Will this cap work for my car???

eloplayspolo

At more work i get a discount on caps, i can get a 1.0, 1.2, 2, or 5 farad cap, which should i go w/ for my setup? (specs are in my signature)

MacLeod

Not a big fan of caps. Id say youre better off spending the extra cash on a better battery like an Optima Yellow Top or even better, a Kinetic!

eloplayspolo

its about a 100 dollar diffrence, will those work?

Topper

Kinetiks get my vote

MacLeod

The Kinetic is a monster. I was at a show today and a buddy was there that is running a Kinetic 1800. He has a voltmeter on his terminal and with the engine off, it was putt out 13.3 volts! Not to mention the whole 1800 cold cranking amps!!!!

Ya get what you pay for. This is nowhere more true than in electronics.

300m

A cap is just something else for the charging system to deal with. It will help with somewhat smoothing voltage drop, however, it will lower your overall voltage. A cap does not produce power it only stores and discharges it. You are better off upgrading the battery/alternator.

eloplayspolo

i got the 2 farad tsunami cap for 80 bucks, if it doesnt work perfectly ill get the kinetic.

PoweredByDodge

... 80's bucks on a f***** cap, or get a marine battery.

optima, kinetic, etc., are a waste of your money and effort, none of them offer than sizeable increase in reserve capacity over standard lead acid car batteries. a hybrid deep cycle marine battery will provide you will thicker plates and a far greater energy density. after that, cap at 1 farad per 1,000 to 1,200 watts or so. big electrolytic cans are the best for the purpose, the "5 farads in a package the size of a pack of cigarettes" types aren't worth the boxes they're packed in.

my 450 amp hour bank was the best investment of my audio life.



... and why are you running 4 unmatched subs? waste of time and energy (literally).

eloplayspolo

im not running 4 subs.. im running 2 momo 10" SVC

PoweredByDodge

Gotta give it to the car stuff too
- Pioneer DEH-P6800MP w/ I-Pod Adapter
- MTX Thunder Elite Class D Mono 1200w
- MTX Thunder Elite 4-Chan 2100w
- Polk Momo 6.5" Components x2 @ 125W RMS(front Doors, rear deck)
- Polk Momo 10" Single Voice Coil @ 300W RMS x2 (trunk) <

---

- MTX Bass Slammer Dual 10" Sealed <

---

eloplayspolo

Bass Slammer is my enclosure, must have had too many characters, it should say Sealed Enclosure.

PoweredByDodge

MacLeod wrote: »

I was at a show today and a buddy was there that is running a Kinetic 1800. He has a voltmeter on his terminal and with the engine off, it was putt out 13.3 volts!

That's a surface charge.

A 12.6 V battery with 1.8 v cells cannot be 'truly' charged to 13.3 without overcharging it. within a short period of time that surface charge will disappear, and the resulting true state revealed.

13 something is common after you've slammed the battery down low, and then started the car and recharged it for a while... once you're at a full charge and stable, floating it at 13.8 for a while, you can kill the engine, let the battery cool down (they get warm when charging and discharging) and then measure voltage again, i'tll be 12.6.

exalted512

PoweredByDodge wrote: »

... 80's bucks on a f***** cap, or get a marine battery.

optima, kinetic, etc., are a waste of your money and effort, none of them offer than sizeable increase in reserve capacity over standard lead acid car batteries. a hybrid deep cycle marine battery will provide you will thicker plates and a far greater energy density. after that, cap at 1 farad per 1,000 to 1,200 watts or so. big electrolytic cans are the best for the purpose, the "5 farads in a package the size of a pack of cigarettes" types aren't worth the boxes they're packed in.

my 450 amp hour bank was the best investment of my audio life.



... and why are you running 4 unmatched subs? waste of time and energy (literally).

But theyre supposed to have a lot less internal resistance and discharging much faster than your standard batteries...the kinetiks at least.
-Cody

exalted512

I just tested my 1800, its sitting at 12.58V right now, hasnt been running for 8 hours. I have a couple of 2400s sitting in the shop, not hooked up to anything for a few months, ones sitting at 12.8 and ones sitting at 12.75.
-Cody

MacLeod

His car was sitting there running at idle for about an hour waiting to be judged and had been turned off for about an hour when I noticed the reading. So it wont be putting out 13.3 on a regular basis?

And 300M makes the best point against caps. Its just an extra load for your charging system to pull.

exalted512

Actually, Ive heard capacitors dont put a load on the charging system at all...Vince?
-Cody

PoweredByDodge

re - 'car sat for an hour and the juice was still 13.3' -- dunno what to say, assuming he had the lights off, and all the **** in the car was off, then the 13 something charge would remain in the caps, which would then 'float' the batteries at that voltage as well, provided you didn't run anything off of it. as soon as you put a load on it though, it --should-- (notice, should, not 'will') taper down to 12.6 within a minute or so.

re - 'batts in storage and they're sittin at 12.8' -- open circuit, sure. provided the only resistance between the two terminals is air (psuedo-infinity), then a battery that just came off a charger (or alternator - since that's just a charger anyway) and hasn't had any kind of real draw put on it, then it may just sit there in the high 12's without dropping. AGM batteries have a fantastic 'self-discharge' characteristic. unlike standard lead acid batteries (this includes deep cycle and hybrid deeps, like boat batteries or even solar array batteries), AGM's discharge super super super slow as hell with no load. it's one of the many reasons that Optima Yellow tops are reccomended for classic cars or hot rods that don't get driven in the winter... you should still put a 1 amp automatic battery blanket on them, but if you don't there's still a good chance you'll be able to crank that **** over 6 months later.

re - 'less internal resistance' -- bingo. absolutely correct. the lower internal resistance (or 'self-resistance' or 'device resistance') the faster it can charge and the faster it can discharge (power things). However, the energy density is crap. When you're looking to really drive something, then you should be looking for how much power your source can store. A cap can store high voltage (up to 20 V in most cases before you blow it up) but not a lot of current. So even 20 V * 10 amps/minute (that is being EXTREMELY GENEROUS FOR A CAP -- likely 10 times what a typical 1 farad cap can store), is only 200 watts/ minute. A typical group 65 battery, standard lead acid, will give you something like 50A/H * 12.6 V ... so that's 37,800 watts per minute (to break it down to a rediculous scale and compare it to the cap). likely that battery will only be put into service at 200 amps per 15 minutes.

re - 'caps don't put a load on the charging system'. quite the opposite. caps are nothing more than a storage tank... a tiny storage tank. once you empty them, or actually once you drop them down to the same charge level as the battery, then they draw a sick amount of current, over a very very very tiny period of time. if anyone has charged a cap without using a resistor in series with the positive lead, then they know how fast a cap will charge... almost instantly, but it will get quite warm, and you may very well blow your stereo system's power cable main fuse (depends on the size of the fuse, size of the cap, etc). well, you can discharge them just as fast... and then, they will IMMEDIATELY want to recharge themselves... so that current that could have been feeding your amplifier is now feeding your cap.

.... so why bother at all?

Caps are not a power fixer-upper. After a bit of digging, I've found out what caps are actually for in car audio. Took me a few years of thinking the wrong thing to realize it, but, they are not meant to supplement your power source(s). Rather, caps in any power system, are meant to have 2 tasks. 1) stiffen a few tenth's of a volt. 2) counteract the reverse sawtooth 'psuedo feedback' effect of switching power supplies. Open up a big 'ol class D and you'll see a pile of caps inside. often times, they're not enough to negate the 'jiggity' backfeed the power supply has on the vehicle's power system. Hence, cap at 1 farad per 1,000 to 1,200 watts utilized. Energy storage is not for a capacitor... its for a battery. This whole 'oh no, I need to stay at 14.4' **** can be solved really easily...

DE-RATE YOUR AMPLIFIERS!

If you want to run 500 watts to your speaker, then get yourself an amplifier that will put out 500 watts at 12.5 or 12.6 volts, not at 14.4 volts. that way, even if your amplifier draws more current than your alternator can supply, the 12.6 from the battery will still allow you to achieve your 500 watts without changing your gain, changing the volume level on the head unit, or **** with anything. however, IF you have your system tuned and your gains set with the 'key on' (14.4 volts), and your alternator cannot keep up with the draw of your system, then every time you throw that volume level to the roof, you will suffer clipping... you are trying to get 500 watts out of that amp, but it can only do say 350 when its at 12.6 volts, so guess what... flat line at the top and bottom of your sine wave... now you have a real ugly square wave lookin hunk of ****. you're limited by the + and - rails... and if they're only at 12 something due to excessive current draw, then you're not putting out that 500 you wanted, and its muddy as ****.

so... derate, give yourself a pile of headroom, and don't worry about a damn thing. design around 12.6 and call it a day.

eloplayspolo

that was beautiful



On a side note, i got my doors cut, and the momos barley are touching the windows, and w/ the dynamat installed, they will be perfect, SO LUCKY the door panel still fits. Im doing the Final and complete install this wednesday, im stoked and ill post final picks.

exalted512

Still not understanding how a cap is a load. A load is something that uses power, ie headlights, ac, any power that those draw is lost/converted. Like you said, a cap IS a storage tank, all the energy that goes into it is used for those loads, the energy loss in a cap is so small that its almost negligible. Id venture to say you lose more current in the connections to the cap than the cap itself.
-Cody

MacLeod

Right. A cap is a storage tank - guess what fills it up? The charging system. That would be a load/draw/whatever. If youve got an empty 50 gallon drum and you want to fill it up with dirt, well youre going to have to roll your sleeves up and start shovelling.

Am I going to have to make fun of your Aggie education again?

exalted512

No, a cap does not draw anything, the thing attached to the cap draws power. There will be a small amount of loss, but thats almost negligible, especially for car audio. Nothings perfect, for like i said, that energy is almost negligible. Look at the capacitance of a 9V battery, the small ones used in a lot of electronics, theyre generally 5kFarads.
-Cody

PoweredByDodge

a dead cap (or a cap that is at a voltage that is below that of your charging sytem (14.4)) is a load.... it has to gain energy to store in its 'tank'.

conservation of energy dude... juice has to come from somewhere.

example -- cap stores 1 farad at 14.4 volts...

with an ESR+ESL of less than or equal to 0.001 ohms, that gives you an inrush and discharge current of 14.4 / 0.001 = 14,400 amps.

but, an amp is a coulomb per second, and that charge rate doesn't last even one second... so it's more like "a rate of 14,400 amps but only for 1/50th second"

kinda looks like this...



the first red spike is the DRAW current of the capacitor if you just slap it right onto the battery without a series resistance... at time = 1 second, you hook that **** up... notice how it will try to draw almost 15k amps for 100th of a second...

well at time = 2 seconds, you turn on an amplifier...

let's say you're just running this one amplifier that draws 80 amps when putting out its full power. so you're bumpin a 60 hz wave, and you've got you're current draw, that's the blue line.

so the amp hits the note, and it pulls a sick amount of power... the cap tops off the voltage that's been lost due to driving 80 amps through a 4 gauge line (the 0.5 or whatever volt you lose along the way due to the wire's resistance)... and now the note 'ending' (right side of the curve), well the cap needs to recharge, so it's going to pull some proportionate amount of current at a very very high rate (high amperage) for a very small time (hundredth of a second or so).

that's just one note though... play a song, with multiple amplifiers, pulling wicked amounts of current, with a small bank of capacitors, and watch that's thing spike like a ****. the only way to avoid suffering negative effects due to this is to work within your means, and not slap a 300 amp draw on a 100 amp alternator, add an optima and some caps and expect it to be 'just fine'.

PoweredByDodge

ps -- everything except a generator/alternator is a load. batteries are loads, caps are loads, inductors are loads.

exalted512

But how can that be seen as a load? All it does is store energy. The amps draw power and since music is not a single sine wave, it will recharge in 'down' time. Im not talking about using a cap on a honda civic with an amp that draws 200A of current and a factory battery. I'm talking about using caps as load levelers.

Still dont see how its a load if it doesnt USE the current that it draws. All it does it hold it for the next big dip in voltage. Now a battery is different because it uses more power to charge it than you receive in return, still not seeing how a cap is a load.
-Cody

exalted512

"Load-12. Electricity.
a. the power delivered by a generator, motor, power station, or transformer.
b. a device that receives power."
www.dictionary.com

A cap does not receive power, it receives current...
-Cody

PoweredByDodge

re - 'electricity'

---

Cody, dude, seriously, I'm not tryin to mess with you... so don't take this the wrong way...

Don't go all 'Websters' on me without a real good reason, because I don't like it. And I'll respond like this.

--- 'Electricity is a property of certain subatomic particles (e.g. electrons / protons) which couples to electromagnetic fields and causes attractive and repulsive forces between them. Electricity gives rise to one of the four fundamental forces of nature, and is a conserved property of matter that can be quantified.'

That's a far better definition. Electricity is NOT power. It is NOT current. It is all that and more.

Back to your counterpoint though...

Power is current. It is also Voltage. Power = voltage * current, very basic concept. A cap (and a battery) 'receive' (actually they DRAW, because current cannot be 'pushed' into anything) current ANYTIME that they are connected to something that has a higher voltage potential than they do with relation to a common ground.

Hook the negative of a battery and the 'negative' of a generator (the chassis of it) together -- now they share a common ground. Then, if the generator is putting out 10 volts and the battery is at 9 volts, then the battery will draw current from the generator. If the generator is at 9 volts and the battery is at 10 volts, then the battery will NOT draw current.

So... since current is drawn AT a voltage, then the battery is drawing POWER. In this example, 10 volts at whatever amps (lets say 5 for example) -- so 50 watts of power are being drawn, of which, maybe 40 watts will actually be stored in the battery (since most lead-acid batteries have about an 80 to 85% charge efficiency.

But why would a battery draw power? Isn't it meant to deliver power? -- well it draws power when its charging. ((its probably pointless to say that because you know that, but i'm trying to make a point here and it 'fits' with the point)).

So... if a cap, like a battery, is an ENERGY storage device (since nothing on earth actually stores 'power', only ENERGY, which once used, can be called power - the terms are somewhat interchangeable but for this argument it is important to notice that it is energy, since anybody who says 'hey a cap stores power' will certainly be told 'dude, there's no way you're gonna get much power outa that cap, it's just a cap')... if a cap like a battery is an energy storage device, then the cap -- when it is charging -- must also DRAW current to charge up.

You're thinking much to 'black and white' here. If you want to be very very very specific, then I will say it like this...

'Dead' = anything that is at a lower voltage than the main source device (let's say a generator or alternator in this case).
'Charged' = anything that is equal to or above the voltage of the main source device.
((the above disregards what the cell structure of the battery is and what its intended full charge voltage is... this is just a 'imaginary battery' example))

So... a DEAD CAP is a LOAD because it draws current... period.
a CHARGED CAP is a source, because it delivers current... period.
a DEAD BATTERY is a LOAD, same reason, draws current.
a CHARGED BATTERY is a source, same reason, delivers current.

So a cap and a battery can be BOTH a load and a source, depending on their state of charge and what they are connected to.

re - Using current

---

Well... you suggest that a cap (and if we somehow invented a 100% efficient battery, then your argument would have to include batteries as well) does not use power. Since we've covered what power is, we must now change your argument to say that a cap does not use voltage or current... it simply 'stores' them.

Ok, fair enough.

Now you've got to re-think of the word 'use'. Your boss hands you your paycheck... lets say its 1,000 bucks. 100 of it gets USED for bills and gasoline and ****. 400 of it gets USED on fast food, prostitutes, and cocaine (cuz you've been hanging out with me too much and you picked up all my nasty habits) The other 500 you have laying around. So you put it in the BANK (the bank is our metaphor for a capacitor or battery) where you STORE your money.

If you look at it very very very very literally -- very 'absolute, no room for error' like -- then you have to agree that putting your money in the bank is USING it. Because, if you didn't use it, or do something with it, then you would be giving it back to your boss (or, in terms of energy/voltage/current/whatever, you would never actually accept it from your boss).

So, STORING energy is a form of USING energy.

There is also the other kind of 'USE' -- that is, what you normally call using energy... when your amp uses it to pump out music, or when you use it to start your car in the morning, or when you turn your headlights on. We need to call that other use a new name... lets say 'SPENDING' energy... or better yet... EXPENDING energy. Same goes for the money in the bank, eventually you will SPEND it.

So... storing energy is use... and expending energy is use.

I can say this until I'm blue in the face, but the only worthwhile use of a capacitor in the power section of a car audio system is to smooth out power supply kick back (or even a shittily regulated alternator), and to stiffen a few tenths of a volt. they are not, by any means, supposed to load level anything... even something like a 150 amp audio system on a 130 amp alternator... not intended for that use at all, no matter what circuit city tells you..

re - 'it'll recharge in downtime'

---

no it won't. a 'dead' or even 'slightly not full' battery or cap will 'recharge' (or at least begin its recharge cycle) instantly ... as soon as the voltage at the source (generator) is higher than the votlage of the battery or cap, then boom it starts to recharge... you can't control it... it just happnes. it doesn't know that you're playing music. it doesn't say "hey, lets wait until the heavy bass stops and then start to recharge when he's playing celine dion). nope... it just grabs whatever is out there.

re - 'what's a load anyway?'

---

a load is anything with a resistance... whether real or imaginary (real = resistance, imaginary = impedance). anytime this resistance is placed between two different voltage potentials (for example, 10 volts and 5 volts... or 10 volts and ground), then that load will draw current, proportional to the voltage difference divided by the resistance / impedance.

so, if a battery or a cap had zero (0) resistance in a DC system, then it would function as a SHORT, and it would draw infinite current until either a fuse blew or something exploded. So... since a cap has an internal resistance (ESR + ESL) and a battery has an internal resistance (across plates), then they are both loads. if-so-fact-o.

PolkThug

The alternator is where its at.

MacLeod

Allow me to abreviate Vinny's post for easier reading.

PoweredByDodge wrote:

Mac is right.

eloplayspolo

exalted512 wrote: »

"Load-12. Electricity.
a. the power delivered by a generator, motor, power station, or transformer.
b. a device that receives power."
www.dictionary.com

A cap does not receive power, it receives current...
-Cody

i like u .... but what this sad kinda made me chuckle...


electric current
–noun Electricity.
the time rate of flow of electric charge, in the direction that a positive moving charge would take and having magnitude equal to the quantity of charge per unit time: measured in amperes.

PoweredByDodge

... and so we solved it...

--TRANSCRIPT---

(00:27:21) Exalted512: you there?
(00:28:00) poweredbydodgev8: sup
(00:28:06) Exalted512: more about the caps
(00:28:06) Exalted512: lol
(00:28:21) Exalted512: i think a lot of what were arguing is semantics
(00:28:26) Exalted512: lol
(00:28:47) Exalted512: let me reword a question...Will more stress be put on an alternator because it has a cap connected in parallel to it?
(00:29:02) poweredbydodgev8: ok.... much better qeustion
(00:29:06) poweredbydodgev8: two part answer
(00:29:51) poweredbydodgev8: 1) if the load on the alternator (regular load, disregard the cap for a minute -- assume th cap is fully charged) -- if the load on the alt is less than the output capability of the alternator... then no, it will not put more stress on the alt
(00:30:21) poweredbydodgev8: 2) if the load on the alt is equal to or greater than the output capacity of the alternator, then absolutely yes yes yes, it will beat the living **** out of hte alt, you would be better off running the heavy load without the caps
(00:30:58) Exalted512: ok
(00:31:03) Exalted512: thats what i was trying to say
(00:31:08) Exalted512: #1
(00:31:12) poweredbydodgev8: same goes for batteries... if your instantaneous draw (say 50 amps for a 500 watt amplifier) is greater than the 1 hour reserve capacity of your battery... then you're screwed... if its less than, then you can use caps all day
(00:31:15) poweredbydodgev8: gotcha
(00:31:18) poweredbydodgev8: ya... caps are good
(00:31:23) poweredbydodgev8: just gottta use em right
(00:32:03) Exalted512: that if youre using a capacitor to stiffen voltage spikes, then a cap is not a load(by load, i was meaning putting extra stress)
(00:32:21) poweredbydodgev8: if you define a load thatway -- then no, its not extra stress
(00:32:31) Exalted512: thats what i was meaning
(00:32:33) poweredbydodgev8: gotcha
(00:32:44) Exalted512: a load was something that uses power
(00:33:07) Exalted512: cap stores power, doesnt consume it
(00:33:13) poweredbydodgev8: true
(00:33:23) poweredbydodgev8: however... to the alternator -- it doesn't know the difference
(00:33:30) poweredbydodgev8: all the alt knows is that SOMETHING is sucking power off of it
(00:33:45) poweredbydodgev8: alt doesn't care what it is -- just knows its sucking power
(00:34:02) Exalted512: but either way, the alternator is going to be charging
(00:34:08) poweredbydodgev8: so to the alt.. its a load... but in a properly configured system.. then the cap is a source
(00:34:31) Exalted512: and a capacitor charges almost instantly, and if nothing is using that power, itll stay at that voltage
(00:34:42) poweredbydodgev8: yes -- IF nothing is using that power
(00:34:53) poweredbydodgev8: IF something is... then the cap becomes a load
(00:35:23) poweredbydodgev8: because the amplifier has the same reisstance (internal) as the cap - (just about the same) so they're both getting the same charge current -- lets say each gets half of the alternator's output
(00:35:24) Exalted512: but not a load that puts stress occrect?
(00:35:38) Exalted512: correct*
(00:35:41) poweredbydodgev8: so that cap can't charge instnantly since its only getting 40 amps instead of say 500 or 1,000 amps real fast
(00:35:44) poweredbydodgev8: yes... u gotit
(00:36:07) Exalted512: but at that time its not charging, its discharging correct?
(00:36:37) Exalted512: to provide for the current draw from the amplifier
(00:36:48) poweredbydodgev8: in a properly configured system, the cap will spend most of its time doing nothing, jsut sitting there charged... and constnantly discharge little bits of power here and there... and recharge in the 'downtime'
(00:37:16) poweredbydodgev8: in a wrongly setup system... the cap will discharge once in a big amount, and then suck the life out of the alt and batteries trying to recharge
(00:37:54) Exalted512: but even then, is the cap putting EXTRA stress on it?
(00:38:52) poweredbydodgev8: yes, only because of one reason... low resistance of the cap -- because its so low, it can discharge (delivery power) real quick.... but that's also bad because when it wants to charge itself, it tries to charge super fast... so it presents a super super super LOW resistance to the alternator and battery.... literally sucking hte life out of them (stress)
(00:39:07) Exalted512: got ya
(00:39:38) Exalted512: i was talking to an EE at mercedez the other day
(00:39:54) poweredbydodgev8: if the cap wasn't htere, and u discharged u're power system because u're amp sucks lots of juice.... then the alt would just have the constant 'load' of the amplifier -- but with a cap (in a wrongly configured system), then its got the amplifier and its got this really 'heavy load' (low resistance = heavy load) of the cap tyring to recharge

exalted512

Okay, me and Vince have come to a conclusion. We were basically arguing semantics. I was defining a load as something that consumes energy, headlights, ac, anything that you cant get back again, he was saying that a load is anything that uses power...and storing power is using power. I have changed my term from 'load' to 'stress.'

In a properly setup charging system, alternator, battery, and capacitor, a capacitor will NOT pose any extra stress on the alternator and/or battery. It will NOT make the alternator charge more, it will simply stiffen any voltage fluctuations caused by transient spikes in music. It will do what a capacitor is designed to do.

Now in a improperly designed setup, like lets say you have a new accord, running SR components, live in Tennessee, like to lift weights, compete in MECA, have a Raleigh M80, used to own a dodge ram, and have 10 momo subs running off of 4000 watts(thought I was talking about you huh Aaron?) all off your stock battery and alternator, a capacitor will put a tremendous load on your charging system because of one reason... low resistance of the cap -- because its so low, it can discharge (delivery power) real quick.... but that's also bad because when it wants to charge itself, it tries to charge super fast... so it presents a super super super LOW resistance to the alternator and battery.... literally sucking the life out of them (stress)
-Cody