Batteries are not included for this device and you need to purchase them separately. Insert two batteries of type UM1, R20 or D-cell. Please make sure to insert batteries with the correct polarity as indicated by the + and - symbols. Notes: * When you use the device indoors, we recommend using the AC power supply instead of batteries * When you use the AC power supply, or you do not use the device for a long time, please remove batteries from their compartment