Not all Wireless Home Monitors use battery power, some require a connection to a power source. The LW2760 for example, needs power from the adapter to continuously view the monitor. If a battery was not included for a monitor refer to the Quick Start Guide included with your wireless monitor, or the product specification sheet to confirm that the unit uses a battery pack. Click here for downloads and documentation for your product.
If you have confirmed that you should have received a battery and did not, contact Technical Support.