Warning signs your lithium-ion battery is about to fail (and what to do)

Most lithium-ion battery fires do not come out of nowhere. In the majority of cases the battery warns you first, and knowing what those warnings look like is one of the cheapest, most effective safety steps you can take.

The stakes are real. Fire and Rescue NSW has recorded a steady year-on-year rise in lithium-ion battery fires, and reports that people are far more likely to be injured in a battery fire than in other fire types (Fire and Rescue NSW [FRNSW], 2024). Part of the reason is the gas: research has measured large quantities of highly toxic hydrogen fluoride released during battery fires, sometimes a greater hazard than the heat itself (Larsson et al., 2017). Spotting trouble early, before a cell reaches that point, is what keeps a warning from becoming an emergency.

The warning signs to watch for

A failing lithium-ion battery usually shows one or more of these. Treat any of them as a reason to stop and act, not to wait and see.

• Heat. The battery or device is hot to the touch when it shouldn't be, including after you unplug it.
• Swelling or bulging. A phone, laptop, pack or casing that has changed shape or no longer sits flush.
• Noise. Hissing, popping, crackling or a whistling sound coming from the cell.
• Smell. A sharp chemical, solvent or oddly sweet odour is a classic sign a cell is venting.
• Smoke or vapour. Any smoke, haze or vapour, even a faint wisp, is an emergency.
• Discolouration or leaking. Scorch marks, staining, or fluid on or around the battery.
• Odd behaviour. Charging very slowly, not holding charge, or shutting down unexpectedly can point to a damaged cell.

What to do the moment you notice one

If a battery shows any of these signs, act calmly and quickly.

• Stop using and stop charging the device straight away.
• If it is safe, unplug it. Don't yank a charger from a device that is already hot or smoking.
• Move it away from anything that can burn, ideally onto a hard, non-combustible surface, outside, or into a fire-resistant containment bag.
• Don't puncture, crush, cover or submerge it, and don't put a swollen battery back into use.
• Ventilate the area if you can do so without lingering near the fumes.

Better still: prevent the warning in the first place

Most failures trace back to a handful of avoidable causes (Australian Competition and Consumer Commission [ACCC], 2023). Charge on a hard, non-combustible surface, never on a bed or sofa. Use the manufacturer's charger rather than a cheap aftermarket one. Avoid charging unattended or overnight where you can't respond. Stop using any battery that has been dropped, damaged or exposed to water. And keep spare, damaged or recalled batteries isolated, ideally in a fire-resistant containment bag, away from anything combustible (ACCC, n.d.).

Where our gear fits

If you spot a warning sign, a containment bag gives you somewhere safe to isolate a suspect battery while it cools and you arrange disposal. If a battery does ignite, a lithium-ion extinguisher and fire blanket let you respond to and contain a small fire in its early stages. And if you want your household, team or fleet to recognise these signs consistently, our short awareness courses cover exactly this.

Knowing the warning signs costs nothing and changes everything. A battery caught while it is only swelling or warm is a problem you can manage. The same battery, left another hour on charge, is a house fire. When in doubt: unplug, move it clear, and if it is smoking or hot, call 000.