Charging your iPad 2
Image from: www.droiddog.com
It was brought to my attention that the iPad does not charge very well when it is plugged into a computer's USB port. This problem is worse on most PCs and in many instances the iPad will not charge using a PC, but will on a Mac. However, the rate at which it will charge is much lower using any computer over the wall outlet. This is because most USB ports only support about 1/2 amp for charging, where the wall allows for up to 2 amps.
So my recommendation is to charge your iPad overnight using the wall adapter once the charge is below 30%. This way by morning your iPad will be charged to 100% for the next day. Remember the battery can last 10 hours of regular use or up to 3 days with sporadic use.