Bought my Fiio X5 and it worked great for a few months, then one day, it got very hot ! so I sent it back for a warranty replacement, and it worked great until for just over a year, and now the replacement has done the same thing, will not power up, plugging in the charge cable, the charge light stays green, and the unit gets hot, so since it is out of warranty, I popped the back off, and checked out the battery, it isn't the battery that gets hot, but the circuits under the battery ! I won't be buying another Fiio player
 I used it 5 days a week at work, so maybe I just used it too much.
Also had the problem with both of them not connecting to my pc, plugging in the supplied cord would charge them, but I could not access the files on the memory cards.
 to Dobrescu George, I'm glad you have had good luck with the X5, that being said, I'm not impressed with the X5's I had, and am getting an Ibasso dx80
 I did email Fiio, and the response I got back was:
 

Dear user ,

Thank you for your mail and support to FiiO.

When did you buy the X5? It is X5 first gen or X5II? Are you capable to replace the battery yourself? It seems not only a battery issue only. You may take off the battery and collect the X5 to a power apply to see whether it can be turned on?

Looking forward to your feedback.
Have a nice day! 
 Best Regards,

FiiO Customer Service