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Mobile network operator EE has temporarily suspended its power bar swappable charger scheme and recalled a batch of units after receiving reports of overheating and exploding devices.
Medical student Katy Emslie said on Twitter that her charger exploded during a charging cycle, starting a fire that caused severe burns to her hand.
EE said it had identified a very small number of incidents where power bars had overheated and posed a fire safety risk.
The power bar scheme was launched in April 2015, in an attempt to help users struggling with the perennial problem of smartphone batteries running low during the course of an average day.
The scheme provided EE customers a free power bar, obtainable at any shop, by requesting a one-time SMS code. The 2,600 milliampere hour (mAh) units contain sufficient capacity to charge a smartphone to full battery and have a guaranteed lifetime of 500 charges.
EE customers can either retain and recharge the unit themselves or return it to an EE retail store for a fully-charged replacement. The scheme is also open to customers of other networks for a fee. Until recently, it had been relatively successful, with more than a million consumers requesting power bar units.
Customers with potentially faulty power bars can identify them by a code found on the side of the device, which reads E1-06.
EE said customers should stop using these units immediately, unplug them from the mains supply, and return them to their nearest EE store.
“Customers returning batch E1-06 will be issues with a replacement once our investigations are complete,” said EE.
The operator insisted it had not seen any problems with other batches, which met all legal safety standards.
Generally accepted guidelines say that users of portable power banks should avoid leaving them plugged in for prolonged periods of time, refrain from charging them overnight and ensure they are charged in a well-ventilated environment. Power banks naturally become warm during charge and discharge cycles, but their use should be discontinued if they become hot to the touch.