The stock Sanyo 4.8 volt Ni-cd pack is fine. The 4.8 Ni-mh packs offered by various companies are fine also and may offer you some more time between charges. Just make sure it comes with your compatible end which is more than likely Futaba J, or you will have to solder your own on. The 4 AA Flat Packs usually work best for me, and are easy to find storage space within the Plane, but for certain things mabe the 4 AA Square Pack would be good also.