EXPLAINER | The science behind a cellphone 'explosion'

A cellphone can “explode” and cause a fire rapidly, according to South African fire experts.

IGNIS forensic fire investigator MJ Steenkamp explained the issue is with lithium-ion batteries, not just cellphones.

“It seems like an explosion, but it is more a rupturing of the battery followed by rapid ignition of flammable gases caused by the thermal runaway process. It can ‘explode’ as a deflagration event when the gases are confined. Damage sustained to the battery, internally or externally, will cause thermal runaway.

“This includes puncturing damage, fall damage, basically integrity failure, overcharging, overheating and underheating. Can it cause a fire? Yes, quite quickly and it burns intensely. The bigger the battery, the bigger the initial fire or reaction from failure.”

One Sunday two siblings died in a fire at their Phoenix home, north of Durban. Initial reports from the scene in Clayfield, Phoenix were that 35-year-old Pradyumna Harisuran and his 30-year-old sister Prishni were trapped in the burning flat after a cellphone exploded on a couch.

But their mother, Sheena Harisuran, reportedly told the Phoenix Tabloid on Tuesday there was no cellphone on the couch. The cause of the fire has not yet been established.

Thermal runaway occurs when a current flowing through the cell or battery causes the temperature to rise and overheat.

Steenkamp told TimesLIVE Premium he has investigated multiple incidents involving lithium-based batteries.

“Causes have ranged from children’s toys or RC cars being heavily used or thrown about until the integrity of the battery fails, overcharging, collision causing damage to an electric vehicle, power surges affecting inverter systems, defective batteries, the list goes on.”

“Many cases include battery abuse and failure to follow manufacturer instructions. No-one reads the booklets. I know, I read them because it is part of my job. If it wasn’t for this then I wouldn’t have read them either,” he said.

Lithium-based batteries are found in almost all portable devices, including cellphones, vapes, drones, speakers, hand-held gimbals, camping fridges, power banks, cameras and on larger-scale inverters.

Steenkamp said due to the mass requirement of batteries, some manufacturers that are not entirely on par with industry standards, now produce their own batteries with major budget cuts.

“These batteries are then purchased by consumers and installed in systems or items that are constantly used because it is cheaper to replace a battery than replace an iPhone or a Samsung, and furthermore, it is cheaper to get them from a random shop selling everything from toilet paper to cellphone batteries than it is to buy the recommended battery directly from the device manufacturer.

“Now you have a less resilient battery produced with sketchy means that are now being subjugated to rigorous usage. At some point, it will fail. The ignition of the battery is quite violent, which is why it is seen as an explosion.”

“Let me ask this: how many times, if not all the time, do people put their cellphones or laptops or vapes on charge and then fall asleep knowing that when they wake up the device will be fully charged? Or how many of us plug a device in during load-shedding saying, ‘when the power comes back on, I know it will be charging’?”

Given the high energy loading of rechargeable batteries this type of short circuit results in very high temperatures. Flammable gasses are given off and the heat very quickly gets the materials that the batteries are made off to start burning, giving off the stored energy as high-temperature flames

—  Marius Atterbury, Fire Protection Association of Southern Africa CEO

Steenkamp said overcharging causes dendrite growth (development of branches), leading to a short circuit and a self-sustaining thermal reaction. This ruptures the battery, releasing flammable, toxic gases that ignite violently.

He said battery abuse isn’t just about overcharging. Defects, frequent drops, prolonged disuse before charging and failure to follow manufacturer guidelines are common causes.

“Battery failure is a real thing, and the severity of its failure is heavily understated. Unfortunately, incidents like these must occur before more emphasis is placed, and that is deeply saddening. The same concept applies to safety, where we hear, “it won’t happen to me”, until something happens, injuries are sustained, and only then do people take action.”

Marius Atterbury, CEO of the Fire Protection Association of Southern Africa, said modern battery technology is designed to store a high amount of energy in a small space.

“As with ‘normal’ electricity there will be sparks when two poles touch each other, and those electricity sparks have been the cause of many fires during mankind’s time of using electricity. In a battery this touching can happen when the barrier between the ‘two poles’ gets damaged. In the case of the notorious Samsung S7 phones that damage came from inside the battery, but external damage can also cause such a short circuit.”

“The use of a charger that is not designed for the phone, mostly to try to get the quickest possible charge rate, will possibly bring about internal battery damage due to high heat. External high heat, like leaving a phone in direct sunlight during a very hot and sunny day, may also bring about enough damage that may lead to an eventual fire or explosion.”

“Given the high energy loading of rechargeable batteries this type of short circuit results in very high temperatures. Flammable gasses are given off and the heat very quickly gets the materials that the batteries are made off to start burning, giving off the stored energy as high-temperature flames.

“Often the chemical reaction that takes place during such an event will also produce volatile gasses, which can build up and then explode. A jet flame will occur, and this can be seen during the many online video clips of cellphone and other batteries burning.”