Battery usage varies based on your pet and your yard. However, battery usage tends to be 1 - 3 months with the wireless system and is typically lower when you first get the system and are training your pet.
The receiver collar uses an RFA-67 battery. The collar has a low battery indicator light which will flash 4-5 seconds when your battery is low. If this light is flashing, replace the battery.
If you wish to test the battery:
To replace the battery, use a coin or the flat side of the test light tool. Insert the coin or test light tool into the top of the battery and twist the cap to the "off" position. Remove the cap and replace the new battery, twisting it into place, aligning the arrow with the "locked" image on the collar.
You can increase the battery life by turning to collar off when it is not on your pet or needed for containing your pet such as at night.