Loose Terminal Clamps

• Marine batteries have two terminals positioned on the top of the battery. The boat wiring connects to the terminals via two thick wires, terminating in large metal clamps. To ensure good electrical contact there must not be loose connections. Constant pulling by the wires as the boat moves can quickly loosen the connections.
  
  

Corroded Terminals

• Marine batteries contain an acidic electrolyte. If this escapes, it may cause corrosion. More probable is corrosion caused by saltwater spray coating the terminals. This reacts to produce a layer of electrically insulating corrosion. This must be removed. A layer of petroleum jelly applied to the terminals prevents its return.
  
  

Loose Terminals

• Many batteries are fitted with screw-on replaceable terminals. If these are loose, their electrical connectivity is poor and the current from the battery is reduced. The terminals loosen from constant pulling, excessive tightening during maintenance and from the battery sliding around as the boat moves. Applying too much force when disconnecting wires from the terminals damages the terminals and the battery.