An automotive electrical system normally has one or more power accessory points. These accessory points are often cigarette lighter outlets. However, most vehicles manufactured since the 1990s contain dedicated power accessory outlets.
Many automobiles have their cigarette lighter outlets wired so that the outlets only work when the automobiles are running. However, power accessory outlets are usually hard-wired to the battery, and are always active.
A power accessory outlet may also be used as a means to trickle charge an automobile battery. Some accessories, such as solar battery chargers, are designed to take advantage of the bidirectional nature of a hard-wired power accessory outlet.
Place the solar battery charger, shiny-side up, on the automobile's dashboard.
Plug the battery charger plug into the power accessory outlet.
Allow the battery to charge for approximately six hours, and then unplug the charger from the power accessory outlet.
Check the battery every half hour while it is charging. If the battery begins to bubble, or is hot to the touch, unplug the battery charger immediately.