changing battery on ipad2

In the USA, Apple will replace the battery for $99 (see http://www.apple.com/batteries/replacements.html).

Whether you want to spend the money for that or an entirely new iPad is only something you can decide.

I would try a few things before replacing the battery...

1. Try a different cable and/or charger.
2. Try cleaning the iPad's connector port.

Post back if these don't work.