FORD 2012 Focus v.1 - Manual (Page 344)

To ensure proper operation of the battery management system (BMS),
any electrical devices that are added to the vehicle should not have their
ground connection made directly at the negative battery post. A
connection at the negative battery post can cause inaccurate
measurements of the battery condition and potential incorrect system
operation.
Note: Electrical or electronic accessories or components added to the
vehicle by the dealer or the owner may adversely affect battery
performance and durability and may also affect the performance of other
electrical systems in the vehicle.
When a battery replacement is required, the battery should only be
replaced with a Ford recommended replacement battery that matches
the electrical requirements of the vehicle.
WARNING: Batteries normally produce explosive gases which
can cause personal injury. Therefore, do not allow flames, sparks
or lighted substances to come near the battery. When working near the
battery, always shield your face and protect your eyes. Always provide
proper ventilation.
WARNING: When lifting a plastic-cased battery, excessive
pressure on the end walls could cause acid to flow through the
vent caps, resulting in personal injury and/or damage to the vehicle or
battery. Lift the battery with a battery carrier or with your hands on
opposite corners.
WARNING: Keep batteries out of reach of children. Batteries
contain sulfuric acid. Avoid contact with skin, eyes or clothing.
Shield your eyes when working near the battery to protect against
possible splashing of acid solution. In case of acid contact with skin or
eyes, flush immediately with water for a minimum of 15 minutes and
get prompt medical attention. If acid is swallowed, call a physician
immediately.
WARNING: Battery posts, terminals and related accessories
contain lead and lead compounds. Wash hands after handling.
Maintenance and Specifications
344
2012 Focus (foc)
Owners Guide, 1st Printing
USA (fus)