I used 2 batteries but was burning up ignition modules with the 7.2 v A123 batteries. Started using the RcXel IBEC and have had zero problems. But I only switched over a couple of months ago.
Syssa Aircraft has one that reduces the voltage to the ignition down to 5.1v. The voltage to the receiver is not affected. I use 2300 mah A123 batteries. The IBEC eliminates several points of potential failure, the weight and expense of a separate battery pack, and the hassle of maintaining and charging 2 batteries.