I have been using Turnigy Blue 2.2 amp 20C and they are inexpensive and are a perfect fit. You can find them at Hobby King for around 12 dollars apiece and they do an adequate job. I like them because I have other platforms [RC Planes] that I use them for. There are other more expensive batteries out there for sure but these will get the job done. Make sure you invest in a decent smart lipo charger so you can charge multiple batteries. This will save you tons of time so you can enjoy your hobby more.