Batteries

 

Batteries

  • Lead Acid Battery:
    Made of lead dioxide (positive plate), sponge lead (negative plate), and sulfuric acid electrolyte. Chemical reactions between plates and acid produce electricity. Charging reverses the reaction. Rated by voltage, ampere-hours (Ah), and cold cranking amps (CCA).


  • Nickel Alkaline Battery:
    Uses nickel oxide (positive electrode), cadmium or iron (negative electrode), and potassium hydroxide electrolyte. Known for durability, rechargeability, and ability to deliver high current.


  • Construction:
    Both batteries have electrodes, separators, electrolyte, and a case. Lead acid batteries often need maintenance (topping up water), while nickel alkaline batteries are usually sealed.

  • Battery Rating:
    Indicates voltage, capacity (Ah), and maximum current (CCA for cars). Charging rate (C-rate) shows how fast the battery can safely charge or discharge.

  • Charging:
    Requires proper voltage and current control to avoid overcharging or undercharging. Lead acid batteries use bulk/absorption/float stages. Nickel alkaline batteries have different recommended charging cycles.

  • Testing:
    Common tests: voltage check, electrolyte specific gravity (lead acid), and internal resistance. Battery management systems help monitor health.


Starting System

  • Starting Circuit:
    Connects the battery to the starter motor via the ignition switch and a relay (solenoid). The solenoid allows a small switch to control a large current, protecting the ignition switch.


  • Starter Motor Construction & Operation:

    DC motor with armature, field windings, and brushes. When started, it spins the engine’s flywheel through a pinion gear, cranking the engine until it starts

  • Starter Motor Drives:
    Overrunning clutch and Bendix drive mechanisms ensure the starter motor engages the engine only during cranking, then disengages once the engine runs.

  • Solenoid Switch:
    Electromagnetic switch that connects the battery to the starter motor when the ignition key is turned, also moves the drive into engagement.


Charging System

  • Charging Circuit:
    After the engine starts, the alternator (or dynamo in older vehicles) recharges the battery and powers the vehicle’s electrics. The voltage regulator maintains a steady charging voltage.

  • Alternator Construction & Operation:
    Consists of a rotating magnetic field (rotor), stationary coils (stator), diodes (to convert AC to DC), and a regulator. Driven by a belt, the alternator generates electricity as the engine runs.

  • Regulators:
    Control alternator output to prevent overcharging. Modern systems use electronic regulators; older ones used mechanical regulators.

  • Dynamo:
    Older DC generator, less efficient than alternators, especially at low speeds. Now mostly replaced by alternators.


Key Diagrams (Just Describe—Replace with Images Later)

  • Battery: Show plates, separators, electrolyte (lead acid); electrodes and case (nickel alkaline).

  • Starting Circuit: Battery, ignition switch, solenoid, starter motor.

  • Starter Motor: Armature, field coils, brushes, drive mechanism.

  • Overrunning Clutch/Bendix Drive: Gear engagement/disengagement mechanism.

  • Solenoid: Coil, plunger, contacts.

  • Alternator: Rotor, stator, diodes, regulator.

  • Dynamo: Commutator, brushes, field coils.

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