Original post by: Minho ,
If the battery is getting hot, it's likely because there is a large current drain occurring (something on your phone is drawing excessive current). Let your device cool off and then start by disconnecting the screen assembly ([https://www.ifixit.com/Guide/iPhone+5s+Display+Assembly+Replacement/309623|follow this guide]) and then connecting your phone to an iTunes enabled computer, preferably with a genuine Lightning cable. Leave it in that condition for 30 minutes to see if the battery still gets hot. If not, then add the screen (LCD & Digitizer) and then the front camera & sensor flex until you isolate the issue. Repair or replace as necessary (or get back to us with more details...make sur update your question or comment on a specific answer so we get notified).