THE CHAIN

How thermal runaway builds

Thermal runaway is a loop: heat starts a reaction that makes more heat, which starts the next reaction. Once it passes a certain point, the cell can't be stopped from inside.

Thermal runaway is heat feeding on itself.

TRIGGERS

What starts it

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Mechanical

Crushing or piercing, such as in a crash

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Electrical

Overcharging, external shorts or internal shorts from defects or dendrites

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Thermal

Outside heat, or a neighbouring cell on fire

Most real fires start with an internal short or abuse.

CHEMISTRY MATTERS

Some cathodes hold on to oxygen

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Charged nickel-rich layered oxides release oxygen at relatively low temperatures, which feeds the fire. LFP's phosphate frame holds its oxygen tightly, so LFP cells run much cooler when abused and rarely burn as fiercely.

This is a big reason buses and home batteries often pick LFP.

SAFETY LAYERS

What does this safety feature stop?

Protection is built in at every level: the materials, the cell, the electronics and the pack.

Several layers, so no single failure becomes a fire.

IF IT HAPPENS

Handling a battery fire

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Toxic gas Burning cells release hydrogen fluoride and other toxic gases

Re-ignition Cells can reignite hours or days later

Water Large amounts of water cool a car pack; it is the heat that must be removed

Damaged cells Swollen, hot or hissing cells should be moved away from anything flammable and handled by professionals

Prevention is far easier than putting out a battery fire.

UNIT 17 STUDY COMPLETE

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Ready for the Fab Challenge?

You've followed thermal runaway step by step and seen the layers of protection that stop it.