Exit out of the room and return to the Containment room. If it attacks a second time, you should still be able to survive. On the way back, if you angered it before, you'll run into the same monster near the exit. Grab the battery pack and head towards the exit. If it attacks, it will move to the other side of the room afterwards.
Don't worry if you fail, you should be able to withstand an attack from the creature. It can be difficult to get the battery pack from the yellow compartment on the wall without getting attacked by the monster, but throwing an object at it and running away and hiding before it sees you works. As you get closer, it will begin transforming into a much larger monster until it turns around and attacks. A monster will be standing in this area right next to the battery pack. Next, go through the door on the right to the Power Room.
