caps and the terminal post protrude from the cover. Inother batteries, only the filler caps extend above thecover and the terminal posts extend through the side.The latest design of batteries is the so-calledmaintenance-free batteries that provide no means ofchecking the electrolyte or water level.dc charging system (fig. 4-2, view A) or an ac chargingsystem (fig. 4-2, view B). Both systems generate analternating current (at); however, the difference is theway they rectify the ac current to direct current (de) forcharging the battery.Dc Charging SystemBattery CapacityThe capacity of a battery is measured in coldcranking amps (CCA). The CCA capacity is equal tothe product of the current in amperes and the time inhours during which the battery is supplying this currentwhen cranking a cold engine. The ampere-hourcapacity varies inversely with the discharge current.The size of a cell is determined by its ampere-hourcapacity. The capacity of a cell depends upon manyfactors. The most important of these factors are thefollowing: (1) the area of the plates in contact with theelectrolyte; (2) the quantity and specific gravity of theelectrolyte; (3) the type of separators; (4) the generalcondition of the battery (degree of sulfating, platesbuckled, separators warped, sediment in bottom of cells,etc.); and (5) the final limiting voltage.CHARGING SYSTEMThe charging system performs two jobs: (1) itrecharges the battery and (2) it generates current duringoperation. The two types of charging systems used onautomotive and construction equipment are aA dc charging system has a generator and aregulator. The generator supplies the electrical powerand rectifies its current mechanically by usingcommutator bars and brushes. The regulator performsthree jobs: (1) it opens and closes the charging circuit,(2) it prevents overcharging of the battery, and (3) itlimits the output of the generator to safe rates.Ac Charging SystemAn ac charging system has an alternator and aregulator. The alternator is really an ac generator. Likethe generator, it produces an ac current but rectifies itelectronically, using diodes. Most alternators are morecompact than generators of equal output and supply ahigher current output at low-engine speeds. Theregulator in an ac charging system limits the alternatorvoltage to a safe, preset value.Charging SystemAll charging systems operate in three stages: (1)during starting, the battery supplies all load current; (2)Figure 4-2.—Charging systems.4-2
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