I just ordered on of these engines. I plan to put it in a P- 40 that I previously had a K&B 40 in. It weighs about twice the K&B but then I had to put in several ounces of lead to balance it before.
The receiver used two 1100ma A123 cells. I will just tap off of that with a couple of diodes for the ignition so I wont need another battery.
Several people have shown that you can use the same battery for the receiver and the ignition if you are using 2.4GHZ