Max Alternator Output

radensb

Actually, it is showing the capacitor in parallel with the amplifier, which is correct. But I agree the diagram is not drawn very intuitively.

Capacitors are only of use in certain situations.

1. The car alternator has to already be up to the task to power the system.
2. The type of music that is played.

Typically, audio amps are rated for peak power, which is rarely ever reached. Most of the time, you are running RMS (root means squared) power, so keep that in mind.

The caps can help lower the instantaneous power demands of the amplifier from the cars power system during high current bursts (heavy bass bump) because it can supply the needed current faster than the battery can. (a cap is just a battery at heart and looks like an open circuit component once charged thus it doesn't draw anymore current but can supply it when needed) It IS still a load on the cars power system while it is being charged. If you have music that is playing heavy beats that are hitting back to back, over and over again, you will never give the cap time to charge, and thus render it useless (and additionally an extra strain on the power system).

The charge time for a 3 farad cap is not trivial. Lets assume that the resistance in the wire from the 12 volt battery to the 3 Farad cap is 0.5 Ohms. That means it will take 1.5 seconds to charge! If your resistance is 1 Ohm, the charge time increases to 3 seconds.

The point of a cap is not to supplement the power responsibility from the alternator. Rather, it is there to help regulate current spikes and voltage drops caused by the inherent rapid power demands that audio amplifiers introduce.

SouthArk370Z

Where is power coming from? Or is it not shown and that is the "not drawn very intuitively" part? The more I look at that page, the more I'm inclined to believe that the writer doesn't fully understand the subject.

Edit: I found it! The power connection looked like a pointer to me. My bad.

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zakimak

It's like the writer already came to a conclusion that it is of no value and wrote it to support the conclusion. Once challenge, muddle the water by making non sensible statements. Let's dissect


"Because they don’t produce any current in and of themselves"

Of course not that's not what it's meant to do but do provide power in unrelated ways - via the alternator. Much like the alternator doesn't produce any power and of itself UNLESS it is driven by the motor



"They buffer current flow behind the “voltage wall” and redirect it away from their intended devices: the amplifiers!"

"Voltage wall"? - WTF? Only if the alternator cannot supply the current during the lulls in the demand. Since it's intention is for music reproduction (we don't listen to sine wave), it is not constant (like lights for example).



"Your car audio system is running mainly off your alternator, not your battery because its voltage potential is 12.7 V, whereas your alternator supplies 14.5 V. Since the alternator has the highest potential, it will supply the demanded current up to its point of saturation, whereby the battery takes over to supply the extra spikes of current demand."

1. Unless the car is not running
2. Voltage is not current - psssss P = V * I (power = voltage times current)
3. Bingo - The battery is a crude or low discharge/charge cap!!!! - don't forget the voltage drop



"Of course, this doesn’t happen with home audio amplifiers because their current source is unlimited for all intents and purposes (due to high voltage). This is the reason why some home audio amplifiers can have built-in banks of buffering capacitors that don’t cause a decline in voltage and current."

hahaha...and car audio amps doesn't have them....Current Unlimited?....no something call a breaker limits that in the house.



"Since the capacitor’s +ve and –ve terminals are directly connected to the terminals of your amplifiers, it actually acts as a buffer for the headlights - NOT for the amplifiers!"

No - your lights demands are constant. your amplifier demands are not. Like toilet versus running the taps. That little tank is what gives you the volume (amperage) demand.




"Remember: the accessories (i.e. headlights) and the current output by the alternator are BEHIND the “voltage wall” of the capacitor. The current generated by the alternator is directly available and pulled by the car’s accessories due to the path of least resistance and the buffering action of the capacitor. And this happens because the capacitor’s voltage DROPS when drained by the amplifiers. Since the voltage potential is higher at the alternator end, which is BEHIND the capacitor, the accessories have a more stable voltage and current supply than the amplifiers do as the capacitor is slowly charging. The amplifiers are directly connected to the capacitor so they will also see a corresponding drop in voltage on their terminals, whereas the headlights won’t (because they are connected to the alternator & battery). Therefore, less available current is supplied to the amplifiers than is demanded; again, because there is a limited amount current available in this automotive system. The voltage on the amplifiers will fluctuate with every discharge and charge of the capacitor. But the accessories behind the capacitor won’t see such a drastic fluctuation in voltage or current; thus reducing the flickering of headlights. The capacitor is actually reducing the spikes of current demanded by the subwoofer amplifiers each time the subs hit hard. Hence, your audio fidelity is somewhat compromised."

WTF and completely backwards




BUT MY HEADLIGHTS ARE FLICKERING, WHAT CAN I DO?

Whatever you do....don’t add a capacitor! It’s a waste of money. You are better off putting your money towards the BIG 3 upgrade to your alternator’s wiring using 0-guage stranded wire. This is known to solve most of the headlight flickering problems while still maintaining the fidelity of your audio system. If the BIG 3 upgrade doesn’t reduce your headlight flickering issue, then you have saturated the output stage of your alternator. An additional battery may slightly help your situation, but it will place added charging stress to your alternator and most likely, reduce its life. The last resort is to install a high-output alternator of 160+ Amps. This will remedy all of your electrical problems, but it will require the BIG 3 wiring upgrade

1. Large wiring prevents voltage drops from the alternator to the amps that's it. It doesn't stop your headlight flickering...sheesh

2. Additional battery okay though? hahaha. It prolongs your buffer BECAUSE it has large reserve but Run it hard and guess what is happening with your under capacity alternator?



"The current produced by the car’s alternator is difficult to get past the capacitor “voltage wall” and onto the amplifiers. The pernicious capacitor steals current from the amplifiers and gives it to the accessories (lights, ignition, A/C, defogger, etc). It acts like a fluctuating “voltage wall” that prevents a portion of the alternator’s otherwise, available current, from ever reaching the amplifiers. A capacitor does NOT produce any additional current in the system; it just re-distributes current in a way that is detrimental to the audio fidelity of your system."

"Voltage wall" - hahaha...I don't know where to begin with this conclusion. Rather than go into specifics I'll highlight one poster's response.
.

an audio system has an average (not just peak, but average) power consumption that leads to the total automobile electrical power consumption (lights, fans, audio, etc.) exceeding the capacity of the alternator then the only possible solution is producing more power: get a larger alternator.

If the average power consumption is within the capacity of the alternator then having some way to smooth out the demand on electrical system could be beneficial. That is reason why capacitors may be beneficial. The same reasoning is also behind having an extra battery. However, unless the capacitor or battery is able to supply power at the same voltage as the alternator then there will still voltage sag. For example, having a 14.5 volt alternator backed up by a 12 volt battery does nothing until the voltage drops to 12 volts.

However, in general the electrical loads are all parallel so with properly sized supply wiring the presence of a capacitor will not lead to under powering an amplifier or divert power elsewhere. Electrons do not delivery addresses.

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SouthArk370Z

Wow! Quite a write up. Thanks for taking the time.

I've always though of using capacitors for automotive voltage droop to be a lot like using oil additives in a worn out engine - it might mask some symptoms but it really doesn't do anything to fix the problem. If you want to thump, you have to have the power; get a bigger alternator.

Besides, I wouldn't want a 3F cap in my car - those things can be very dangerous, even at 12-15V.

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