portable secondary lithium cells and batteries, with part 2 covering lithium systems.
Read the entry →IEC 62619
The international safety standard for secondary lithium cells and batteries used in industrial applications, including stationary energy storage.
Read the entry →UL 1642
The North American standard covering lithium cells, with UL 2054 covering battery packs assembled from them.
Read the entry →MSDS / SDS
The safety data sheet describing the chemical hazards of a cell, its handling requirements and the response to fire, leak or exposure.
Read the entry →