Most electronic cigarettes employ a lithium-ion rechargeable battery to power the heating element. Battery life varies depending on the battery type and size, frequency of use, and operating environment. Many different battery charger types are available, such as wall outlet, car, and USB chargers. The battery is generally the largest component of an electronic cigarette.
Some electronic cigarette employ an electronic airflow sensor to automatically activate the heating element upon inhalation, while other models require the user to press a button while inhaling. Various other electronic circuits are usually employed as well, such as a timed cutoff switch to prevent overheating and a colored LED to signal activation of the device.
While some larger electronic cigarette models employ a user-replaceable standard-size battery cell, many models are too small to house a standard-size cell and instead require a proprietary component made by the electronic cigarette manufacturer. For those models, the battery and electronic components are housed within a single replaceable part.
