The Dry Cell Battery is an item found inside Room M6 on the second floor of the Otherworld Brookhaven Hospital in Silent Hill 2. The battery is on small ledge of a wall marked by outstretched hands, and is picked up simultaneously with a basement key.
The dry cell battery can only be used to replace the battery inside the flashlight. This only happens during James Sunderland's journey beneath the Silent Hill Historical Society, where he comes upon a small room with a key on the ground. Immediately after picking up the key, the flashlight goes out, apparently in need of a new battery. After using the battery, the flashlight returns to proper working order, except, James will find that the room is infested with Creepers, and he must solve the Creeper Trap Puzzle in order to escape.