What you really need to do is read some of the inputs from other people here on RCU. There are many other postings asking questions and offering advice about all sorts of battery issues.

One thing you really want to make sure about when you buy a battery is that you are getting a quality product that you can rely on. The last thing you want is to find out that a cheap battery that you just put in your bright and shiny new aircraft is a junk battery that either won't hold a charge or has breaks the tabs that connect the cells due to some inherent vibration. That's a tough way to learn about junk batteries because you end up picking the battery out of a pile of broken balsa, shredded covering, and splntered ply.

Things you should be looking for is how the batteries are bonded betewen each other, size of the wire used, strain relief for the wires, how the battery packs are bound together in a pack, capacity, discharge rate, and so on.

Don't be afraid to spend a little more for a decent quality battery.

RadicalRC and NoBS batteries are probably as good a place to start, but not the only place to buy batteries. I can tell you this, though. I bought a LiPo from RadicalRC a short while ago. I think I accidentally shorted the leads together when soldering on the Deans Connector. Sloppy and I should have known better, but that's besides the point. Anyway, the gentleman at RadicalRC replaced that battery, no questions asked. So, another great feature of a battery supplier is service and that they back up what they sell, no matter what. I'm sure if I crashed the plane and the battery was squished then they would balk at replacing the battery, but that's not their fault.

Just find a decent supplier that has a good quality battery and backs it up, and go for it.