If your opponent is smart and you go in with a bunch of battle cruisers, they will storm or plague and kill all your hard work. So...before sending the BC's in, go and use your science vessel to EMP. It makes the units ENERGY and shield go to zero and they'll hafta wait for it to recharge before they can storm of plague. If they are protoss, then just EMP some more buildings and then they will be basically cut in half. If you upgrade the BC damage then, you shud have an EZ time killing all units stuff in under 10 hits. Be sure to use at least 10 BC.

CreepColony's Opinion: You can also EMP them while you are attacking.