Exclusive EE management was warned that its popular "Power Bar" phone charging devices had serious safety risks before they were given to customers, the Register has learned. A Power Bar subsequently exploded, injuring a young woman badly enough that she required hospital treatment, and some Power Bars have since been recalled.

Last month, 26-year-old medical student Katy Emslie suffered burns to her hands and spent five hours in A&E and had plastic/reconstructive treatment after her Power Bar, which was charging from her laptop, exploded in the middle of the night while she slept.

Ty @EE for the powerbar which exploded, almost burned down our house+left my hand like this: #Firework pic.twitter.com/MRzdsbj52P — Katy Emslie (@kemslie89) July 24, 2015

Internal EE documents seen by The Register make it clear that serious safety concerns regarding the Power Bar had been raised at the company before the device was launched: but it was launched anyway.

EE, Britain's largest mobile operator, promised "never-ending power" for its millions of customers by offering them free Power Bars, which they can collect from the company's retail outlets - and later return them to be recharged, swapping for a freshly-charged Bar. Early in the project EE carried out a risk review through its own safety and sustainability team. It claimed risks had been assessed and that the product met legal requirements including European battery regulations. But it is unclear how detailed that exercise was.

Specific concerns raised within EE in the documents seen by the Register included variable quality in the cells used in manufacture, a risk that the Power Bar could easily be overloaded and catch fire if used with a faulty cable, lack of measures to ensure that Power Bars circulating among EE's users and shops would remain within their safe lifespan, a risk that bars being charged en masse in shops might suffer "thermal runaway" and burn down buildings, and other dangers.

Unfortunately, given the alleged risks to the user, the Power Bar has been a big hit among customers, with EE having to regularly expand its stocks. Even given the existing concerns over safety, El Reg understands that no product improvements were made to later batches of the device.

On Wednesday lunchtime, EE recalled thousands of Power Bar devices and said that the only chargers that posed a potential fire risk came from one faulty batch – models labelled "E1-06".

There are currently 1.5 million Power Bar chargers in circulation in the UK.

The Register sought comment from EE. The firm's spokesbeings said:

“We strongly refute any suggestion that safety concerns were ignored or dismissed without careful consideration. The product was subject to a rigorous testing process by our safety and products teams and all EE Power Bars meet EC electrical safety standards.”

When asked about the Emslie case and whether any compensation had been offered to her following the incident, the EE spokesman said: "We will discuss with customers on an individual basis."

Emslie did not respond to a request for comment from El Reg. She did, however, tweet a link to EE's official recall notice after we contacted her. ®

Bootnote: On 16 December 2015 EE expanded its recall to all EE Power Bars.