The Bat Armor was an exosuit built by Batman to compensate for his physical limitations as he got older. Unfortunately, the suit gave him heart problems so he was unable to use it for very long. The suit was capable of sliding its parts under each other so it could be worn in a smaller state before being activated and returned to full size.
History
After finally convincing Bruce to show him around the Batcave, Terry McGinnis asked him about the armor. Bruce told him it was intended to make up for his old age, but caused him heart problems that prevented him from using. Terry expressed his disbelief that Bruce would let a heart problem stop him. Later on, Terry was kidnapped by the recently escaped criminal, Inque, who had been in the cave and knew Terry had an "old man" helping him. Inque used the communicator in Terry's cowl to tell Bruce she would kill him if he didn't give himself up. Bruce arrived covered in a coat and wearing a scarf and sunglasses to cover his face. After Inque attacked him, Bruce activated the Armor and its parts slid into place around him, allowing him to fight as Batman once more. the fight allowed Terry to break free and use a Batarang to break the skylight and let the rain wash Inque away.