Given the random exploding or catching of fire of power banks on flights, airlines have either banned or restricted the carrying of power banks to hand luggage only.
I read a dozen or more random articles around this. Almost all of them ranged the causative factors from poor quality battery packs, to pressurized cabins on aircraft, to the possibility of the power bank getting dropped, damaged or crushed by luggage contents or by any heavy weight placed over them, as possible reasons.
However, I could not find one possibility on any of those articles.
Could users be plugging the power bank’s cord back into itself for convenience when traveling?
Based on the little reading I did on the matter, power banks have an operating range of around 3.7-4.2 Volts.
However, mobile phones need 5V to be charged. So when you plug your power bank to charge your phone, the power bank’s circuitry boosts that 3.7 odd Volts to 5V, also causing an energy-loss of 10-15%.
In theory, this also means that if you connected both ends of the cord to the power bank, while it would charge and discharge itself, due to the energy loss, it would discharge itself soon.
However, until that happens, I would assume that the 5V output voltage going back in the lower volt input, could cause its temperature to increase? Ever plugged a 120V product into a 240V outlet and seen smoke come out of the adapter?
Could that be a cause of the instances when power banks catch fire on flights? Perhaps in a work or home environment, users might not be as particular about the free end of the power cord as much as when they travel and would like the cord to still be with the power bank, wherever the their luggage the power bank might end up being shuffled around to.
Because if that is the case, it might simplify airline restrictions and checking to some extent, and the airline (and public service messages) could simply ask people not to plug both ends of the cord into the power bank when it is not in use.