Why won't my Galaxy Tab 2 10.1 charge?

A

AC Question

My 3 year old Galaxy Tab 2 10.1 that won' charge

Suddenly I have a problem charging my Tab2. I haven't had any problems before. If I plug it into a plug socket it immediately turns off the tablet and doesn't charge. If I plug it into the pc it stays on but has a red cross in the charging symbol at the top right. I have tried (without success):
- blowing into the socket
- holding the start button down, and also the start and volume button down for 30 seconds
- turned off wifi (although it has always charged fine before with it on)
- tried unclipping the battery connection and replacing it
N)OTHING works
Also, with wifi on I now cannot connect to the internet with google.
I now have little charge left in the battery and have no idea what to do.
How would I know if the battery needed replacing?