If you are using 2.5 rx, a 4.8 will not provide enough power and could cause your rx to shut down in flight, (known as brown out). the 2.4 rx will reset itself but by the time it does, plane is usually on the ground. If you are flying 2.4 you need at least six volts for the Rx pack. Irun at least 5 cell, six volt packs.