Battery Charging
WARNING: This page is about a different car, the 2016 Ford Transit Connect. However, it is still accessible from the selected car via links, so may be relevant.
When it is required to charge the vehicle battery, connect the positive connection to the battery positive post, and attach the charger negative connection to a body or engine ground. The placement of the battery is such that the battery negative terminal is located under a sheet metal shroud making sheet metal ground the obvious choice for the charger.