I can´t summon a fireball

Blah you're wrong, a fire_charge entity is the same as of a blaze whitch is SmallFireball, Fireball is from a ghast, also it fails to spawn because you don't specify direction
see: http://minecraft.gamepedia.com/Chunk_format#Entity_Format
instead use:

/summon Fireball ~ ~ ~ {direction:[0.0,0.0,0.0]}