Battery replacement

Go to this web site for information about how to request battery service for your iPad: iPad Repair & Service - Apple Support

For cost and availability, enter your model information in the "Get an estimate" box at the bottom.

Is it really time to change your battery? See this excerpt from: Batteries - Maximizing Performance - Apple

"A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge."

Applicable Battery service replacement costs for your country/region can be established here:

iPad Repair & Service - Apple Support

For eligible devices, Apple generally operates a rapid-exchange service for qualifying devices, where your own iPad is exchanged for a renewed/reconditioned iPad of the same model and specification - this being in lieu of replacing the battery within your own iPad. The exchange cost is exactly the same.

The Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) can arrange battery service:

Genius Bar Reservation and Apple Support Options - Apple