iPhone 5S not charging after being dropped

Ok maybe a bit of a strange one.

I dropped my iPhone 5S and the screen came off and various ribbon cables broke, including the one for the TouchID sensor. When I was looking at it to see what replacement parts to buy on eBay, the palm of my hand touched the Touch ID cable and that particular cable started to smoke slightly.

I purchased a screen assembly, connected it all up, put phone on charge and screen shows the empty battery symbol so I leave it for 30 mins to get its initial charge.

It's now been on charge for approx 2.5 hours and it is still showing the empty battery symbol. When I take the phone off charge, it shows the empty battery symbol with a lightning connector.

My first thought was that the battery was screwed, but the phone wouldn't show the empty battery symbol with a lightning connector when it's not plugged in.

It also can't be the lightning port as it recognizes when it's plugged in.

Does anyone have any suggestions as to what might be the problem?

Further to the post above, I forced the iPhone into DFU mode, connected it to iTunes, iTunes downloaded a software update, installed the software update (I could see the software loading on the iPhone screen), but now that's completed the phone has gone back to just showing the empty battery symbol.