The iPad 2 has the same dock-connector port and power requirements as the original iPad, which means that if you have a charger or battery pack made for the original iPad, it should work just fine with the new model.
However, if your current charger or battery wasn't made for the iPad, the answer is a bit more complicated. As we , the iPad requires more juice than any iPhone or iPod, so power accessories made for those devices--in other words, those that don't sport the badge--won't charge the iPad as quickly as its own 10-Watt USB charger. High-power iPhone chargers, such as Apple's iPhone Power Adapter and some AC and auto chargers designed specifically for the iPhone, will charge the iPad more slowly, even while the iPad is in use. Other iPhone chargers and most chargers designed for iPods don't provide enough juice to charge the iPad's battery during use; you'll see the message in the iPad's menu bar. (These lower-power accessories will the iPad during use; they just can't charge the battery at the same time. When you put the iPad to sleep, the iPad's battery will charge, but very slowly.)
The situation is similar for external batteries. Most batteries made for the iPhone or iPod will charge your iPad's battery only during sleep, and even then, very slowly. A few higher-power iPod and iPhone batteries will be able to power the iPad during use, but won't charge its battery unless it's asleep.
Bottom line: If you want to be able to charge your iPad's battery quickly, you'll want a Made for iPad battery.