When your ECM 830 first arrives you will need to remove an insulating tab from the battery compartment. This insulating tab is there to prevent the premature draining of the battery. The battery itself helps save your settings and log files. 

First locate the battery compartment at the base of the unit and simply pull the tab out:

Replacing the battery:

Replacing the battery is part of routine maintenance. 

1. Disconnect the unit from the mains power supply.
2. Remove the screw and swing cover to the side.
3. Slide battery out from under the clip.
4. Install a Lithium Coin Battery: 3V, 16mm type CR1620 by sliding under the clip. Positive side faces out.