Hi There
Terry, I have no expertise in your proposed configuration, I
would however not worry that an alternator would overload your engine. I
would however make sure that the pulley on any proposed alternator is
compatible with your current "V" belt
If you will allow me to indulge myself with a little thinking in type ?
If we talk volts drop.....put on a light in the car however small and the
volts will drop over time if the engine ain`t running.... Eventually the
battery will be flat.
What is a flat battery...... One with not enough volts to do the job we want
it to.
Though there are a number of different jobs that a battery does for us, any
one of which will take volts from the battery.
The starter motor is the big one as it will drain the voltage from a battery
in a very short time.
Putting the volts back in....... This is where the dynamo/alternator play
their part. Part of the circuit for either of these components is a means of
measuring the battery voltage. this is generally called the REGULATOR
as it regulates the output of the alternator/dynamo (charging system). The
idea of the regulator is that it is that it measures the battery voltage and
switches the on the output of the charging system this output voltage is
above that of the battery, so the voltage flows to the battery to replenish
it to the correct level, when it reaches that stage the regulator switches
off the output from the charging system. So if we accept that the regulator
switches on at say 12v and off at 13.5v (generalising here) you can see that
the battery will be kept in a charged state ?
As long as the charging system is capable of matching the load of all the
electric's in the car then the battery voltage will be kept up......Or if
you prefer the battery will be kept in a fully charged state.
When starting the car on a cold morning, if it takes a fair bit of cranking
to get it started before it fires up, when it fires up is likely to be the
time of heaviest load on the charging system........ How many times have you
heard a fan belt that screeches for a few minutes after start up then runs
quiet ? That is because the charging system is under maximum loading trying
it`s best to put back in what has just been taken out. At this time the
charging system is loading the engine as you can not get electricity for
nothing........ If you like to think of it in Horse Power terms 746 Watts =
1 HP approximately I leave you to do the maths to suit your car......
running with a couple of 100 watt head lamps a couple of 5W tail lamps,
perhaps a couple of 3W numberplate lamps, the radio, heater....... It all
ads up to HP or fractions thereof......
If there is an ammeter fitted to the car you can monitor what is happening.
With the engine off, if you switch on any electric load, the meter should
deflect by an amount to the - side showing a discharge, the more you switch
on the more it deflects to the - or discharge side ?
When the engine is started, the needle should shift over to the + side,
denoting charge, or if you prefer charging system output.
The longer it takes to start the car the more volts are taken from the
battery and when the engine is started then the charging system is trying
it`s best to make up for the voltage losses of starting, so the ammeter
should confirm this after a start the ammeter will read high on the +or
charge side. until the battery voltage is replenished.
With the car running it is normal for a constant but low output from the
charging system to the battery, this should be reflected on the meter
reading low on the + side.
Some folk get real confused by thinking that electricity is too complicated
to understand though if you have a prob with that what if we think water
tank ? Ok, so the water tank in the loft supplies the water to the house,
if it overflowed it would flood the place and if it ran empty we would have
no water, what controls it, the ball (float) valve, as you draw water off
the ball drops and allows more water from the supply pipe to flow in to
maintain the level....... If you put on another tap to water the garden
then the level drops quicker and the ball drops more thus allowing more
water in...........until the ball has dropped and is hanging in mid air with
the water still dropping the level in the tank is still dropping......
Though if the tank and supply pipes have been correctly matched to the
likely usage (load) it should never run dry. So when the any tap is turned
off the load is reduced and the supply will play catch up until the ball
begins to float again and as it rises it may get to the stage where it will
switch off again even while the first tap is running, though may just float
up till the input matches the output. A kinda supply and demand situation in
balance ? So the supply pipe is the charging system, the ball valve is the
regulator and the taps in the house are the load.....easy ?
Terry this is one long way of saying that the load on the alternator is what
could slow your engine down a little at times, the reason is that an
alternator can put out voltage at a lower speed than a dynamo. in other
words when at low speed your dynamo was not charging and had no load effect
on the engine, however once the initial start-up voltage losses have been
replenished by the alternator then it will only be putting back what you are
taking out, so the loading from the alternator to your engine should be no
problem ? Assuming your Mog does not have a heated rear screen, heated
seats, air con and a computer in the glove compartment, sat nav and an ICE
system pumping up the volume ? In that case you can understand why new
style belts drive larger alternators at higher tension in order to sustain
the loadings without slipping. With a load of accessories it is easy enough
for the alternator to consume a horse power or more ! in that case with it
all running after a hard start and the engine at idle, I could see cause for
mild concern.
Hope this ramble helps someone somewhere, It is written in simple terms
cause I`m a simple guy, so if the professors amongst us could withhold their
compulsion to get into efficiency measurement etc, though if any feel I have
made any glaring mistakes.
Happy to discuss.
Cheers, George.
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