How to Tell if Power Cap is Bad

maka78 · Post by **maka78** » Tue Sep 16, 2008 12:54 pm

So I'm in the process of re-doing my sound system (as you can probably tell from my million questions on this forum - and thank you to all that have answered, this forum has been a real big help!) and was wondering if I should replace my TI Powercore. For some reason, I don't think that thing works - is there a way to tell if it's working?

When I turn on my radio, I can hear the relay click on and my lights dim a second. Other than that, IDK if it's really doing much. Although this might not be the cap's problem, I did have headlight dimming with 2 TI400.2s (100x2 @ 4 Ohms) and a TI800.1 (800x1@2 Ohms) at full volume. I have a 185 Amp alternator in there and a regular battery. I figured the cap should make up for the battery and I wouldn't need a yellow top.

The other thing I haven't checked is that I do believe I might have a weak ground (I just slapped the ground somewhere not real tight), so that's why I don't think the light dimming is related to the capacitor being bad - just want to know how to check out the cap though.

Sorry for the long winded question.

Post by **stipud** » Tue Sep 16, 2008 1:03 pm

Capacitors weren't made to solve lights dimming. They are designed to filter out A/C ripple from the D/C voltage inputs. AKA noise entering on the power leads due to poor alternator regulation.

#1 cause of dimming lights is clipping. Do you have bass boost on? How have you set your gains?

Post by **smgreen20** » Tue Sep 16, 2008 1:50 pm

stipud wrote: #1 cause of dimming lights is clipping.

Do tell.

No.1 cause is not enough power in the cars electrical system.

Caps are bandaids. Underneath it the cut is still there. The cars elec system still has to charge the bank of caps. Just as it would have to w/a 2nd battery. Caps came about for that cheap way for instant power. They can discharge power and charge faster then a battery that's also how it cleans up the DC power.

Just had to give you a hard time Tom.

Post by **stipud** » Tue Sep 16, 2008 3:51 pm

Of course! But with a 185 amp alternator I do not think he is running out of power with his amps, unless he listens to test tones all day maybe?

Clipping will cause the current draw of the amp to rise significantly. This is why heavily bass-boosted cars will tend to flash more. I have never seen a gain matched amp cause excessive headlight dimming, even on a stock alternator.

Maka, who supplied your alternator? Do you know its idle current output? Many of the high amperage aftermarket units barely achieve stock output current at idle.

deathcloud · Post by **deathcloud** » Tue Sep 16, 2008 4:04 pm

So your telling me that my lights are dimming due to the fact that my amps are clipping? I have a 400.2 and a rsd600.1 and do not really have the gains that high. wierd. I always thought it needed a cap to help so when the bass hits it can have enough power.

Post by **stipud** » Tue Sep 16, 2008 4:22 pm

deathcloud wrote:So your telling me that my lights are dimming due to the fact that my amps are clipping? I have a 400.2 and a rsd600.1 and do not really have the gains that high. wierd. I always thought it needed a cap to help so when the bass hits it can have enough power.

Capacitors do not help with this at all. They are an A/C ripple filter, which improves the SQ of your amp. They are not a bandaid for clipping or insufficient power!

Please read the gain setting tutorial:
http://phoenixphorum.com/gain-setting-w ... vt280.html

Also, make sure your power system is adequate. This includes ensuring your grounds are well sanded, and that you have at the very least upgraded your battery ground up front to the same gauge as the wire going to the back!

Post by **Jacampb2** » Tue Sep 16, 2008 4:31 pm

Lights dimming does not automatically mean that the amps are clipping. Granted that the current draw is going to be in a nearly worst case scenario during clipping, and will cause the lights to dim, but there are other factors that can cause excess current draw w/o the amp being driven to clipping.

One big one would be poor connections. Corroded or loose power and ground connections would be high on my list, especially if the amp is theoretically set up correctly. Corroded power connections are high resistance connections, that means that more current has to be drawn to make the same amount of power. The same goes for your ground. Both the amplifier ground to the chassis, and the battery ground to the chassis. A loose connection arcs, as it arc the connection pits and gets covered in carbon, the more it happens, the worse it gets until the resistance is very high and current becomes excessive. Eventually something will give, and it will destroy the amps power supply, or catch the wiring on fire, or hopefully, just pop a fuse if it is properly fused.

It is also entirely possible to drive an amp into clipping regardless of the position of the gains. If you have a head unit or line driver capable of producing more than the maximum voltage that the amplifier can accept at the inputs, then you can drive amp into clipping even with the gain set all of the way toward it's minimum setting. An example would be an amp rated to take a maximum of 4V on the inputs being driven with a 8v line driver making it's full 8V.

To the OP, the first thing I would take care of, is the "ground that you just slapped somewhere, and not very tight" and see where that gets you.

Later,
Jason

Post by **Jacampb2** » Tue Sep 16, 2008 5:10 pm

stipud wrote:Capacitors do not help with this at all. They are an A/C ripple filter, which improves the SQ of your amp. They are not a bandaid for clipping or insufficient power!

I am not trying to start a debate, but this is not entirely true. Capacitors do filter AC ripple from DC and that is their primary purpose when used in a DC circuit, however, I think the confusion lies in the semantics. Look at it this way, the reason the lights dim is because there is a voltage drop when there is a high current draw. Provided that the voltage returns to its original level once the current draw decreases (song ends, or the bass quits hitting, or you turn it down) then this voltage sag is AC ripple. The textbook definition of a capacitor used in a DC circuit, is "a device which opposes a change in voltage" it doesn't matter whether the voltage change is a high transient, or a sag, the capacitor will try to maintain the voltage to which is was charged. It acts almost like a resistance to change. How much change it can resist ultimately depends on how much energy it can store, and its ESR which limits how fast it can react to the change. So, all the BS out of the way, a power supply cap does have it's place. If, and this is a big if, the charging system is capable of supplying the overall demand, then a capacitor of appropriate size should help reduce the effects of high current demand during musical transients.

The problem lies in the fact that a lot of people think a capacitor will fix problems when they have a 95a alternator and 3000 watts of amplifier power on tap. This is simply not the case. The voltage has to be able to recover back to it's normal level in order for a capacitor to have a beneficial effect. How quickly it has to recover all depends on how large the cap is, but keep in mind we are talking about microseconds, or in some cases, milliseconds, not seconds, or minutes of help. I fully agree, that a charging system capable of supplying the maximum current necessary is imperative. Even the best alternator voltage regulators cannot respond to change as fast as even a mediocre capacitor placed near the distribution to the amplifiers.

Long story short, a PS or stiffening capacitor is beneficial, but only if the rest of the power supply is up to the task.

Later,
Jason

Post by **stipud** » Tue Sep 16, 2008 8:14 pm

Thanks Jason. We are on the exact same page. You just put it more eloquently

Post by **Jacampb2** » Tue Sep 16, 2008 9:27 pm

stipud wrote:Thanks Jason. We are on the exact same page. You just put it more eloquently

I knew that we were, but as is typical with complex questions/answers, almost everyone looks at things in a bit different light. I see quite often on the web that ~stiffening caps are useless~ and although the short answer is normally 100% spot on for the folks that are asking the questions, it isn't true for everyone.

I tend to think that we are a more elite crowd here, and that at least means that those that don't have a more firm grasp on things shouldn't be given a chance to learn. They are after all on the finest ever manufacturers fan site

I'm also bored at work, on another graveyard 12hr-- I tend to get chatty

Later,
J

Post by **fuzzysnuggleduck** » Tue Sep 16, 2008 10:02 pm

I wanted to read more about capacitors so I was doing some searching on google and ran across this:

http://www.autoaccessorystore.com/home_ ... wizard=&s=

It claims to deliver 400A at 12V for 8 seconds sustained in what looks to be the half the size of a car battery, or less. Opinions?

Not to hijack the thread or anything...

Post by **mhyde71** » Tue Sep 16, 2008 10:20 pm

wanna see hear more, as I think and feel my wiring and power is sufficient, but still get dimming..
Have done Big 3, decent cap (alumpro 5f Black), 0ga all around up to distro and clean clean connections, fused at distro block, and recently blew one fuse in the MS275, and lights have dimmed from jump street... HAVE HO Maniac Motors Alt (200a or 190a)... SPV1170 Stinger Batt... why would lights still dim...

Just got the alumapro cap... when I threw juice to it.. it sparked for like a straight 3/4 seconds to a tapering down.. before puttinfg it in, i put voltage meter to it to see if any charge on it.. was told that the black caps do not need any type of resistors, or relays juicing it up or keeping it juiced?? spoke to alumapro about that - they confirmed, but do not recall them saying that you'll get fireworks when connecting power to it???

any help/suggestions are welcome and alway appreciated.

bretti_kivi · Post by **bretti_kivi** » Tue Sep 16, 2008 10:53 pm

you got fireworks because it wasn't charged and sucked as much as possible in as short a time as possible.

If you have dimming problems with a reasonable alternator, I'd suggest a second battery on a split-charge circuit. If there's still issues, then something else isn't right.

Bret

Post by **mhyde71** » Tue Sep 16, 2008 10:56 pm

bretti_kivi wrote:you got fireworks because it wasn't charged and sucked as much as possible in as short a time as possible.

If you have dimming problems with a reasonable alternator, I'd suggest a second battery on a split-charge circuit. If there's still issues, then something else isn't right.

Bret

okay cool beans.. i appreciate it.. may give it a whirl...
any suggestions for good second battery?? what about those batcaps??? anything there? or shall I grab like another stinger or something??

gkitching · Post by **gkitching** » Wed Sep 17, 2008 5:22 am

Check out Kinetik.

www.kinetikpower.com

Post by **stipud** » Wed Sep 17, 2008 6:16 am

Have you set your gains with a DMM Matt? If you are popping fuses on your amps, they are definitely getting stressed out over something!

maka78 · Post by **maka78** » Wed Sep 17, 2008 6:29 am

wow, this topic definitely blew up since I posted it yesterday - glad I put up a topic worth discussing and can help more than just me

.

As for my light dimming problems, the more I read, the more I think it's my ground connections. I have 0/1 GA running from the battery to the PowerCore, and a 4 GA running from the PowerCore to a ground. I think this should be replaced by a 0/1 GA. Secondly, I never replaced the battery ground stock cable.

As far as my amps clipping, I have always set them with a DMM and sine wave signal, with no bass boost, so I don't think that's the problem.

This leads to a follow up question - I'm gonna end up running around 3400w RMS overall, do I need a 15F PowerCore capacitor, or is this overkill? I've been told in the past that 1000w = 1F, so I should be fine with a 3.5F cap - true/false? As far as battery, I am putting 1 YellowTop as my main battery, and that's it (besides having the 185A alt).

BTW - 185A produces like 90A at idle, but 185A at 1500 RPM, which is normal for most aftermarket alts.

Post by **mhyde71** » Wed Sep 17, 2008 6:29 am

stipud wrote:Have you set your gains with a DMM Matt? If you are popping fuses on your amps, they are definitely getting stressed out over something!

no I certainly havent, would love to though.. I am completely ignorant as to how, what, etc.. in respect to that??? All I have is a voltage meter, measures ohms, voltage, etc... $7.99 at radio shack.. do i use one of those, or is it something else...

I dunno what DMM is.. HELP!

but yeah it was one of the smaller 10a fuses inside the amp itself.. that blew.. happened once before on opposing 275, and that was due to running the speakers w/o tweeter in the loop and causing/potentially presenting a lower ohm to the amp. still worked (in both cases) but just sounded like C-R-A-P.

maka78 · Post by **maka78** » Wed Sep 17, 2008 6:38 am

mhyde71 wrote:
no I certainly havent, would love to though.. I am completely ignorant as to how, what, etc.. in respect to that??? All I have is a voltage meter, measures ohms, voltage, etc... $7.99 at radio shack.. do i use one of those, or is it something else... I dunno what DMM is.. HELP!

DMM = Digital MultiMeter = what you got for 7.99 at radio shack

A short description is: Unscrew the wires going from your amp to your speakers, and put the red/black DMM wires in their place. Turn car on and put in a Sine Wave CD, turn head unit volume to 3/4 of max. Look at voltmeter and adjust the gain until you get a specific number. The number you're looking for is sqrt(P*R).

Example: 200w going to a 4 ohm speaker -> 200*4 = 800, sqrt(800) = 28.28. Your voltmeter would read 28.28 V when properly set.

Keep in mind that different media play at different volumes. For instance, if you set this with a CD, your IPod plays a lot louder (as in my radio's case), so you can't put the HU volume up to 3/4 like you did when testing. Basically, you have to still go by ear after you set your gains properly, but at least you have a baseline of where you should be.

More detailed information here: http://phoenixphorum.com/gain-setting-w ... vt280.html

Test tones here: http://www.soundbuggy.com/Eric/Test%20Tones/index.html (thanks stipud)

Post by **mhyde71** » Wed Sep 17, 2008 6:47 am

very good, And I take it I test with meter with just like th elower voltage setting (i.e. 20V or 200V, or whatever it is..) it is DC current or AC from there?? I will play out the ms2250 i have and post it up so you can have a look at it for me.. and see if i really do have it...

We're not thread jacking are we on all this.. sometimes things just blow up from things like this

maka78 · Post by **maka78** » Wed Sep 17, 2008 6:58 am

into amp is DC, out of amp to speakers is AC voltage

Post by **stipud** » Wed Sep 17, 2008 7:51 am

Alright Matt... so let's say you've got an MS2250 playing 500x2 at 2 ohms stereo.

Temporarily disable your EQ, and make sure your crossover is at least above 60Hz (ideally though, bypass it). Unhook your speakers. Play a 60Hz test tone on repeat. Turn the deck up to 3/4 or so, to make sure it's not clipping (this will be your MAX volume from now on!). If you have any line drivers, or EQs, you need to set their gains FIRST! Always work down the chain from your headunit.

So if you have a linedriver with 8 volts output, you can unplug the output RCAs and put the + lead of your multimeter in the hole, and touch the - lead to the RCA shield. Then you would adjust the gains until you hit 8 volts OR the clipping light starts to flash. My Audiocontrol Four.1 EQ claims to put out 8 volts, but the clipping light would go crazy above 5... so I would leave it there.

For the MS2250...
V = sqrt(I * W)
V = sqrt(2 ohms * 500 watts)
V = 31.6 volts

So now measure on one channel, and increase the gains until you read as close to 31.6 volts as possible. Bam! You're done. Hook everything back up and away you go!

I must admit though, I do not gain match my subwoofer amplification like this. I only do it for my regular speakers. On my subwoofer amp, I have my gains set higher, and use an LPL to lower the volume. So the very bottom of my LPL is gain matched, and anything above that increases the sensitivity. So on music with a quiet bassline, you can increase the sensitivity of the sub amp to add some more bottom end. You have to be VERY careful to not induce clipping this way, so make sure you turn it down BEFORE you put on a bassy track.

In a perfect world we would all have oscilloscopes. In this case you hook it up and increase the gains until you see visible clipping, then you turn it back until it becomes clean again. Easy! Too bad Oscilloscopes are so expensive

KHPower · Post by **KHPower** » Wed Sep 17, 2008 6:14 pm

Great topic! I use a 5 farad cap bank to keep everything clean and it also works great for a distribution block.

i was feeding 7.88 volts to the ZX500 and noticed my headlights and interior lights dimming up like crazy and I guess the 7.88volts going to it was making it clip. It doest sound like clipping but I guess it is.

I thought that Phoenix Gold's tech said all there amps can handle a 8 volt load????????

oyvind · Post by **oyvind** » Wed Sep 17, 2008 6:16 pm

Since this topic started as a capacitor discussion, here is another question.

1 large capacitor or several small in paralelle?

I want to add som capacitors to my system. In the old days (1998) the discussion was if a 1 farad capacitor could release the power fast enough to make a difference. Has there been an conclusion to that discussion? Will two 0.5 farad capacitors in paralelle be any faster? They are a bit more expensive than the 1 farads. I have done my homework and

By the way, whats up with the price difference between all the different brands of 1 farad capacitors? Isn't a capacitor a capacitor?

maka78 · Post by **maka78** » Thu Sep 18, 2008 6:39 am

KHPower wrote:Great topic! I use a 5 farad cap bank to keep everything clean and it also works great for a distribution block.

i was feeding 7.88 volts to the ZX500 and noticed my headlights and interior lights dimming up like crazy and I guess the 7.88volts going to it was making it clip. It doest sound like clipping but I guess it is.

I thought that Phoenix Gold's tech said all there amps can handle a 8 volt load????????

'

When you say 7.88V, you mean input volts from the HU to the amp?

How to Tell if Power Cap is Bad

How to Tell if Power Cap is Bad

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