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Millions of batteries are used in America for automobiles, aircraft, portable lights, and emergency power installations. The ability to install, test, charge, and maintain storage batteries is an important asset to any well-qualified apprentice electrician. CELLS The basic unit of the battery is the cell (Figure 1). A battery is usually a group of separate cells connected in series. The number of cells used depends on the total voltage required. Primary cells and secondary cells are types of cells widely used in the electrical field. Primary cells are commonly known as dry cells. This type can be used only once. When discharged, they are commonly discarded. The secondary or storage-type cell, when discharged, can be recharged by passing direct current through it in the proper direction. Primary cells Two common types of storage cells are the nickel-cadmium cell and the lead-acid cell. The lead-acid cell is used extensively. TRADITIONAL BATTERIES The internal feature...

The NEC establishes some very important fundamentals that weave their way through the decisionmaking process for an electrical installation. They are presented here in brief form and are covered in detail as required throughout this text. The NEC defines a branch circuit as The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).* See the next Figure. In the residence discussed in this text, the wiring to wall outlets, the dryer, the range, and so on, are all examples of a branch circuit. The branch circuit is that part of the wiring that runs from the final overcurrent device to the outlet.The rating of the overcurrent device, not the conductor size, determines the rating of the branch circuit. Feeder conductors are circuit conductors between service equipment and the final overcurrent device. The NEC defines a feeder as All circuit conductors between the service equipment, the source of a separately derived system, or other...