What kind of cap/amp?

**GoHybrid** · 12-24-2006, 12:04 AM

yeah. i've read through it. it validates your arguments at the expense of excluding practically all evidence that would lend credence to the idea of using a capacitor in your car.

Also, i've seen several of your posts on the matter to other users and they are usually terse and unhelpful. I understand it gets tedious explaining yourself over and over again, but if that's what you believe then at least give these new guys the benefit of the doubt and link them to your evidence, but I assure you there is more to the issue than you let on.

Lets remember the basic electrical power relationships. When your amps start to lose voltage, they do two things: 1. draw more current to compensate and they 2. start to distort the signal, build up heat, and potentially shut down or fail.

Lets also remember the things that cause voltage drops:

1. excessive current draw. (long term)
2. insufficient wire size to those loads. (indefinite term)
3. turn-on surges. (short term)

Perhaps because of the proliferation of all manner of cheap and poorly designed amplifiers, and the ridiculous amounts of power they claim to make, whether peak or RMS, excessive current draw is a common problem in car audio systems. Based on this, I can see why the assumption is made that the amplifier is causing a gross over-draw situation in most cars.

Shadow, MegaloRESE15", here is where I support you:

if your alternator is incapable of creating enough current at common engine speeds (idle/cruise) to supply the current demands of your amplifier, you are SOL until you upgrade your alternator. Voltage drop because of insufficient wire size, which is technically relevant to the gains realized by the Big 3 may add up to a few amps, but if your import alternator is only making 60 amps hot and that oversized monstrosity of an amp in your trunk has 4 25A fuses... don't expect to get much out of that setup, even with bigger wires. CAPACITORS WILL NOT HELP HERE: Because now not only does the underpowering alternator have to contend with the big amplifier, but it's got a draw at a depleted capacitor to deal with as well.

Lastly... you're rolling to a stop and hit your brakes, and lights dim? Well, you've got alot of factors working against you: turn on surge from the brake lights can be sometimes as high as 2-3 times it's nominal current, the internal capacitance of your amp is almost certainly being taxed and/or depleted and your alternator is not keeping up. The most obvious symptom of this is dimming lights. Turn on a flashlight with dead batteries and you'll see the effects of reduced voltage on a light.

Now HERE is where i fill in the blanks that I so frequently see left to the imagination:

I have NEVER seen anyone ask in a capacitor discussion about the total application. Never, "do you drive an import car? big truck?". Sometimes those factors can mean the difference between a 60A alternator and a 120A alternator. Please see above for why this is important. Your brake lights, auxiliary lights, signal lighting (especially), pc power supply, can all exhibit turn-on surges that exceed the alternator's current supply threshold and cause dimming of lights. a capacitor as typically installed will not only supply power to your amp, but also to everything else mentioned. Since those surges are measured in milliseconds and everything else is just gravy for sometimes seconds at a time in between, a capacitor would be PERFECT to solve the dimming problem because it has plenty of time to recharge and only has to handle the intermittent pulses of current draw until the alternator speeds up and supplies a total surplus of current again.

Not to mention it can be done potentially easier and almost certainly cheaper than a new alternator. As mentioned by others, additional batteries are potentially cheaper yet, but require more space, weigh more, and need to stay charged, especially in cold weather to remain effective. Using a second battery in parallel, particularly in absence of smart charging circuitry will require more current and more time per volt than a single battery, thus it's less likely that your alternator will be able to meet those requirements versus the requirements of charging a capacitor.

So in closing, let me say to those of you considering a capacitor for your car: there is more to this decision than just "will it give me more bass or stop my lights from dimming?". You have to analyze your whole system and it's power needs and decide based on that what the most cost-effective decision is. Get clamp-style DC ammeter and hook it to your ALT+ wire in various conditions (lights on/off, stereo cranked, turn signals on/off, defrosters etc...) and get a baseline reading. Check your main power cable to your audio/pc system. Do you see which is supplying more power than the other?

Bottom line: it's never as cut and dried as you think. Do ALL the research and look at BOTH sides of the issue and somewhere in between is a solid answer.

/rant off.

**Jahntassa** · 12-24-2006, 12:33 AM

To the OP. I have a Tsunami Cap in my wife's car. Honestly? It's the same as pretty much every other cap. It just has pretty flashing lights.

I also have a Cap in my car.

Why do I have Caps? Here's my reasoning. I didn't upgrade the alternators, but I did upgrade the grounds under the hood. In my car, I have 4Ga running everywhere from the battery. THAT, helped. Having real solid grounds under the hood instead of the stock 12ga to the bumper helped a LOT.

Unfortunately, my problem comes in at IDLE with the headlights on. This is the ONLY time anything in my car dims. My headlights take a LOT of power.

And y'know what, the Cap helped soften that. At least as far as the subs (on tight, frequent notes) would drag down the system. Is it a perfect solution? No. But, I know people who have upgraded alternators that STILL had a problem of lights dimming at IDLE.

My car is fine when it's at speed (2k rpm or higher), so if i'm moving, I wouldn't need the cap. I only have the cap to soften the blows when i'm sitting still.

I have no scientific data. I don't claim to be intelligent, i'm just stating my situation and what I did. Is it a band-aid? Maybe. Am I guaranteed that a higher-output alternator would fix my problem at Idle? Not really.

That's just me.

**GoHybrid** · 12-24-2006, 01:18 AM

that's all just real-world proof of concept about what I'm saying. As far as alternators go, it's really a very tweakable thing. Just like a supercharger you can use a smaller pulley to make it spin faster and generate more current at idle engine speeds. The flip side of that is that your regulator and thermal management solutions need to be able to handle the even higher speeds it's going to encounter when the engine is revving. Based on some preliminary research I've done, it seems that Iraggi alternators have an extremely high output at idle (amputator series, 180A max, 130idle). That sort of thing could solve alot of problems for alot of people. It's also ~$500 fully warranted. You can get caps for quite a bit less to bring things a little closer to ideal (as jahntassa said) for considerably less money.

**Megalomaniac** · 12-24-2006, 10:03 PM

my iraggi has a 115a at idle and 200a on a higher rpm. I had a choice to get the 65a on idle but i decided to step my game up a bit with the higher current on idle, best choice i made. my lights will dim only at the lower notes, but i can solve the problem with an extra battery, right now i only have a yellow top under the hood...yes i am pulling quite a bit of power.(around 1200watts from the NINe1 and 170watts for the frontstage, plus around 60-80watts for the carputer...and etc for various other things like headlights and ac.) a 2nd battery should help MY situation.

**treetop777** · 12-24-2006, 10:18 PM

Originally Posted by MegaloRESE15"

my iraggi has a 115a at idle and 200a on a higher rpm. I had a choice to get the 65a on idle but i decided to step my game up a bit with the higher current on idle, best choice i made. my lights will dim only at the lower notes, but i can solve the problem with an extra battery, right now i only have a yellow top under the hood...yes i am pulling quite a bit of power.(around 1200watts from the NINe1 and 170watts for the frontstage, plus around 60-80watts for the carputer...and etc for various other things like headlights and ac.) a 2nd battery should help MY situation.

Then in your case, assuming your big 3 are optimized, a cap would also be a viable solution..right?

**Megalomaniac** · 12-24-2006, 10:22 PM

my opinion: hellz no, a 2nd battery will be more benificial.

**GoHybrid** · 12-25-2006, 03:05 AM

I think the thing to do in megalorese15"'s case would be to figure out WHY he is pulling more than 115A at idle, and why that power isn't being supplemented properly. That's an awful lot of power. But here's a consideration: his battery is at fault. If all he has is a yellow top then that may be the problem right there. Yellow top batteries are deep cycle batteries. That means they are mean to sustain a lower current draw for an extended period of time, particularly without the application of a charger (hence "deep" cycle). If he is exceeding his alternator's output capacity and is counting on more power in a hurry from his battery, then a yellow top is the wrong place to look. Red tops are FAR more appropriate for the kind of multipurpose applications we subject our starter batteries to. The point is that Red tops are constructed in such a way that they can supply INSANE amounts of current at 0 degrees in an instant for say... starting a cold motor? As it turns out, this is exactly what he would need for his situation. Sudden high current draw = use the correct battery. If that didn't solve the problem itself, then what he ought to do next is consider an appropriately sized capacitor. Their quick charge/discharge times far surpass that of any battery and frankly, that is his dimming problem. Not enough amperage the instant he needs it.

Granted, an additional battery connected in parallel will have the same effect as using the right battery to begin with, but then he can further complicate matters by having to make sure that he doesn't exacerbate the problem by suddenly having to charge TWO deep cycle batteries at 15+ amps a piece for the entire duration of his journey.

In my opinion, he spent all that money on a fine alternator and he ought to consider both alternatives and use that power efficiently rather than just band-aiding the problem with more batteries.

i might also add that the correct use of yellow tops would be to power a sound system for competition or while the car is off. In this case you would use as many yellow tops in parallel as you needed to be able to supply the instant current demands, plus as many as you need to be able to achieve the run time desired. Bear in mind though, charging many batteries like that requires sophisticated chargers and above all... lots and LOTS of current.

**Megalomaniac** · 12-25-2006, 03:48 AM

I did and still compete in spl compettions now and then. The burps drain a lot of power. but I comepeted USACi outlaw style. so alty did take a large role for the good.
I thought about investing in a redtop for under the hood and have the yellow in the trunk linked together in paralel. But don't know too much about what batteries to use. Here's what do I know. the yellow tops are deep cycle and are usually meant for the "accessory" load. the deep cycle part is the bateery can be drained and recharged several times without damgin battery life. I'm not too sure what the marine "bluetop" is used for besides boats, but I've seen ppl use them in cars. now I did thought about using a Kinetik 2400 for a trunk battery since it has a current capacity than a g31 yellow top. advice will be appreciated. but please I am very hard headed about caps so don't mention them. I might consider a batcap.

**treetop777** · 12-25-2006, 12:55 PM

Originally Posted by GoHybrid

If that didn't solve the problem itself, then what he ought to do next is consider an appropriately sized capacitor. Their quick charge/discharge times far surpass that of any battery and frankly, that is his dimming problem. Not enough amperage the instant he needs it.

The above is what i learned from this thread..there is no definite "ALWAYS get a cap" or a cap is NEVER needed" answer..Thank you.

**GoHybrid** · 12-25-2006, 01:24 PM

okay, speaking strictly batteries now:

With regards to battery construction there are some subtle differences between a deep-cycle and starter battery that significantly affect their performance.

The basic reaction is between the electrolyte and the lead plates that comprise each cell of the battery. One of the effects of this reaction is a degradation of the lead plates, particularly following a deep discharge (80%) cycle. This is sometimes referred to as sulfation.

A starter battery has many thin plates, sometimes with hole patterns in them to increase the surface area of the plates. The more lead plate in contact with acid, the more reactions you get, and thus more current. This means that you can have a smaller battery give more power very quickly. Because the plates are so thin though, the effects of that degradation are more pronounced and can quickly diminish the capacity of the battery to perform. Since your alternator can supply adequate charging current, this should not be a problem since you can start reversing that reaction the second it occurs and can leave the battery in a high state of charge. Just don't run your stereo with the engine off.

Deep cycle batteries use much thicker, and therefore heavier plates. As a result a battery of the same size cannot supply as much current. The thickness of the plates however allows this kind of battery to tolerate deep discharges better than starter batteries. Bottom line... there's just more fresh lead there to work with. This makes the battery suitable for extended discharges with no replenishing current available. So if you wanted to run your system with the engine off, i'd find a way to isolate your starter battery (should be a red top) and link multiple yellow tops in parallel to be able to collectively supply the momentary loads your system creates.

Alternatively, you CAN get a deep cycle battery with the same current delivery capacity as a starter battery, but it will likely not fit in your existing battery tray. So if you were one of those people who relocated their battery to the trunk and just used one or two group sizes UP, then you could use a deep cycle battery as your starter/standby battery as well. But that's more work...

Here's another thing to remember: The harder you pull on a battery, the lower it's reserve capacity gets. A battery with a drain of 1 amp for 20 hours is going to hold out better than a 20 amp drain for 1 hour. So it is best to spread your load across as many batteries as is feasible for your application... assuming you don't care about adding 100lbs a piece to your car and want the best run time.

if you're willing to consider a "batcap" then you're willing to consider a capacitor. That's what it is. search for "ultracapacitor" on wikipedia and you'll probably find some examples of these in the 500-2600 farad range. They even mention that this type of capacitor is used for temporary power during battery replacement.... so you can imagine how long these things can hold up to a load. The differences between this and a battery are vast, but the neat thing is that some of these higher rated units can fully charge in about 10 seconds. Show me a lead-acid battery that can charge that quickly and I'll show you a customer that needs about 6 pallets of them.

BTW: merry christmas everyone!