Hi There
Mike, To add to the discussion, say the battery is old, it`s
internal losses are high. Internal losses are the batteries own way of
eating volts by it`s self....... That is why a battery goes flat over time
even when it is disconnected from the car, a new battery has less internal
losses than an old one, so that is why old inefficient batteries are hard on
vehicles electrical systems, as they require more output from the alternator
to make up for those losses.
So on start up, the starter has eaten a lot of volts turning the engine
until it finally fires up, with the engine running the alternator is turning
thus able to put back in what has been taken out and will work flat out to
do so, this represents load on the engine though as time progresses and the
voltage of the battery is brought up to match that of the output of the
alternator, as this happens the load on the alternator and thus the engine
diminishes to a state where it has made up for the start up losses...... As
I typed previously, if you then switch on various loads the alternator will
match them, so on a warm bright day after the start up losses have been made
up, the alternator will have an easy time matching the load of the gin
circuit losses, the occasional turn signal and brake light. On the other
hand If the driver jumps in on a cold night switches on the headlights looks
around for his keys, accepts a call on his mobile puts the stereo on for
some background..........1/4 hr later if the car starts the poor alternator
will have a real hard time to replenish the voltage, if the belt is in any
way weak, boy will it screech, and get warm and still screech until the
loading on the alternator starts to lessen with time as the voltage in the
battery is replenished...... it`s a balance kinda thing ?
Time plays a big part in voltage measurement in battery systems, I guess
that is why batteries are sized in ampere hours as well as voltage, an
ampere hour is a load of 1 amp for one hour...... a 100 ampere hour battery
can supply 1 amp for 100 hrs or 100 amps for 1 hour or 50 amps for 2
hours......... You get the picture.
So strange though it may seem, a starter motor can take a peak surge
of....say...600amps on a cold day, though this is over a very short time and
lessens as the plugs begin to fire up the engine, it still has represented a
huge load and thus volt drop in the battery, so when the alternator is in
circuit with the engine running is sees and meets the deficit or if you
prefer the now low voltage of the battery is seen by the regulator in the
alternator thus the alternator works hard to sustain it`s output voltage and
thus will bring the battery up to match that output voltage....... So it can
be seen that as the battery voltage rises the load on the alternator lessens
? It`s a voltage/time kinda thing ?
I guess a warm belt may grip the pulleys better, though a slack belt will
screech more hot or cold, I`m sure if we brought belt material age and
temperature and loading in to the issue we could indulge in some formula
that would baffle Einstein (-:
Alternators produce ALTERNATing current AC Which is rectified to DC
within a diode pack or rectifier enclosed inside the alternator. DC being
required to charge batteries
Dynamo is a means of generating DC power direct......... Dynamo`s are often
called Generators. though in industrial terms generators can be many
things.
Wotcha think ?
Cheers, George.
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