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. The alternator can supply the needs of a stock
electrical system and not give a hint of a charging problem. Its when
multi-amp systems go in that the deficiencies are borne out.
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 average -
doesn't drain more than a couple of amps of current, and transients
"peaks" only last a fraction of a second. These peak current draws are
buffered by the amplifiers internal capacitor banks, and recharge demand
is handled by the cars battery, because alternators simply don't react
fast enough.
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 total load
of the cars electrical system. When current demands exceed that of 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 need to
drop for this to occur.
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.
The capacitor smooths the transition from alternator to battery,
There is no "transition".
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.
Also, there is a lag time for caps too, and it is a function of the load
across the capacitors terminals. That is why manufacturers recommend you
locate the caps closest to the amps.
The amount of charge stored in a capacitor is huge. There's a reason the
directions advise you to charge the cap through a resistor with the
engine running. You're not going to drain a 1 or 1/2 farad cap so that
it can't deliver at least 12 volts with a car audio system.
Another downside on an alternator (besides the high expense,
possibility of it being largely ineffective without setting your idle
speed north of 2000RPM,
There's no need to idle up. A quality alternator is rated for output at
idle. Otherwise, you can just slap a larger pulley on the alternator.
and installation considerations that have been
mentioned) is the fact that a bigger alternator is a bigger drag on
your engine... and it's a bigger drag all the time, not just when you
need it.
Wrong. An alternator only requires more torque when the demand placed on
it increases.
A larger alternator is more difficult to spin, inherently. Bigger
rotor, larger magnetic forces... they can really impact your car's
performance, robbing horsepower.
Most aftermarket alternators are no larger in size than their stock
componants. The difference is in the number of turns in the coil, and
the increase in mass of the windings in negligable.
This is anywhere from "noticable" to "really bad", depending on what
kind of car you have... with most cars nowadays, you can feel a HP loss
just from switching on your air conditioning... I wouldn't want that
kind of loss on a permanent basis, much less one that was even
potentially worse...
Hope you never turn your air conditioner on.
Particularly when you consider that no matter how large of an
alternator I am able to buy, I'll likely still be able to produce a
transient burst large enough to temporarily exceed the amperage of the
alternator.
Which is what the battery is for.
And even then, that transient burst won't matter much in the grand
scheme of things...
Then why are you telling this guy to buy a cap?
You are full of information. MIS information.
--
thelizman "I didn't steal the FAQ either"
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