Once again, the OEM battery and alternator are just fine for most systems. It's only when your system is drawing hundreds of amps (very unlikely - but say at an SPL competition, during a 'burp'), that additional batteries would help. The other reason to get multiple batteries would be for extended engine off listening time at 'regular' listening levels. It's all about the charge/discharge rate, and nothing beats the bank of small caps inside each amplifier. Next would be an external capacitor, mounted very close to the amplifier's power input terminals. The deep cycle batteries have the slowest charging and discharging rates; even worse than the OEM battery. For this reason, they're more of a burden on the electrical system. If the system is designed for SPL competition - multiple quick discharge batteries are about the only option because of the amount of current needed over 30 seconds. The goal should be to increase the wire gauge to lower resistance (raising voltage) to each amplifier. I've yet to see a daily driver that "needs" any additional batteries for the sole purpose of curing the dimming lights issue.

 

lol i must be doing something wrong becuase im running a 600 watt amp but tuned down to 500 watts for a 500 watts rms sub and im running only my optima and my lights get reduced to about 2/3 of the full lighting capacity so it looks i lose a 1/3 of my output when the sub hits hard its a single 12" in a sealed box
im doing my big 3 once i get my car back. already got wire

 

How exactly did you "tune down" your amp???

If you're going to say "with the gain ****", I can tell you that your amplifier will still reach full output potential, but will require a larger line input voltage (RCAs). Conversely, with the gain **** cranked all the way up, a smaller input signal will make the amplifier reach full output power - and too large of a signal will clip the preamp, or overdrive the amplifier. There is no "power choke" method to de-tune the amplifier, other than limiting the power input voltage (inadequate cable size, low supply voltage, etc.).

Gain ***** are a level matching device, intended to compensate for different efficiency speakers and/or size amplifiers.

 

I was building solid state amps with 0.25 ohm dc coupled outputs and flat frequency response down to 3Hz before you were born and am now working with 150 amp circuits for Electric Vehicles with switching amplifiers operating at 30khz using Hawker batteries that output 1400 amps - so when I say that a big low impedance Red Top at the amp input terminal solves the voltage drop problem I sort of know what I am talking about. I regularly power cycle "car" batteries with 100 amp charge and 50 amp drain loads and see a 3 volt swing at the battery terminals. There are chemical reactions in the wet cell that just don't happen very quickly to keep up with bass notes. Also a Farad cap is going to drop 1 volt in a second at 1 amp discharge or at 10 hz at 10 amps - it will take a bunch of farad caps to handle a 50 amp surge without a big voltage drop. Also the Red Top is a starter battery not a deep cycle.

 

Wow...

Let's take your beloved Optima Red Top (starter) battery for example. I looked at their website, and found a nice round number of 1000CA on their largest model. Cranking amps (CA) is the amount of current a battery can provide at 32 °F or greater. The rating is defined as the number of amperes a battery (at that temperature) can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery). Peukert's Law expresses the fact that the capacity available from a battery varies according to how rapidly it is discharged. A battery discharged at high rate will give fewer ampere-hours than one discharged more slowly.

That being said, I submit that NO street stereo system will draw anywhere near 1000amps - especially for 30 seconds because music is dynamic. Add the fact that the alternator is constantly charging the battery. I realize there are additional loads on the charging system, but still - plenty of power is available for street systems. The Scion alternator in the tC is 100amps.

You stated: A farad is the amount of capacitance that requires one second for a one ampere flow of charge to change the voltage by one volt - which is correct. As I've mentioned before, the ESR of any capacitor is MUCH lower than a battery, and will therefore charge and discharge faster - maintaining a smooth voltage. Once again, I've yet to find an amplifier that can not sustain regular music play (re: not 'burps') when proper wire gauge is used, making the addition of an external capacitor unnecessary.

The car's alternator ampere rating plays the major role in determining how powerful an amplifier(s) you can install. Multiply the alternator's ampere rating by 40%, and you'll get a rough idea of how much reserve current capacity your car's system has.

To calculate the current draw of an amplifier, multiply the number of channels by the RMS watts per channel (a 4 channel amp rated at 100 watts RMS per channel would be 400 watts). Double it to account for amplifier inefficiency (400 watts X 2 = 800 watts), then divide by the average output Voltage of an alternator, 13.8 volts (800 divided by 13.8 = 58 amps). Since the average music signal requires about 1/3rd of the average power in a test tone, divide by 3 (58 amps divided by 3 = 19 amps). The result is the amplifier's approximate average current draw. In short, a 400 watt class A/B amplifier draws about 19 amps when playing music! Most people use a class D amplifier for their subwoofers, which are somewhere around 90% efficient, not the 50% figure I used for the class A/B amplifiers in the example above. So a 1000 watt class D subwoofer amplifier draws about 1100 watts at full power (rarely, if ever happens), and would draw somewhere around 27 amps while playing music. That's about 46 amps (19+27) of current draw while playing music - pretty loud. Again, since music is DYNAMIC, these numbers aren't constant, and will be lower most of the time, giving the alternator a chance to charge the battery!

A fast-and-nasty way to ballpark an amplifier's current draw is to divide the total fuse value of the amp by two. For amplifiers with multiple fuses, the rating of all fuses provided with the amp must be added together. This will likely produce a significantly higher estimate than using the proper formula. Although inaccurate, this will err on the side of safety.

School's out.

 

Very impressive but is a Lead Acid battery with some miles on it going to have the low output resistance needed to handle the bass surges and is the cost of 4 AWG or thicker wire going to cost less than a Red Top and it STILL only connects you to a used possibly tired car battery when all you need to do is put a good RedTop on the amp to handle it all with reasonable wire feeding it the average current you calculated that the alternator can provide. The fact that the lights are going dim indicates an aging car battery or some in line resistance in the power connection to the battery dropping the system voltage enough to be noticed.

 

I'm starting to think you work for Optima...

Why are you pushing Reds soo hard? If you scratch the surface, you'll find out that very few car audio competitors use Optimas. Why? Because they fail without warning. I've personally gone through 3 Optima batteries in 2 years (previous car). I've mentioned a few other great "stereo" batteries in previous threads, to include:

http://scosche.com/efx.aspx?CategoryID=51

http://www.svrbatteries.com/

http://www.kinetikaudio.com/

http://www.batcap.net/

However, I'll let you in on a little secret...I've competed for 2 seasons with a 1600 watt system, put my car though 2 brutal Colorado winters, and won't give up my OEM battery for any after-market unit.

Lead-acid batteries generally fail when one of the 6 internal cells fail (open). I'm unaware if any internal resistance that builds up - but I'll wager that it's a very minor increase over it's usable life, then a catastrophic failure. It's hard to say if your holier than thou Optima's are plagued with this same problem. I can only assume this is a non-issue. The battery either works, or it doesn't...

You're still missing my point though...I've shown in my previous thread that the internal capacitors in the amplifiers and OEM alternator are enough to support a ~1400 watt system - when cranked...never mind the battery! At this point, the battery is just another filtering device!

The dimming issue is more likely due to the contacts corroding - either at the battery, alternator, ground, etc. This is why I strongly suggest doing the "big 3 upgrade", and using proper wire gauge for ALL stereo components.

I've exhausted my vocabulary from explaining this issue countless ways. If you still feel a Redtop is the holy grail of car audio power solutions, by all means, go waste your money.

 

rocketgyrl..... will you marry me? there needs to be more girls out there that are into cars and car stereos like you are!

 

Nope I never had a Red Top, I have 11 of the Hawker Genises 26ah batteries that I use in my electric vehicles and I have hear of the Reds failing usually from the tightly wrapped plates shorting out. You also should know that the motors I am running are over 90% efficient due to very low internal resistance - in fact if you short out the windings and put a vise grips on the shaft and try to turn it the wires will heat up and it will be very hard to turn the motor - winding resistance is in the milliohms. Yes the standard old car batteries do develop higher internal resistance as they age usually they loose capacity too but not to many people deep cycle them to find out just how quickly they deteriorate. I usually get 10 or more years out of my car batteries without any problems simply by NOT jumping someone elses dead battery with my car or leaving my lights on and running the battery down. Personally I think massive amps in a car are a little crazy and the energy is better spent making the car go - but then again my hearing is very good and I don't need a lot of power to hear music.

You sound like you have an EE degree or spend a lot of time installing amps in cars?

 

HAHAHA...an "e-proposal"? I think more girls (and guys) would be into car audio IF they got to maximize their investment (re: not taking 'bad advice' from the "experts" out there), thus maximizing the performance of their system. Matt will tell you this has caused thousands of his dollars to go down the drain, and no doubt MILLIONS of dollars annually, by everyone getting screwed by bad salesman, bad installers, etc. The internet's proven to be both an awesome tool and a burden to the mobile electronics industry. Matt and I are doing our part online to provide good advice, links to excellent websites, etc. Believe me, he gets just as involved on other forums...


So you've been pushing a product - that you've never owned - to others that you know FAILS regularly??? Then once your buddy's Optima that you suggested he/she get dies, you won't help him/her by giving them a jump? Why would you do that? I need to keep a closer eye on you!

Actually, it's all soaked in from hanging around Matt for 5 years. He's the one with a Masters of Electrical Engineering, specializing in Digital Signal Processing and two Bachelors: EE, and ME. He's been installing systems for 15 years. By day he's an F-16 pilot - by night he's an installer, doing competition level systems. He's opened his own high end shop, Mobile Audio Werks, 4 years ago. The two of us compete with both IASCA and USACi - sound quality. Currently, I'm the World Champion for USACi, and have a bigger trophy than Matt ...probably a big reason he's rebuilding his Audi S4 right now, complete with 12" subwoofers mounted up front, a custom dash, etc.

 

can i come work for this matt?

 

I told Matt about this...he's flattered. He suggested you ,and others that are seeking 'car audio truth' get this book:

http://autosound2000.com/as2k/autoso...fs_thebook.htm

"A2KTB" was written by the "Founding Fathers" of car audio. They've taken a no-nonsense approach to the discovery of car audio. It was written during the late 80's, and early '90s when car audio was in it's prime. It does an excellent job breaking down and explaining all facets of car audio.

Go to as many competitions, IASCA/USACi/MECA - even as a spectator - as you can. These shows have collective best-of-the-best car stereos, installers, etc. Talk to those that are as passionate about car audio as you! Ask them questions about system design, speaker location, tuning, installation, sound damping, etc.

Here's USACi's event calendar:
http://www.soundoff.org/cgi-bin/sche...&display_all=1

IASCAs:
http://www.iasca.com/events/

MECAs:
http://www.mecacaraudio.com/eventtable.aspx

 

I think it's the Red Top ads along the right side of the screen in SL that has been pushing me in that direction. Yellow Tops are more popular for deep cycle use in the EV area - don't have any of those either because the spec on the Genesis batteries are a little better for cyclic use, got a great deal on ebay 5 years ago on them and I love the way they can take a 60 amp charge and be almost full in 45 minutes with just a little heating. Sorry if I questioned your credentials but I had not seen all your other threads.

So to ask a really technical question - do these high powered amps run 12 volts internally or do they boost the voltage with an inverter to get the higher output voltage needed to drive the speakers? Seems you need about 40 volts into a 4 ohm load to peak the power at 400 watts and more if we are talking RMS.

 

Most car audio amplifiers run on 48-75VDC...so yes, there's a switching power supply inside...but that's opening a HUGE can of worms if we go in that direction.

 

Yeah now we start talking about bridge outputs and floating potentials or single ended outputs with capacitor coupled outputs and power up charge surpressor circuits. It does explain the amps ability to handle peak power levels without overloading the battery for a second or two. Bet you are waiting for ISA to become popular so you can start running everything at 42 volts input voltage!

 

^ wow you guys (and gal) are soo on just a new level. lol

 

Yeah - the microscopic level of this stuff can be interesting - like to crimp or solder the ends of heavy conductors carrying high currents. Military wiring calls for air tight crimps with very expensive and specialized tools but I always solder and flow some up the insulation so that all my joints stay cool and conductive even when passing 150 amps for a while. I even use an IR heat probe to check for temperature rise.

 

ummm jan i think ur thread jacking now...hhaha and rocketgyrl i tuned my amp to 500 watts but right now from what ur saying i didnt because i used a test tone cd...anyways im saving for my mag d2 i wanna get

 

How exactly did you tune it to 500 watts? Did you measure the AC output at the speaker terminals, with the speaker playing?

I'm suggesting that IF your amplifier is capable of sustained 600 watts (or even 500- most aren't), that it WILL still reach that amount - but will require a larger input voltage on the RCAs. IF your headunit is the limiting factor ie: it can't produce the required voltage on the RCAs to drive the amplifier to 600 watts, OR if you adjusted the gain **** to disallow the amplifier it's full potential when your headunit is cranked, then your statements would be correct.

 

My amp pushes 1200 Watts to a 12 " Solobaric L7 and with a capacitor I have no dimming issues. (all 4 gauge wiring for both power and ground)