For a guy with such a big mouth, you really are ignorant to the ver
fundamentals of how a car electrical system works.
I -seriously- am shocked!
thelizman wrote:
*geolemon wrote:

ONLY if the -average- current draw exceeds your alternator's
capabilities do you have a -charging- problem...

That's oversimplified - and wrong. If the cables are corroded, the
biggest alternator in the world won't charge. If the connections are
corroded, the same. *
No one mentioned corrosion here.. if there's corrosion, that's
separate issue.
Your argument is like saying the geometry of your car's suspensio
doesn't matter, because you might get a flat tire.
*
Even smallish amplifiers can yield peak current demands which will
exceed even a large alternator's supply capabilities...

"Peak" does not equal "average". Even a large amplifier - on averag
-
doesn't drain more than a couple of amps of current, and transients
"peaks" only last a fraction of a second. These peak current draw
are
buffered by the amplifiers internal capacitor banks, and recharg
demand
is handled by the cars battery, because alternators simply don'
react
fast enough.
*
Exactly my point, with regard to the difference between "peaks" an
"average" current draw.
That's as I spelled it out.

And yes, capacitors that are on the rail-voltage side of the powe
supply are much more efficient - particularly the higher in impedanc
you go on the load side of the alternator.
More efficient, in terms of "stiffening" the amplifier's ability t
supply the output that it's supposed to.

Break that mindset.
I'm not talking about what a capacitor does to the output of a
amplifier. That's not relevant in the scope of my post at all.

I'm discussing the load that the amplifier places on your car'
electircal system... and simply that.
I'm discussing what happens when you exceed the current supply of th
alternator:

And when that happens, the voltage drops to the 12v level of the
battery so that it can kick in the few extra amperes that the
alternator can't for those brief moments in time...

That's wrong, way wrong. Voltage plays no role in which componant
supplies current. The battery and alternator always share the tota
load
of the cars electrical system. When current demands exceed that o
the
alternators output capability, the battery (which has many times the
reserve of any alternator) shoulders a greater share of the load.
Voltage doesn't make any difference - the voltage doesn't even nee
to
drop for this to occur.
The battery and alternator do share the load, that's my point.
As long as your average current draw (not peak!) is lower than th
average current output supply capability of the alternator (factorin
RPM and all that), then you will not have discharged your battery ove
the duration of that usage.
All is healthy... despite the fact that you might have had severa
light-dimming "holy cow" current draw moments, maybe even exceedin
175a!

Here's a scenario for you:
During an hour-long listening session, let's say my average curren
draw was around 15a...
During that time, I had two transient peaks that reached a huge 150a i
terms of current demand on my electrical system.
Are you advocating, that because my alternator is say, only an 80
alternator... that warrants my replacing my alternator?

What I am saying is that's ludicrous thinking.
Until you have a charging problem, replacing the alternator doesn'
make sense.
And until your -average- current draw becomes excessive - relative t
the capabilities of your stock alternator - you shouldn't replace it.


There -are- downsides to aftermarket alternators, whether you choose t
believe that or not (that's a personal problem). It can be measured..
in more ways than just the pocketbook.


The capacitor smooths the transition from alternator to battery,
There is no "transition".
Let me get this straight..
You actually are stating that the voltage will not fall when th
alternator's current capabilities are exceeded?
You are stating that the load on the battery does not rise, the
battery is not the thing "picking up the slack", supplying the
current that the alternator cannot?

In other words... let's for example assume at a given RPM an
alternator is able to supply 100a of current, at a 14.4v level.
Let's say you start to draw 150a.
Are you trying to claim that the voltage will not drop to the 12v
level of the battery, when this happens?

This is a very simple test that you can do with a voltmeter, if you
don't have one installed in your dashboard. Easy to do, with a CD of
test tones, and your volume knob, if you have an amp that's capable
of drawing those current levels.



Your light bulbs dim simply because light bulbs are brighter on
14.4v
than they are on 12v... that's not a sign of a charging problem.

Again, you ignore current. I'd like to see you light a household
light
bulb with 10 AA batteries, and see how bright it gets. The dimming
is
because of a lack of current. The dropoff in voltage is a symptom,
not a
cause.

No...
The light bulbs getting dimmer is a symptom of the voltage dropping.
The voltage dropping is a symptom of something else... the current
capabilities of the alternator being temporarily exceeded.

Two unrelated things...
But people "believe" that they are buying a capacitor to help light
dimming.
In actuality, they are buying a shock-absorber for their electrical
system... and a nice side effect is that headlight dimming is
reduced.

I suppose you believe headlight dimming is just as dramatic without a
capacitor as with?



quite
dramatically even.. the results can be seen in greatly reduced
headlight dimming, as there's a nice [relatively] slow transition
down
to 12v now, rather than a temporary, sudden slam to even below 12v
every time there is a large transient peak.

This may come as a newsflash, but there are capacitors built into
amplifier power supplies, and generally they supply sufficient charge
for normal operation.

Yes, capacitors are much more efficient on the rail voltage side of the
power supply than the supply voltage side.
Sufficient charge?

Remember, we aren't talking about the performance of the amp... I'm
talking about the demand on the electrical system that the amp places.
If your amplifier is demanding 150a for a transient peak... is that a
sign that the amplifier has enough internal capacitance? ;-)

That being said, we must now be concerned for what happens, when the
amp does demand 150a from your electrical system.
That's the point, and that's when I say the capacitor can behave like a
shock absorber, because the battery WILL be suddenly called heavily
into play to provide that which the alternator can't.
Voltage will drop, and the moment voltage drops, the capacitor begins
discharging, helping supply, until the battery is providing enough
current where the alternator and battery are equalized again, supply
meeting demand.
--
geolemon
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