I am wanting to charge my iPad in the DC port in my car. I have already got a USB car charger for my iPhone and that works fine. When I put my iPad into it it says "Not Charging." Can anyone tell me why it won't charge?
The not charging indicates that when the iPad is running, the remaining current from your adapter won't be adding much meaningful charge to the battery.
When you turn off the screen and idle the CPU, the charge rate will go up when the iPad is on, but you'll want a higher current charger or to power off the iPad if you want to maximize the current that goes to the charging circuitry as opposed to running the iPad.
You will be better off purchasing a car charger that is rated for use with the iPad. Try checking with the Apple Store.