In my experiences, many newbies think they need a capacitor installed along with their amplifier and subwoofers because of the reason that a capacitor will provide power when the amp needs it. Here’s the problem: When bass is playing, the amp always needs power, and whatever “extra” power it needs will be sucked out of your capacitor in a few seconds max. After you have discharged the capacitor due to heavy power draw, the capacitor will need to recharge.
How does it recharge? Well, the capacitor sits in between your alternator/battery and your amplifier. Once the capacitor is discharged, it will attempt to charge itself by drawing power from your electrical system. The power that could just pass from your electrical system directly to your amplifier now has to pass through a capacitor before it reaches the amplifier. Then, once the amplifier needs power again, the vicious cycle starts all over.
Most common car audio capacitors are rated at 1 farad, while I’ve seen some reach as high as 5, 10, 20, and higher. No matter how high the rating, a capacitor will still hamper performance. This is because capacitors cannot supply the needed current for any extended duration of time to a high power amplifier. When your amplifier needs current, it will suck the capacitor dry in a few seconds (usually less), leaving your capacitor to call on your electrical system to charge up.
See where I’m going now? If a capacitor can only hold a charge for a few seconds, while drawing substantial amounts of current from your electrical system in an attempt to charge back up, all while delaying power the amplifier, then what is the point? There is none. What makes that setup better than giving your amplifier direct access to the alternator/battery? In comparison, imagine two of the same cars driving in two separate. One lane is smooth to the finish and the other lane has a speed bump. Everything constant, the car with the smooth lane will reach its destination before the car in the speed bump lane.
Capacitors are known in the car audio comity as a marketing ploy to make people think they need something, when in reality, they really don’t. Take your money and invest it in a second battery. A capacitor these days runs between $50-$80. Add a few more dollars and you can get a second battery, which will supply your amplifier with much more power than a capacitor ever could, all while not straining your electrical system. A Kinetik HC600 is a prime example of a supplementary, inexpensive battery and some searching puts it in the $80-$110 range.
And for the guys who insist that capacitors work, that’s probably because they probably don’t have large amplifiers. Here’s a really good explanation as to why capacitors may “work” for them. I say “work” because people say capacitors “work” based on the fact that their headlights aren’t dimming as much. This article is meant for people with larger systems, say over 1000W RMS at the least.
More links:
BCAE1.com – capacitors
Does a “Stiffening Capacitor” behave like it does?
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I have a one farad capacitor and with the way it is hooked up the amp takes power from the battery unless a really hard bass note hits that the battery/alternator can’t handle, then it will take what it needs from the capacitor. during the time the amp isn’t takeing it from the capacitor the capacitor can charge, at least that is how I understand it. If not the capacitor drains extremely quickley but it only needs that power for a second because once it is going it is easier to sustain.
You don’t understand the purpose of the capacitor. It is not there to provide power. It is there to give a quick kick to the amplifier when the deep bass notes sound – it discharges more quickly than a battery can, and then recharges almost immediately. Without it, you will tend to overdraw your vehicle electrical system when the bass notes sound. You will see this as a dimming of your lights when the bass notes sound.
Mark, that’s the exact misconception people have about capacitors.
“The amp always needs power, and whatever “extra” power it needs will be sucked out of your capacitor in milliseconds. After you have discharged the capacitor due to heavy power draw, the capacitor will need to recharge.”
The capacitor is yet another link between your the positive battery terminal and the amplifier input. Since the capacitor cannot keep charged, it draws from the battery, then the amp must draw from the capacitor. The amp should be drawing directly from the battery with no interference. A powerful system (above 2000 wrms) would probably be hampered more than helped with a capacitor. Even lower power systems may suffer as well.
You must misunderstand the way you connect the cap then.
The cap isn’t between the battery and the amp, it is on it’s own circuit, grounded to the frame.
It provides another source of power for the amp to draw when a high powered bass note takes the power normally going to the lights and such, thus prevents the lights from dimming.
So then . . . how does the cap provide a “source of power for the amp to draw” if it’s on it’s “own circuit” and “isn’t between the battery and the amp”?
Eric, Caps do drain quickly. But if you get one rated for your output, it will not drain right to empty. Infact, if it does ever drain right to empty then it becomes a short, in the system and the cap will run the risk of exploding.
see this site: http://www.carstereo.com/help/elect_upgrade.cfm
Amps only need the power in a capacitor for fractions of a second and can provide power for more than one second. Amps do always need power but they don’t always need excesive power. Only when the wave reaches it’s peak. I’m sure your familure with a sign wave? Only at the peaks on each end of the wave will a cap be required because that’s when the strongest draw is placed on the system. Car batteries are better at constant draw, not quick bursts. That is why a cap will help with sound quality, not hurt it. Amps have capacitors built inside them. The only time caps are a bad thing are when you don’t have the proper cap for the job.
What you say may be true and benefit people with low power systems; I’m aiming towards the competitor/serious enthusiast. And with systems of that caliber, you cannot find a large enough cap for your output, neither would you want to use one if you could. Quoted from the website you provided, for the serious enthusiast, this is basically why capacitors are a waste of money:
“Capacitors might help, but they do not take care of the fact that your car’s system is underpowered. They are a “patch” for a more serious problem”
And when you’re pushing multiple thousands of watts, you’ll need a very large, hundreds of farads capacitor. You don’t find those too often and if you did, they’ll probably be hundreds of dollars. Those hundreds of dollars could be better spent on more batteries.
Amps might only power from the capacitor for a fraction of a second if there are say, some quick bass hits, but what about long, low bass lines or sine waves? That would suck a cap dry (not dry, but force it to recharge via the battery), which is bad.
“Only when the wave reaches it’s peak. I’m sure your familure with a sign wave? Only at the peaks on each end of the wave will a cap be required because that’s when the strongest draw is placed on the system. ”
All sine waves reach a peak. Are you trying to say that the amp doesn’t need a capacitor’s power unless there’s a “peak” sine wave? In that case, there are peak sine waves in every bit of music and the amp will need to draw power from the capacitor 100% of the time. If you’re trying to say that the amp doesn’t draw from the capacitor unless you turn it all the way up, then that defies the laws of physics. How can the amp draw straight from the battery when the capacitor is in bewteen?
And lastly, it’s not a case of latency (e.g. how fast the capacitor can get power to the amp vs the battery) because the difference between the two are VERY minimal. Sure, a cap may be .01ns faster at delivering power to the amp than a battery, but 1) no way in hell you’ll notice that difference and 2) it’s the power capacity that’s important, of which a battery holds vastly more of.
What in the dickens? I was led to believe caps would help harmful drains on alternator and electrical systems, is this not the case? I am adding one to my boat, that has a single 1000w amp powering 2 subs and 8 speakers, I already have good wiring and 2 batteries, I just didn’t want to strain the alternator any more than I had to. I also don’t like wasting money on gimmicks. >:(
Capacitor or not, you’ll see be putting an equal amount of strain on the alternator. The amp has to get its juice somehow, either from your two batteries which charge off the alternator, or from a capacitor, which is connected to your two batteries, which are connected to your alternator. So, it all goes back to your alternator. 2 batteries should be sufficient enough for a 1000w amp. What is your alternator’s output rated at? My Honda Accord alt is rated at 90 amps, but I had no problem powering a 3000w+ amp with two batteries and a stock alt.
“And when you’re pushing multiple thousands of watts, you’ll need a very large, hundreds of farads capacitor.” the commen rule is that a farad is good enough to 1000watts so a ten farad cap is good enough for 10,000 watts why would you need hundreds of farads for any thousands of wattage people with 10,000 watt amps or 2×5000 amps will not be on this site and will know enough to not ask this question
Did you to read what I wrote right after that? “Those hundreds of dollars could be better spent on more batteries.” That’s the moral of this whole article – money is better spent on batteries rather than capacitors.
The common rule you speak of is pretty widespread and BS. Again, yes, it will work for puny systems, but once you get up there in power, the rule no longer applies. If you think 1 farad per 1000watts will be sufficient enough for a 3 second sine wave, you’re dead wrong. I’ve seen it fail in competition and you will rarely find anybody using capacitors, especially the higher up guys. The only one’s you do see using capacitors are the idiots who bought into the marketing. These idiots are also the one’s that think that their Kicker L7′s “are the shiznit yo”.
And yes, of course people running multiple thousands of watts will know this already. This is for people that don’t know, which there are a lot of.
I”ve NEVER heard of high powered systems using caps, (imo they are a ripoff) especially in the comps, where they use batteries in multiples of like, 10.
Well just an FYI, amplifiers are made of capacitors. if you ever open up your amplifier you will see many little capacitors.
LOOK HERE:
http://image.ec21.com/co/f/fswudong/img/oimg_GC00233542_CA01627203.jpg
THE 4 big cylinders in the middle going vertically are capacitors.
The 9 verticals ones on the right are capacitors
the 4 on the left going horizontally are capacitors.
A few thoughts from an electrical engineer:
The capacitors for car stereo applications are used to reduce the ripple, or variations in voltage, which in turn allows the amplifier to produce its rated output. An electrolytic capacitor like the ones used for car stereos can release energy rapidly as well as charge rapidly. They do not store anywhere near as much energy as a lead acid battery.
Now your power cables from your battery to your amp have a fixed rating and can deliver a fixed amount of current (due to losses and voltage drop due to resistance – simple I2R losses)
So if you want to supply a CONSTANT load the capacitor is useless. However when the load is VARYING the capacitor can charge during periods of low load by using the excess capacity of the power cable and during periods of high load the capacitor will release its energy into the load. So the load will receive the power transmitted via the cable as well as the power available in the capacitor.
The largest factor here is the type of music that will be fed into the power amplifier. For rock and the like with long bass transients a capacitor will have little effect since the amplifier will be drawing a reasonably constant current, and the capacitor will not be able to recharge. However for music like “doof doof” with short peaks of heavy bass the power drawn by the amplifier is varying and hence a capacitor can help in certain situations.
What sort of situation could a capacitor be useful? Well obviously your choice of music will have to be as described above “doof doof” or similar. Secondly your cable from your battery to your amp and capacitor setup would be underrated for the maximum peak output of the amplifier but not smaller than the maximum average (over say 5 seconds) of the power drawn by the amplifier.
As you can see this is not that common, however a capacitor will not degrade the system, so if you wanted to add one cause you felt like spending money that’s fine. However the obvious solution in most cases would be to reduce the resistance in your length of cable (either by increasing the size or reducing its length to its point of supply), or install a battery in close proximity to your amplifiers (or vice versa).
Capacitors can also be added in parallel to increase their combined capacity.
As you can see a serious competitor will usually use extremely large cable, or add additional batteries in close proximity to the amps (which would be fully charged before the competition), however not everyone can do this and in certain conditions the use of a capacitor in a properly designed system is a good design decision.
Finally if you expect to supply your amplifiers for extended periods of time then your power generating capacity must be at least equal to the power drawn. ie if you have a 10,000W peak, 1500W average, system and only a 85A alternator then your battery will be drained over a period of time (simple kirchoffs current law)
WOW! Thanks for the huge, detailed explanation, Paul. Totally agreed on the constant load. Music isn’t constant, but tones (sine waves) are. Competitors with high power systems at competitions will only play tones while being metered and a capacitor just won’t cut it. Maybe if we had a flux capacitor
Eric, I agree with the overall message of your article – Capacitors are a waste of money for car audio systems. However, some of your points are just plain wrong (in the opinion of another electrical engineer):
“If you’re trying to say that the amp doesn’t draw from the capacitor unless you turn it all the way up, then that defies the laws of physics. How can the amp draw straight from the battery when the capacitor is in between?”
Wrong!
Capacitors are connected in parallel with the battery and the amp – I trust you are familiar with the differences with series and parallel circuits?
The purpose of the capacitor is to ‘support’ the battery voltage during transient periods of large current draw.
During normal operation the capacitor will charge to the alternator output voltage – which is higher than the battery voltage.
If the alternator voltage is stable, the capacitor will sit there and do nothing.
When the combination of music type and volume cause the current draw on the alternator to be higher than its rating, a voltage drop will occur.
If this voltage drop is transient in nature, the capacitor will certainly be able to supply the required power to prop up the voltage.
This however doesn’t mean that a capacitor is a good design decision
A capacitor is simply masking the fact that the alternator can’t supply enough power to the amp.
The most cost effective method to improve the performance of a car audio system is to upgrade the wiring – particularly “the big 3″
(Refer http://www.isyougeekedup.com/the-big-3-car-audio-wiring-upgrade/)
Next best thing is to upgrade to a larger or deep cycle battery (this may cost more than a cheap capacitor, however it is actually addressing the problem, not masking it)
Overall I think that capacitors are only popular for the “bling” factor
They have fancy flashing lights and they contribute directly to the ‘fully sick-ness’ of any system
why not just get a batcap?
I know my comment is late but I have to agree with Eric. I have a 1,500 watt kicker amp bridged to to kicker L5′s and a 1,600 watt kicker amp bridge to my highs, and a capacitor. The capacitor was a waste of money because I practically have to get a new battery every year. I saw a new one today and it was nice and shiny and built like a battery but it was $300 bucks. I was going to get it until i read this article and now I changed my mind and just going to get an extra battery.
Interesting to see these arguments as this is something I’ve also wondered about, and I’m just about to put about 1800WRMS worth of amps in my car.
In my previous car I had a 1F cap installed with just a small 4CH amp (I think 300WRMS), and I can’t say I noticed any difference in audio quality, but I do have to say that there was a the usual benefits of the various lights not going dim to the music. The car did seem to perform a little better (EFI), but I don’t have any proof of that, apart from the car starting quicker.
I agree that the solution to getting more power should come from the top down, with the top being the alternator, then batteries and cables; but the original article lead me to believe that it was assumed the capacitor would be connected in series… not a good idea for the exact reason that was in the article. If the cap was hooked up in parallel, you should get a constant supply from the battery regardless of what the cap is doing. The amp should only draw the excess that the cap has stored and will only reduce it to a point that is equivalent to the supply from the battery.
With all that said and done, I still am not convinced either way, but I do know that another battery won’t fit in the BMW, and as a matter of cost, another battery for me here in Australia costs the same as a 30F cap sent from the US, and that doesn’t include the cost of getting a dual battery isolator/solenoid setup…
YOU GUYS ARE STUPID…..
Capacitor is pretty much a battery , ITS WAY WAY LIGHTER , but has a better energy to weight storage ratio. The reason why a capacitor is needed is to give quick needs for energy since capacitor charge and discharge rapidly , which batteries charge and discharge slowly. Each has their benefits.
But putting a capacitor in your vehicle for your sound system is completely a stupid idea unless your a millionaire , and in its own circuit, is a dumb fucking idea of understanding of electricity. Your capacitor whenever its drained has recharge in order to supply the energy for the system. Ok so how can you recharge it without energy from the alternator.
Completely stupid reasoning , Now if your rich you could get a big enough size supercapacitor that holds more energy than a battery. Replace your battery and use that to run your system.
This way your alternator is still doing the same amount of work , with less inefficiencies of multiple transfers and storing of energy. Thus having you with a more net gain in power transfer for your system.
That is only if you have alot of money , better budget spending if your not as worried about weight , is to have another battery , and or a beefier alternator.
It all comes down to energy transfer. Better alternator without major modifications of having a shitload of batteries to power your system for a long time , why not have it run off of just the fuel and not fuel and stored energy from the battery and still drain the battery but longer time to do so since theres so much already stored energy.
Just get you a beefier alternator , and have the battery rating or capactior in order to meet the energy restoring demand..
Interesting to read different opinions about how all this works.
After reading all posts this is my summary and decision:
1. Install all your audio components and test it at night.
2. If the lights of your car dim go get a cap.
3. If the lights does not dim at all, put 20 bucks per month in a jar to get a new battery in 12 months.
Good luck to you all !
WASSSUPPPPPPPPPPPPPPPPPPPP BREDRANS.
well I dont know everything about electricity but I have a 12 inch w7 in my trunk and a 1000 watt 1 channel amp, battery always died, put a 2nd optima battery that was being charged from the alternator (split from car battery) along with a cap and it was giving nice clean smooth bass for hours while driving, cap finally blew out or something cause battery always died, so some guy took cap out and put amp form 2nd battery to the sub no cap, now it works but the qualioty sucks ass its a vibration instead of a thump went back and he said I need a 16v battery or a new cap, 16v batterys are 400 dollars caps are about 150, i guess a new cap for me, any suggestions?
The thing is, people get confused in the real purpose of a cap. A cap is not used to, cure or prevent dimming lights, change the way the system sounds, save the battery/alternator (all are misconceptions).
To undertsand the purpose you need to understand how they work.
A cap does it’s best to keep the voltage at a certain level, but if the voltage changes so will the cap voltage. The cap just makes the change smoother. The diming light syndrome is caused by a sudden current drop due to lack of current supply. The voltage simply follows what the current does. A cap cannot help this situation nor can it provide more power. A cap only gives what it gets.
A cap is perfect for a noisy voltage line. This is why caps are used in AC to DC power supplies as they are used to smooth out the DC ripple for a more smooth DC output.
The ONLY cure for dimming lights is a more hefty amperage source, the alternator.
The REAL powerplant of the car is the alternator. The ONLY purpose of the battery is to start the car and run the accessories with the engine off, nothing else.
A.A.S. degree in Electronics/Industrial Electronics with 25 years in the mobile audio/consumer electronics field
Oh and a cap NEVER discharges when connected to a power source. There can NEVER be a difference in voltage between the cap and the supply. If there is, it’s not connected right.
A cap can never hurt your system, thus it is never a waste or a bad idea. It is a reservoir of power for when the amps need bursts like heavy bass hits.
This author Eric is wrong, and this is because he doesn’t understand how electricity works.
Author is assuming the cap is between the battery and the stereo, this is not the case. There is a distribution cap that you connect the wire from the battery to, then from there you have your amps wired to it, as well as the capacitor. What this does is puts the capacitor closer to the amps than the battery. When the amps draw voltage, they pull from the capacitor because it is closer. The capacitor refills from the alternator. If the capacitor was empty, the electricity would just flow straight through the distribution cap to the battery, bypassing the capacitor circuit. There is no “speed bump” and the analogy only makes sense if you wired up your stereo wrong. Use a distribution cap, put the capacitor on it’s own circruit, and don’t listen to this fool talk about things he doesn’t understand.
Here’s another article explaining how car audio capacitors work:
http://www.installercentral.com/tech-tips/2009/04/17/tech-tip-does-a-%E2%80%9Cstiffening-capacitor%E2%80%9D-behave-like-you-think-it-does/
And some quotes:
For systems drawing lots of power, this is not good news.
You know I am in electronics right now as my major and I gotta say I liked what the engineers had to say. Now in Eric’s case, I get what your saying: get a battery instead of capacitor; I personally agree, and that’s because as previously stated batteries have more juice.
I think what it all boils down to is to each his own and that’s because not everyone will want a battery and not everyone will want a capacitor. I personally believe extra batteries are the way to go, that’s because they fill the need that I have for extra juice. If I liked capacitors for my needs I would say go with them, how ever I don’t.
In the end go with what you feel comfortable with, that’s what I would suggest. Nobody can tell anybody that they are wrong for going with what they feel works, just make sure you make an informed decision before you go out and buy something you might regret spending money on; battery or capacitor.
Love, Peace, and Chicken Grease
The author of this is all wrong, go back to school, you dont seem to understand power at all, you missed the whole point and its ludicrous the way you defend your point.
The Cap maintains your system power at higher than battery voltage when there is a momentary higher current draw. Caps are used all over the friggin place for this same reason. There are caps in all of your electronics to condition power.
You amp is rated for 14.4V, not battery voltage.
Caps are good for competition, they make like 200 farad caps, maybe not that high when originally posted. Regardless the cap will help.
Yes, having another battery is nice, but when you already have a 1000 cranking amps battery what is another going to add, although for little tiny cars may have an issue here. No one said to add a cap to compensate for an alternator not big enough. These are power fundamentals, you have to have it all.
I have a cap because I know how it works. I also put in a 150 amp alternator instead of my 100 amp alternator, and yes I have 3 batteries, and my truck has 2 stock. The extra battery has nothing to do with performance, just longevity at a drive in or outdoor event without starting the truck.
A great way to buy car audio on a budget is to buy used equipment
THIS IS A GOOD ARGUMENT HOWEVER YOU PROBABLY DO NOT UNDERSTAND HOW A CAPACITOR WORKS (NOT JUST THE ONE IN YOUR CAR)…A CAPACITOR MAY BE DRAWN IN A CIRCUIT DIAGRAM AS BEING IN BETWEEN THE TWO TERMINALS IN THE CIRCUIT HOWEVER THAT IS JUST FOR ILLUSTRATION PURPOSES AND THAT IS NOT HOW IT REALLY WORKS…IF A CAPACITOR IS REMOVED FROM A CIRCUIT THE CIRCUIT WILL NOT BECOME OPEN…THAT IS WHY ANY CAPACITOR, EVEN IN THE CAR ONLY HAS ONE POSITIVE TERMINAL…THEREFORE THE CAP IS NOT BETWEEN THE BATTERY AND THE AMPLIFIER BUT REALLY ACTS AS A SECOND SOUCE OF POWER TO SUPPLY THE AMPLIFIER WITH SHORT BURST OF EXTRA POWER WHEN IT IS NEEDED SO THAT YOUR MUSIC DOES NOT DIE DOWN OR THE SYSTEM JUST FAILS TO PLAY THOSE REALLY GREAT BASS NOTES THAT WOULD REQUIRE THAT EXTRA BIT OF JUICE =) ESPECIALLY IN HIGH POWERED SYSTEMS…PROVIDED YOU HAVE AN UP GRADED ALT AND A NON STOCK BATTERY IF YOU ARE PULLING ALOT OF POWER….
ALSO CAPACITORS ARE NOT INTENDED TO PREVENT THE LIGHTS FROM DIMMING OR PREVENTING ANY OTHER SYMPTOM OF A “NOT BIG ENOUGH” POWER SUPPLY EXCEPT FOR THE REASON I STATED ABOVE. IF YOU DO HAVE A REALLY LOW POWERED SYSTEM THIS WOULD BE THE ONLY REASON THAT THE CAP MAY HELP YOUR DIMMING LIGHTS…ALSO THE CAP WOULD PUT EVEN MORE OF A STRAIN ON YOUR ALTERNATOR SO IF IT IS A STOCK ONE AND YOU HAVE A MODERATELY HIGH POWERED SYSTEM( USE YOUR DISCRETION) THEN PLAN ON SOME ALTERNATOR TROUBLE IN THE NEAR FUTURE.
CAPACITORS DO WORK AND ARE VERY USEFUL IF YOU WANT GOOD QUALITY BASS AND DONT WANT TO MISS THOSE SPINE TINGLING, HAIR ROOT VIBRATING LOW BASS NOTES. HOWEVER ALOT OF PEOPLE HAVE ALOT OF MISCONCEPTIONS ABOUT THE USES OF A CAPACITOR AND SO IF YOU GET A CAP FOR ANY ONE OF THOSE MANY REASONS THEN YOU CAN LISTEN TO ERIC AND JUST DONT WASTE YOUR TIME AND MONEY BECAUSE IT IS NOT GOING TO WORK FOR YOU IN THE WAY THAT YOU INTEND.
for me upgrade the alternator in to a highest current to feed all the needs of a car’s electical accesories as well as the the audio system…. rewire the auio system in proper wire size then put the appropriate capacitor in series to the battery and amplipier… no need to install an extra battery because its occupies space in a car, expensive and easy to damage rather than a capacitor…thanks!- larry cera of philippines
Spend money or steal your neighbors battery every year…..what ever happend to a regular am/fm radio with mono speaker in the dash.
You got to have a fr@#kin degree for this sh@#!!!