To see starbase in the battle screen, you need to uncheck, "show fleet battles only if both sides are fleets" in the options window. Since a starbase is only one ship, they wont show up by default. You might also want to make sure you are playing with the differant battle views, since they are so big most of the time the starbase will start off camera.
Also, yes you do not need to put sensors, engins or even lifesuport on a ship if you just want it to gard your planet. Often In the early game I will make a fighter with to lasers, or such and nothing else. and crank them out for a few turns, just so all my planets are defended. But since the amout of moves a ship gets are deturmined by the speed, it is not a good practice are you get further along in the game.
