One of the most dangerous misconceptions about EV battery fires is that they happen without warning. In reality, a battery undergoing the early stages of failure almost always produces signals — physical, auditory, and olfactory — that something is wrong. Recognising these signs and acting quickly can be the difference between a near-miss and a catastrophe.

1. Battery Swelling or Deformation

A healthy lithium-ion battery maintains its shape. If your battery pack, e-bike battery, or lithium-ion cell appears to have changed shape — puffed up, bowed, or deformed — this is a serious warning sign. Swelling indicates internal gas production caused by electrolyte decomposition. The battery chemistry is already compromised.

What to do: Stop using the battery immediately. Do not charge it. Place it in a lithium-ion containment bag in a cool, ventilated outdoor location, and arrange safe disposal with a certified recycler. Do not place it in household waste.

2. Unusual Heat During or After Charging

Some warmth during charging is normal. Significant or uneven heat — especially if the battery or charger is uncomfortable to touch, or if heat is concentrated in one area — is not. Localised heat often indicates a failing cell working harder than its neighbours.

What to do: Disconnect the charger. Allow the battery to cool in a ventilated space. If the heat was extreme, have it inspected by a qualified technician before charging again — or store it in a containment bag while you arrange disposal.

3. Chemical or Burning Smell

Lithium-ion batteries undergoing internal breakdown produce distinctive chemical odours — often described as sweet, acrid, or similar to burning plastic or nail polish remover. If you notice an unusual smell coming from your battery, charger, or charging area, treat it as an emergency.

What to do: Evacuate the area. Do not investigate the source. Call 000 if the smell is strong or accompanied by other warning signs. Open windows and doors if safe to do so without entering the affected area.

4. Hissing, Crackling, or Popping Sounds

Sounds emanating from a battery are almost always bad news. Hissing indicates gas release under pressure. Crackling or popping can indicate internal short circuits or rapid cell decomposition. These sounds are often the last warning before visible fire.

What to do: Evacuate immediately. Call 000. If you have an EV fire blanket and can deploy it safely from a distance without approaching the battery, do so — otherwise leave it entirely to emergency services.

5. Sudden Loss of Capacity or Erratic Behaviour

A battery that has lost significant capacity unexpectedly, charges and discharges erratically, or causes your device to shut down unexpectedly may have internally shorted cells. This is particularly relevant for e-bike batteries that may have been involved in a fall or water ingress — internal damage is not always immediately apparent.

What to do: Have the battery professionally inspected before continued use. If you suspect physical damage or water ingress, err on the side of caution and replace the battery rather than risk a fire. Store it in a fireproof containment bag in the interim.

A Final Word on Prevention

The best fire safety strategy prevents a fire from starting. Use manufacturer-specified chargers. Never charge unattended overnight. Inspect batteries regularly for physical changes. Store batteries in cool, ventilated locations away from exits. And ensure the right equipment is within reach for when prevention is not enough.