Just yesterday we posted a video showing what can occasionally happen when a lithium ion battery receives impact damage, and today the Sydney Morning Herald has a report showing that the same thing can happen with no sledgehammers involved.

The Australian Competition and Consumer Commission said that it was investigating, but that the slimness of modern devices like the iPhone increased the risk of such incidents …

A Sydney bicycle rider […] was severely burnt when his Apple iPhone exploded after a minor fall […] Bondi management consultant Gareth Clear, 36, said his iPhone was in his back pocket and ignited after he had a fall from his bike while riding on Sunday afternoon. 

“I just saw smoke coming out of my back pocket…and then all of a sudden I felt this surging pain,” he said, adding that he felt a “searing heat” as the phone burnt through his riding shorts in a matter of seconds.

Apple has been in touch with Clear, who said that he does not blame the company for his injury but does want to raise awareness. The ACCC recommends mobile phones are not stored in pockets when people’s activities mean there is a chance of a significant physical impact.

The decreasing size and slimness of portable devices coupled with consumer expectations about battery life are a challenge for battery manufacturers. Lithium batteries are vulnerable to significant physical impact, [which] may damage the extremely thin separators that keep the elements of the battery apart.

There have been a number of previous incidents of iPhones catching fire, including one on board an aircraft.

CNET notes that the overall failure rate of lithium-ion batteries is extremely low, at around 1 in 10 million, but the sheer number of batteries in use in consumer electronics devices means that this works out to an average of 600 incidents per year. It’s likely that the vast majority of these result from impact.