Although, incidents where a smartphone battery explodes or spontaneously bursts into flames are very rare, the consequences are among the most serious, with the unlucky user risking serious injury or even death.
With long experience in mobile phone repair, iFixit specialists have compiled a list of reasons why a smartphone’s battery might spontaneously combust in a phenomenon called “thermal runaway”.
In their investigations, iFixit specialists pierced the battery casing in various ways, experimenting with punctures from shallow to deep punctures. The tests were aimed at observing the effects on the different insulating layers of the battery, going as far as breaking the barrier between the positive and negative layers, causing an internal short circuit.
An essential detail for the severity of the incidents that occur is the charge level of the battery. Thus, a battery charged to 100% will catch fire more easily and with much greater flames than a fully discharged one. Thus, iFixit specialists have established a safe threshold of no more than 25% charge, at which small batteries, such as those used with mobile phones, are more likely to smoke if accidentally punctured or damaged by mishandling (e.g. by excessive deformation when attempting to remove them from the phone case). But for larger batteries, such as those used with laptops and tablets, it is recommended to discharge as close to 0% as possible before attempting any work on the equipment.
Another very big risk factor and not necessarily related to equipment repair is overcharging the battery. The problem can occur spontaneously, especially in the case of worn-out or defective batteries. In the case of worn-out batteries, the phenomenon may manifest itself by overheating during the charging process, with or without visible swelling of the battery. Therefore, users who notice excessive heating of the device being charged, possibly accompanied by the appearance of some chemical smell, should immediately stop the charging process and take measures to prevent a possible fire.
Unfortunately, accidents are much more difficult to prevent in devices whose batteries have hidden defects, with incidents of explosive ignition occurring randomly without obvious warning symptoms.
Finally, one last recommendation concerns the disposal of used batteries or electronics containing Li-Ion batteries. Even if they appear to be completely discharged, the risk of fire by puncture or crushing remains. Simply thrown in the rubbish bin, crushed batteries can cause spontaneous fires if they are put in a bin or loaded into a refuse collection machine. For this reason it is essential to collect spent batteries responsibly and recycle them.