First, I would like to raise the possibility that the controller is no longer working, it's hard to tell from the information available.
Second, if you don't know the management port IP, then the only way to access the controller is with the serial port.
But first, the default IP of the management port is 10.0.0.1. You can try to access the unit with the default IP. You'll need to connect a laptop directly to the management port and set the laptop's ethernet port IP to 10.0.0.100 (or any valid IP different from 10.0.0.1). If the controller is at the default IP you should be able to connect to the CLI via telnet (putty will do this for free) or WebPAM from a browser.
Lastly, if the controller battery is dead, then you will need a serial port connection as the controller will require that the date and time be entered before booting.