Make sure you have no background running apps that are fetching data in the background from the Internet.
Also, an iPad will charge faster with WiFi turned OFF when the iPad is not in use.
Tap on the link below to my iDevice/iOS performance/optimisation user tips link.
https://discussions.apple.com/docs/DOC-10344
Try all of these tips and leave each tip active together.
DO NOT simply try every tip individually, expecting just one tip to be a performance “cure all”.
Many of these tips are designed to work together to help improve overall iOS/iDevice performance and battery life.
Good Luck!