4 x 1.5V AA batteries (Not Included) Any AA battery can be used, however for best utilisation of the capacity of the battery we recommend the use of Lithium Batteries (i.e. Energizer Ultimate Lithium Batteries.)
When the Details dispenser needs new batteries, open the front of the dispenser and remove refill bottle. Behind the bottle is a battery door just under the control button.
To open the battery door you will need an Allen key size 3.
See video for demonstration here: