Here are some things I have read that sound good:
"a power capacitor is placed much closer to the amplifiers than the battery is so that voltage drop is going to be much less all other things being equal. But second, your charging system probably isn't designed to provide current draws that large at any time. So your amplifiers are going to have to get the power from the vehicle's battery as well as the alternator. And the battery has its own internal resistance which, as stated before, is much higher than that of a car audio power capacitor. Because of this extra internal resistance it is not an effective means of delivering large amounts of instantaneous current. The capacitor acts like a small tank with a large hose while a battery acts like a large tank with a small hose. So with a capacitor installed you can deliver a large current burst during a music transient and then the capacitor can recharge during the non-peak portions of the music."
"The ESR of a battery is much higher when it's being charged. A battery's natural voltage is about 12 volts. It is at this voltage that it can deliver real current. When it's being charged, its voltage is raised above 12, but it will quickly drop to 12 volts under a load. This is what we refer to as "surface charge."
When the amplifier draws a lot of power the battery can't deliver much current until it drops to 12 volts. That's why the lights flicker much more when the engine is running. The alternator is normally charging at 14.4 volts but when the amp draws a lot of current, the voltage briefly drops to 12. This is because the alternator's regulator is very slow to respond. I guess you could say that the battery isn't in the circuit until the voltage drops to its natural cell voltage."
"The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a tiny fraction of a second, where a battery would take minutes to completely discharge. That's why the electronic flash on a camera uses a capacitor "
"a power capacitor is placed much closer to the amplifiers than the battery is so that voltage drop is going to be much less all other things being equal. But second, your charging system probably isn't designed to provide current draws that large at any time. So your amplifiers are going to have to get the power from the vehicle's battery as well as the alternator. And the battery has its own internal resistance which, as stated before, is much higher than that of a car audio power capacitor. Because of this extra internal resistance it is not an effective means of delivering large amounts of instantaneous current. The capacitor acts like a small tank with a large hose while a battery acts like a large tank with a small hose. So with a capacitor installed you can deliver a large current burst during a music transient and then the capacitor can recharge during the non-peak portions of the music."
"The ESR of a battery is much higher when it's being charged. A battery's natural voltage is about 12 volts. It is at this voltage that it can deliver real current. When it's being charged, its voltage is raised above 12, but it will quickly drop to 12 volts under a load. This is what we refer to as "surface charge."
When the amplifier draws a lot of power the battery can't deliver much current until it drops to 12 volts. That's why the lights flicker much more when the engine is running. The alternator is normally charging at 14.4 volts but when the amp draws a lot of current, the voltage briefly drops to 12. This is because the alternator's regulator is very slow to respond. I guess you could say that the battery isn't in the circuit until the voltage drops to its natural cell voltage."
"The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a tiny fraction of a second, where a battery would take minutes to completely discharge. That's why the electronic flash on a camera uses a capacitor "
You can not even buy a stiffening capacitor from the retailer at which I work. It did not take us long to figure out that it was not doing anything to help the dimming headlight problems that people were purchasing them for. In order to remain a reputable shop, we refuse to sell them. So now if a customer comes in and requests a capacitor for their system we are installing, we try the best we can to convince them that the cap is going to do nothing to rectify the dimming headlights they are concerned with. Their answer is always the same, they must work, my boy has one and his lights do not dim at all. Then they ask, if I go get one will you install it. Of course we say yes. They leave and come back an hour later, proudly toting the cap in one hand and the lighter wallet in their pants pocket. We install it and then they get mad at us because their lights are dimming. Come to find out, their boy has 2 10s on a 400 watt amp and we just put 2 3000 watt amps on his 6 13.5s.
I have told the boss we should get some for the ones that insist we sell them one, she refuses to knowingly help them throw their money away.
I have told the boss we should get some for the ones that insist we sell them one, she refuses to knowingly help them throw their money away.
I had one successful implementation of a capacitor in my 1996 Thunderbird, and it was for an issue that was NOT advertised. I installed it to get rid of a noise problem that had several other installers as well as myself baffled. After I put the capacitor in my system, the noise went away.
A friend of mine from here, who moved out to California when he joined the service actually recommended the cap to solve the problem! IIRC a huge capacitor can filter out high frequency noise, but I never understood why the filtering caps in the amp couldn't handle that duty
A friend of mine from here, who moved out to California when he joined the service actually recommended the cap to solve the problem! IIRC a huge capacitor can filter out high frequency noise, but I never understood why the filtering caps in the amp couldn't handle that duty
Seems obvious to me a typical cap holds a tiny amount of power. If you need that tiny amount of power for an instant to fill in a lag, then sure it will work for that purpose. So if you are right on the edge of capacity it may help, just seems most are way over what the car can produce so it is not going to help that. It will filter too, and I've been told it can help lifespan of other electronics in the car as well as alternators. I agree its not going to do that much. Seems proper use for power issues is to get a huge alternator and huge bank of caps, then you can run 14.4v solid long as the caps cover the regulator lag and you don't overdraw what that alternator puts out. Aside from that you just need more battery to keep from dropping under 12v, if you don't go the big alternator route or play it with car off.
Would be great if someone could give more detail how a cap might affect other electronics in the car or the voltage regulator. I was told on an amp hit it would drain the input caps of anything in the car and a large cap on the amp might help it not do that so much. I got a 1f for $15 I will try, I figure it can't hurt. But also I am not running that much power likely will stay under 600-800rms total and I think I have a 125A alternator. I get a slight pulse in lights without one, but not bad. I fail to see how a cap could hurt, though it may not be worth the money you could use for other improvements.
Would be great if someone could give more detail how a cap might affect other electronics in the car or the voltage regulator. I was told on an amp hit it would drain the input caps of anything in the car and a large cap on the amp might help it not do that so much. I got a 1f for $15 I will try, I figure it can't hurt. But also I am not running that much power likely will stay under 600-800rms total and I think I have a 125A alternator. I get a slight pulse in lights without one, but not bad. I fail to see how a cap could hurt, though it may not be worth the money you could use for other improvements.
I think this is a key problem. People don't seem to understand that *ALL* of that power,has to come from the alternator.Once the car is started,it's not running on the battery anymore,the alternator is supplying all the power for the car. The battery will come into play if you draw a large load,and the voltage dips..the battery will 'buffer' it. A cap does something similar,but on a smaller,faster scale.
A cap does *NOTHING* if your alternator cannot support the load.
The bottom line is: Your alternator must be able to supply the current needed by everything. *THAT* should be your first upgrade.
Well said and SO true. I have seen car battery's dip to 8 volts on heavy load as they are SLOW to meet the demand also, and cold they are even slower. Or they are just being loaded beyond there rating so badly that they drop output trying to supply current.
Some alternators are also slow, and all have High Temp current limiting inside then as built in protection for the diodes and such. And there output is Shaft Speed dependent. If its not turning enough RPM then its just not capable of handling the load also. Hence the use of smaller over-drive pulleys to rev up the shaft speed at idle. But this adds limitation on high RPM speed also.
Adding a properly spec'ed cap can improve noise issue somewhat, and can buffer the slow responding charging system and battery, and help out a little bit on many of these things. But its not a properly engineered solution unless all of these facts and data are put together to get a clear overall picture of where the problem is. Some things need to be directly addressed before anyone should even think about adding a cap system.
BUT most people just have no idea how all this stuff works and what the variables are and how they effect the overall performance of the charging system, and eventually the car audio system. Hence the "Bad Bandaid Rap" Caps have.
Dealers spend X time building up a system in a car and never even look at weather the car can actually handle the load that is getting installed. It reminds me of a picture I had sent to me of a donkey cart tipped backwards lifting the Donkey into the air. Funny how stuff like that happens. Sell 10 Grand of car gear and install it on a car that can barely keep its head lights on when running...lol lol lol Seen it a million time it seems like over the years ..lol lol lol and everytime I see that poor Donkey in mid-air in my mind ...Lol lol lol
When doing the SPL thing I was able to get a DB or 2 after installing a cap bank....and I had (11) 1000 cca batteries and 4 alts.
We did only play our "music" for a few tents of a second....not really real world anything!
IMO with new class D amps makes even less sense to run caps unless you are going back to 1990 in a time machine.
~JH
We did only play our "music" for a few tents of a second....not really real world anything!
IMO with new class D amps makes even less sense to run caps unless you are going back to 1990 in a time machine.
~JH
Class D amps draw even more power then the old AB amps did nowadays. They are just more efficient at using that power and getting it to the speaker load.
So I kind of disagree on this point as with the advent of D class amps came even higher demands on systems. You must admit there are more Kilo-watt based systems out there now because of D class power. And the car charging systems still only have a minimal margin of extra reserve especially when you look at all the extras new cars have like Electrically heated seats, Navigation, DVD, Computer engine control, Window defoggers, High intensity turn aiming halide head lamps...etc...
Modern cars are loaded up even more then ever straight from the factory, Then you add a high end aftermarket audio/video system...Well I think you get the picture.
Plus please remember car makers only just barely build a charging system capable of running the car and all of its accessory's, with maybe a 500 watt safety margin. If that, So adding even class D amps requires a rethink of how much is possible without redesigning the charging system for the application. Car makers also run Minimal wire size in ALL modern cars trying to keep Curb weight down and gas mileage up and emissions down. I just had to unload my truck to get it smogged, Weight is a serious issue with car makers nowadays, and huge copper wires are weight just like thick windshields < all of which are things of the past nowadays>
Another point of view to take on this is that it is the Car Audio Industry's Dirty little secret that NO car built by any company has the margins needed in its stock design to allow such upgrades. Perhaps this is why they back the lowly 1 farad cap the way they did, or perhaps it was the 85% profit margin they were making. Either way the aftermarket equipment makers don't want to publicly mount a campaign of truth and honesty when it comes to weather there equipment can be run in a car without spending loads of cash under the hood to make it functional.. just something to think about when looking as to the why's and how's of this question concerning big Caps.
I have a Golden rule I like to use to explain things to people that can barely change the oil in there car on a timely basis, and it goes like this:
I never could work in sales in this business, maybe knowing the technical truth has always been my problem, along with having a conscience
Or maybe it was seeing the poor Donkey hanging in mid-air that bothered me the most LOL LOL LOL ...
I'm going to mildly disagree with some of the above information.
The battery's natural state of charge, ie...fully charged, is 12.6 volts. A battery at 12 volts is 50% discharged. "Surface charge" is the voltage you read off a battery that has been charging but has not yet dissipated the surface charge on it's plates from the charging procedure. The actual state of charge can be determined by a volt meter after the battery has sat for 15-20 minutes.
The alternator's charging voltage of 14.5-15 volts can be read with the engine running but it is not indicative of the battery's state of charge. Often the answer to the problem of rapidly discharging a battery is the installation of a larger alternator. I would submit, for the purposes of car audio, that the larger alternator does more to prevent excessive discharge of the battery than it does for actual charging, though for our purposes that may be sufficient in and of itself. But a larger alternator is not the answer to a chronically discharged battery. The problem with the alternator is that it does not charge the battery in a linear way.
A battery at 12 volts, 50% discharged, may well take all of the output of the alternator in charging voltage. But as the battery charges it will accept progressively less of the charging voltage. An alternator running continuously will actually supply about half it's rated amperage during charging, ie...a 60 amp alt. delivers about 30 amps, without over-heating.
If the voltage regulator is set at 14.4 volts, that alternator will deliver 30 amps to a 50% discharged battery, about 14 amps to a 25% discharged battery, and only 2 amps to a fully charged battery. This reflects the "acceptance" rate of the battery; as it charges it accepts less and less amperage. You can cram the first 50% of the charge in there in about 1/4 the time it takes to charge the last 50%. Continuously discharging the battery, stressing it, will result in sulphated cells and shortened battery life. Best to keep the battery near full charge if possible.
Auto batteries have a lot of thin lead plates in them while deep cycle batteries have fewer, thicker plates. Auto batteries release, and accept, their charge more quickly as reflected in their high cold-cranking amps, while deep cycle batteries discharge more slowly while retaining more amp-hours of reserve power. A deep cycle battery may not surrender enough of it's power quickly enough to crank your car over, due to the relatively low surface area of it's lead plates. But, if you can fit it, a larger deep cycle battery may give you enough cranking amps while maintaining it's inherently greater reserve capacity. Absent the ability to fit a larger sized battery I recommend that, for a given size battery, you buy the heaviest one that you can. More weight equals more lead and more exposed lead for discharge/charge.
In my opinion, capacitors are fine for that extra oomph needed to crank over an electric motor but I'm a bit at a loss as to their benefit for an audio system requiring rather periodic, and often, needs for extra oomph. With capacitors it's a bit of a zero sum game. Use their amps and you have to immediately replace their amps. If you're cranking Jeff Beck's "Love Stinks" when is that going to happen?
The best answer, in my opinion, is more battery. Maybe even before more alternator. (I'd recommend the same type, size, and construction of battery as what you're already using, for charging considerations that would involve a more lengthy conversation. If you're going to throw an AGM in the trunk, put one in that is the same size AGM you just placed in the engine bay.) The extra storage capacity will not only utilize more of your alternator's capacity but will also provide a cushion during high amp draws. And you'll avoid the deep discharge that is the killer of batteries.
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