For a battery installed in a vehicle, connect the black clip to a heavy metal part of the engine block or frame away from the battery. If the battery is outside the vehicle, connect it directly to the negative (-) terminal. Power On: Plug the charger into a grounded AC outlet. 3. Setting the Charge

Use a wire brush to remove corrosion or gunk from the battery posts to ensure a strong electrical connection.

Do not plug the charger into a wall outlet until after the clips are connected to the battery.

Take off all metal jewelry, as it can conduct electricity and cause a short.

NAPA chargers range from manual models to "smart" microprocessor-controlled units. Napa Battery Charger and Noco Genius 10 - How They Work