Why does my tablet show a red x in symbol of it battery? Itried to plug in to wall and it does it also. Is it charging when plugged into wall plug with red x in battery symbol.i haave been powering down to charge
I have a similar problem with the Galaxy Tab 1. It means the charger is faulty and won't charge the tablet (or will charge it very slowly - which seems to be your case). Try squiggling it around a little bit until it charge, also consider buying a new Samsung tablet charger (the phone charger has a lower output, which is inadequate for a tablet), don't use the knock-off brands!.
If the red X is there even when it's not charging, then the battery is faulty, take it to the service center.
The problem is that your tablet needs to recognize your charger as a charger that can provide 2A. But only a Samsung charger will provide the right signal. Any other USB power source will limited to 0.5A. The result is that you need to get an original charger from Samsung.
See more explanation in my answer at How much power does a Galaxy Tab 10.1 charger need to supply?.