To obtain infinite battery energy, follow these steps:

Navigate to your Outlast settings: C:\Users\[your username]\Documents\my games\Outlast\OLGame\Config

Look for OLgame.ini within that folder and open it with Notepad or a similar text-editing program.

Search for "bat" (without the quotation marks) and that search should lead to a series of lines in the file that appears about as follows:

OLGame.OLCheatManager]

bCheatsEnabled=false

bUnlimitedBatteries=false

Update the setting of the second and third lines so that they read "true" instead of "false" and save the file. When you play next, you'll have infinite battery energy.