Stock Alternator

[ILoveMoney557]

Ok so this Wednesday I will be installing 2 Rockford Fosgate 12" T1's in my 07 scion. The amp powering these monsters is rated to have 4000 watts max. The subs are wired to the amp to have a 1200 Watt rms draw and have 2400 Watts peak power. Will the stock alternator be able to keep all of this powered while still being the normal everyday stuff.

[excelon72]

that makes about 2k rms on the amp? that more than able to be handled if you have a good battery. however your system sounds like an SPL system so a capacitor would be a good idea in combination with a yellow top ultima battery. i have 2200 peak and 800 rms(have all amps running at 4ohms for durability and quality) and with the ultima battery i dont even need a capacitor but you might.

[navylife59]

This is a very old thread but just to clear the air; the OEM generator is rated to 90A. At what RPM this is reached, I do not know. The tech pub does amperage load testing at 2K RPM. Technically speaking, the tech pub calls it a generator that which we call an alternator. Simply put, it generates AC voltage that is then converted via bridged rectifier diode set into DC current. The built-in regulator's job is to regulate (adjust) the voltage out put to stay within it's target parameters at all times.

Technically, all of the vehicle's power needs should be provided by the alternator. The battery can be removed while the engine is running and it should not change. The battery is intended as an offline power source to start the motor and can be used to operate accessories (temporarily) while the motor is not running. Once the battery is drained below it's standard voltage range of 13.2 - 14.8 VDC, the battery then becomes a load till it is charge back to capacity. Anytime the load rating of the alternator is surpassed, the battery's stored energy comes online as the battery begins to start feeding the load. Once the overload is passed, the alternator will then have to recharge the battery. This process takes time and is cumulative. This is not sufficient for the demands of a high power sub amp which causes the low bass to sound muddy. It can also manifest itself into the dimming headlights when it is excessive.

The stiffening capacitors are designed to discharge and recover much more quickly than that of a battery. This will keep the voltage from dropping during these times of excessive amperage loads that a sub-bass amplifier goes thru. Not only does it help to keep bass notes crisp in the music, but also helps to keep the amplifier from overheating. Be forewarned though that not all stiffening capacitors are spec'd to handle this type of load efficiently. There are plenty of cheap caps on the market that have poor discharge/refresh cycles which, in itself, can become a load once it's cycles reach saturation. Don't waste your money with cheap junk here. Buy only high quality.

Look at your amplifier(s) fusing. That is the max load the amplifier can reach before the fuse is blown. Actually, the amperage rating of the fuse can be exceed greatly for micro seconds before being heated sufficiently to melt the fuse material. Same with the max load of the alternator. It's max load value can be exceeded but that does not equate to any increase output as that is an engineered mechanical value. Your amplifier should also have a spec rating sheet or label that will tell you the average amperage draw at a certain voltage.

Amps used to be load rated at +13.8VDC back in the old days. Today, they are rated at +14.4VDC. Using Ohm's Law, you can quickly deduce that the more voltage you have, the more power output you will get from your amplifier. Remember, that your alternator is rated to produce voltages in this range but averages closer to the +13.8VDC. When the alternator is overloaded, voltage will drop. At first the battery will slow this process down as it's off charge level will start at +13.8VDC but will soon drop towards the standard static voltage of a battery at +12.6VDC. The more the voltage drops, the higher the amperage load for the same given power. As the amplifier struggles with the lower voltage, the excessive amperage causes the amp to run hotter. Also, Total Harmonic Distortion (THD) will rise as well. Now think about what is going on when you are parked with the motor cranking the tunes? I will leave that for ya'll to figure out.

[CadenceScion]

I would suggest spending the dough and get a Kinetik Power Cell HC1200. Optima batteries are great, but once you get into the 3000watts range, the optima is going to struggle to keep up, I know I had an Optima Yellow Top, then I upgraded to the Kinetik. I would also suggest a capacitor. For every 1000 watts equals 1 farad, so your want at least a 4 farad capacitor. I also compete in SPL competitions and have hit 142.0 dB, but I have 2 Kinetik batteries and a capacitor. Another option would be finding someone that would be willing to take your OEM alternator and have it rewound for a higher amperage that doesn't exceed 200 amps.

If you have time, look over my profile and you'll see what system I have and what I am using.

[navylife59]

Sadly, I had to give up the bump in my trunk a long time ago. My Trunk Monkey was getting pissed. Actually, after I left the car electronics industry for a life in computers, I just did not have a ride that I wanted to put a system. I plan on one day making the RS3.0 my audio car. I am going to sound deaden it while the interior panels are out to fix the hail damage. I have some audio equipment lying around that I am going to dump in there. Say, I have an old Lanzar Opti 500 arc-welder, hmm, I mean amplifier. I ran 2 10" Atomic 2-Ohm subs wired bridged for 1-Ohm. I hit 138db in a 1993 Mercury Sable GS station wagon.

[Djlilres]

Hey whats up?? What are you using for voice?

[CadenceScion]

Can you rephrase the question?

[navylife59]

Hey whats up?? What are you using for voice?

I don't understand what you are asking about.

[Djlilres]

if your putting bass in your car you might want to consider putting in mid-range door speaker along with some nice tweeters to get a clean full sound

[CadenceScion]

I agree w/ that comment as well. A nice 2-way or 3 way component set with silk dome tweeters will really make that interior sound come alive.

[navylife59]

That will always come out nicer. Our OEM tweets are just so-so.