That's two this month (February). The other was on an Aeroflot A320 - fortunately, on the ground. We are talking about a sort of 'C' size lithium battery that is re-charged from a laptop and then used to charge a cell-phone. I have two of them and have noted they get quite warm when charging a phone. If these errant devices had been in checked bags and the fire occurred in-flight, we would have had a catastrophic event along the lines of the Aug 19, 1980 Saudi L-10 fire where 301 people perished. I am surprised they are not on the list of banned items taken aboard aircraft.