The Key
The key is in a secret compartment in Captain Ziggs' quarters atop the Hub. You will need to cool the hatch, defeat the underground monster, and solve the mazes, and that will power the elevator at the upper left of the Hub. (Throw the switch at left to start the Hub turning.) In the bedroom, use the code (0516) to open the compartment and get the Bridge Key and Mech Weed Whacker.
The Steam Generator
You use the Steam Generator on each of the three doors, once you have the key. For each, you will adjust the steam path through the connectors so that the input (10) is raised or lowered to the necessary pressure.
Sully's Door : create a path totalling -5 (output has to be 5)
Bridge Key : create a path totalling +6 (output must be 16)
Living Quarters : create a path totalling -3 (output must be 7)
The path you have will vary, but for the Bridge, try to include as many +2 as you can.
At Sully's, the terminal indicates that it needs a steam pressure of 5. Using the Steam battery, which has a base pressure of 10, you need the connectors to equal -5 (10-5=5). Shift the path of the connectors away from the +2 and +1 valves, and toward the -1 and -2 valves. You should only have to move three or four to get the proper -5 in the indicator dial.
(more at the related question below)
in the trash
Enter steamworks island and go left. It's RIGHT THERE
Use it for the steam terminals
in the elevator there is a secret room with a skeleton that is where it is
on the trash can
it is in sully's steam powered paraphernalia
yes there are many bateries
There are no ghost on steam work island
The Steam Battery is in the garbage bin on the side of the Clockwork Cantina, which is just to your right when you enter the island.
You use the steam battery in Gear Alley. On number 5.
The Steam Generator (to open the doors) is in the trash bin to the right of the Cantina.
you have to get the number: minus five