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Chapter 4 Electrical and Hydraulic Systems
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Equipment Operator Basic - Beginning construction equipment operators manual
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caps and the terminal post protrude from the cover. In other batteries, only the filler caps extend above the cover  and  the  terminal  posts  extend  through  the  side. The   latest   design   of   batteries   is   the   so-called maintenance-free batteries that provide no means of checking the electrolyte or water level. dc charging system (fig. 4-2, view A) or an ac charging system (fig. 4-2, view B). Both systems generate an alternating current (at); however, the difference is the way they rectify the ac current to direct current (de) for charging the battery. Dc  Charging  System Battery  Capacity The  capacity  of  a  battery  is  measured  in  cold cranking amps (CCA). The CCA capacity is equal to the product of the current in amperes and the time in hours during which the battery is supplying this current when   cranking   a   cold   engine.   The   ampere-hour capacity varies inversely with the discharge current. The size of a cell is determined by its ampere-hour capacity. The capacity of a cell depends upon many factors. The most important of these factors are the following: (1) the area of the plates in contact with the electrolyte; (2) the quantity and specific gravity of the electrolyte; (3) the type of separators; (4) the general condition of the battery (degree of sulfating, plates buckled, separators warped, sediment in bottom of cells, etc.); and (5) the final limiting voltage. CHARGING SYSTEM The  charging  system  performs  two  jobs:  (1)  it recharges the battery and (2) it generates current during operation.  The  two  types  of  charging  systems  used  on automotive   and   construction   equipment   are   a A  dc  charging  system  has  a  generator  and  a regulator.  The  generator  supplies  the  electrical  power and  rectifies  its  current  mechanically  by  using commutator bars and brushes. The regulator performs three jobs: (1) it opens and closes the charging circuit, (2) it prevents overcharging of the battery, and (3) it limits the output of the generator to safe rates. Ac  Charging  System An ac charging system has an alternator and a regulator. The alternator is really an ac generator. Like the generator, it produces an ac current but rectifies it electronically, using diodes. Most alternators are more compact than generators of equal output and supply a higher  current  output  at  low-engine  speeds.  The regulator in an ac charging system limits the alternator voltage to a safe, preset value. Charging  System All 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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