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CHARGING SYSTEM OF A CAR BATTERY AND HOW IT OPERATES

Jumper Cables Battery Engine Car Automotiv

All vehicles have a charging system which provides for their electrical needs, such as ignition, lights, heater and electrical accessories, while the engine, is running, as well as charging the battery. It consists of a generator, driven by a belt, and an automatic control system. Old cars made five or six years earlier are fitted with an alternator which is a form of generator for battery charging purpose while some commercial vehicles have different types known as the dynamo.

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In both the alternator and the dynamo, electricity is generated in the same way as it is at a power station. Either, coils of wire are moved near a stationary magnet (dynamo), or the magnet is moved near coils of wire (alternator). In each case, the moving lines of magnetic force generate electricity in the coils of wire. The amount of electricity generated depends on the speed at which the coils and magnet move relative to each other, how close they are to each other, the strength of the magnetic field and the number of turns of wire in each coil.

As the speed of a car engine changes continually, but the electrical requirements for such items as headlights or a heated rear window are constant, a method of controlling the generator output is necessary. That can be achieved by using an automatic control system to alter the strength of the magnetic field.

Practically, an alternator can produce higher output for longer periods of time than a dynamo. This is because the generating windings in an alternator are stationary and are not restricted in size, nor are they as difficult to cool as those of a dynamo, which rotates in its armature.

In practice, both the alternator and the dynamo start to produce a useful current output at armature speeds in excess of 1,500rpm. However, the dynamo armature is limited to about 6,000rpm. That is because of the effects of centrifugal force on its complicated windings, and also because at high speed, constant brush contact with the commutator is difficult to achieve.

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The armature, or rotor, in an alternator is not as complicated and can be turned at least three times as fast as a dynamo. This means that the drive-belt pulley fitted to a dynamo has to be quite large to prevent the armature turning too quickly, and the engine must be turning quite fast for it to produce a useful current. The alternator is fitted with a much smaller pulley and can produce a useful current at engine tick-over speeds.

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HOW TO CONNECT CAR BATTERY CHARGER

In winter, when cold weather makes the battery less efficient, a car used on many short stop-start journeys will consume a great deal of battery power each time the starter is operated, but the car may not travel far enough for the generator to put back the lost energy.

Under these conditions, a mains-operated battery charger that puts a ‘trickle’ of current into the battery while the car is packed overnight, will do the same job as a generator. As most home chargers have a low output, it is not necessary to remove the battery filler caps i.e the vent cover. New batteries should not have their vents or covers removed during charging since the electrolytes could overflow. Inflammable hydrogen gas is given off through the vent holes during charging, so battery charging should be carried out only in a well-ventilated area, and anything likely to cause a spark should be at least six feet away from the battery.

Here, the battery has been removed from a car, but battery charging can, if required, be carried out with the battery connected up and in position on the car.  Below are steps to be followed in charging of the car batteries:

  1. Check the electrolyte level and top it up if necessary, replace the filler plugs or vents cover.
  2. Connect the charger clips to the battery terminals. The positive clip (+) usually joined to a red cable goes to the battery positive (+) terminal. The negative terminal is joined to a black cable clamped on the negative battery terminal.
  3. Plug in the charger to the mains and switch it on. It should indicate the rate of charge on a dial or illuminate a working lamp. Most chargers make a humming sound. If the charger does not work, switch it off and check its fuse. If this has blown, check that the connections on the battery are correct. Accidentally touching them together when the charger is working will blow the fuse.
  4. When charging is complete, switch off the charger.
  5. After the switching it off, disconnect the clips from the battery terminals. A ‘live’ charger should not be disconnected at the battery terminals since it can cause a spark at that moment and cause the hydrogen gas being released to explode.

 

 

Originally posted 2018-10-07 18:59:59.

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