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Old 01-16-2011   #26
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Default Re: Capacitor Myth

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Originally Posted by stream View Post
More info please.
It's just as simple as I said it: everybody knows Optima and I bet caraudio-dealers get a nice quote on them, so a lot of people use them and everybody thinks it's because they're the best...
Fact is an Optima Yellow Top becomes nothing more than chemical waste after you discharged it completely a few times, just like an ordinary liquid acid battery...

There are plenty of batteries on the market that are not only cheaper, but also withstand discharging completely better, discharge slower when not in use, have a lower internal resistance causing a better and faster maximum peak-current delivery...

We have here an Exide Maxxima Deep Cycle for example. Costs a bit less than a comparable Optima, but won't die after a couple complete discharges.
I've had this battery standing around for almost 3 years after the previous project, without any maintenance-charging, just standing there...
3 years later, I needed it, so I brought it to the guy that always fixes my Car to hang it on his professional battery charger for a few days and asked him to do measurements and tests on it since it wasn't used for so long...
The result: it still performed better than the specs said!!!

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Old 01-16-2011   #27
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Default Re: Capacitor Myth

Capacitors have some great uses.

Capacitors are NOT for letting you put in a "bigger system". Capacitors do not give you more energy. Capacitors will not give you more "watts".

A Capacitor is great for allowing a 4 channel amp to have instant access to all the Power it needs, and for cleaning up the Power generated by your alternator. Capacitors are also nice for helping to negate light dimming from using your windows, etc. while listening to your music. A big capacitor can be a good thing, and when used as a SUPPLEMENT, its a valuable piece of equipment.

If your amp pulls 200A and your Car only has a 110A alternator, a cap will not help you. In fact, it might make your problem worse. If your Car has an ailing alternator, and you have recently started to get light dimming from it, a capacitor will not help you and will help kill your alternator faster.

As an aside, I'm an EE here too. Wish i could get a nice internship at a power utility, I'd love to get a job in a power plant. Nice stable and high paying work there.

I couldn't imagine going through EE school to just be an electrician. The money's just not in the same league, and it's a whole lot of time spent for no reason. I can understand wanting to be more hands on (I'm the same way), but man, I just don't think I could make that same decision. EE is 5 years pretty much country wide now, that's a lot of time to get into something that's not what you graduated in.
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Old 01-16-2011   #28
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Smile Re: Capacitor Myth

Quote:
Originally Posted by FAUEE View Post
Capacitors have some great uses.

Capacitors are NOT for letting you put in a "bigger system". Capacitors do not give you more energy. Capacitors will not give you more "watts".

A Capacitor is great for allowing a 4 channel amp to have instant access to all the Power it needs, and for cleaning up the Power generated by your alternator. Capacitors are also nice for helping to negate light dimming from using your windows, etc. while listening to your music. A big capacitor can be a good thing, and when used as a SUPPLEMENT, its a valuable piece of equipment.

If your amp pulls 200A and your Car only has a 110A alternator, a cap will not help you. In fact, it might make your problem worse. If your Car has an ailing alternator, and you have recently started to get light dimming from it, a capacitor will not help you and will help kill your alternator faster.

As an aside, I'm an EE here too. Wish i could get a nice internship at a power utility, I'd love to get a job in a power plant. Nice stable and high paying work there.

I couldn't imagine going through EE school to just be an electrician. The money's just not in the same league, and it's a whole lot of time spent for no reason. I can understand wanting to be more hands on (I'm the same way), but man, I just don't think I could make that same decision. EE is 5 years pretty much country wide now, that's a lot of time to get into something that's not what you graduated in.

Actually the money is there if you are motivated. My Union Wireman make an average of $75k/yr. As a contractor/owner I pull in after overhead/expenses between 200k and 250k. I could NEVER make that working strictly as an EE. And with my degree and experience I don't have to hire EEs to design for me. It's a win win for me and I get to truly enjoy my work and get out in the dirt with my boys.

PS:

"Just an Electrician" isn't a very nice thing to say. The IBEW Union apprenticeship is 5 years of school and 8000 hrs of OJT just to qualify to take your Journeyman exam. I did the entire 5 years of apprenticeship as well as my time at Berkeley. IBEW Union wireman are some of the best trained Commercial/Industrial Electricians in the world. 300+ apply every yr just for the opportunity to enter the apprenticeship... maybe 20-25 a year are let in. So being "Just and electrician" is an understatement in my opinion.

Working on an install plan for my 2013 Subaru Legacy. Will post a build log soon!

Last edited by FartinInTheTub; 01-16-2011 at 10:49 AM..
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Old 01-16-2011   #29
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Default Re: Capacitor Myth

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Originally Posted by FartinInTheTub View Post
Actually the money is there if you are motivated. My Union Wireman make an average of $75k/yr. As a contractor/owner I pull in after overhead/expenses between 200k and 250k. I could NEVER make that working strictly as an EE. And with my degree and experience I don't have to hire EEs to design for me. It's a win win for me and I get to truly enjoy my work and get out in the dirt with my boys.
Ah see that makes sense there, if you can combine being an EE and an electrician, there's definitely money there. Vertical monopolies are a beautiful thing.

A guy in my classes was a union electrician, but he got downsized with the economy the way it is. He's going to be an EE now, he gets all his school and living expenses paid for by unemployment insurance. Downside for him is he's "middle aged" now, so a lot of companies don't want to take him on as a new hire. I think his old company is likely to take him in as an EE though.
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Old 01-16-2011   #30
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Default Re: Capacitor Myth

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Originally Posted by FAUEE View Post
Capacitors have some great uses.

"Capacitors are NOT for letting you put in a "bigger system"
. Capacitors do not give you more energy. Capacitors will not give you more "watts".

A Capacitor is great for allowing a 4 channel amp to have instant access to all the Power it needs, and for cleaning up the Power generated by your alternator. Capacitors are also nice for helping to negate light dimming from using your windows, etc. while listening to your music. A big capacitor can be a good thing, and when used as a SUPPLEMENT, its a valuable piece of equipment.

If your amp pulls 200A and your Car only has a 110A alternator, a cap will not help you. In fact, it might make your problem worse. If your Car has an ailing alternator, and you have recently started to get light dimming from it, a capacitor will not help you and will help kill your alternator faster.

As an aside, I'm an EE here too. Wish i could get a nice internship at a power utility, I'd love to get a job in a power plant. Nice stable and high paying work there.

I couldn't imagine going through EE school to just be an electrician. The money's just not in the same league, and it's a whole lot of time spent for no reason. I can understand wanting to be more hands on (I'm the same way), but man, I just don't think I could make that same decision. EE is 5 years pretty much country wide now, that's a lot of time to get into something that's not what you graduated in.
Thank You FAUEE !

"Capacitor Myth Busted"
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Old 01-16-2011   #31
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Default Re: Capacitor Myth

Yes! Nice explination Oliver!

Working on an install plan for my 2013 Subaru Legacy. Will post a build log soon!
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Old 01-16-2011   #32
 
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Default Re: Capacitor Myth

How about a 3000 farad capacitor??
Maxwell 3000 Farad Ultracapacitor Supercapacitor, Solar - eBay (item 370416238952 end time Jan-30-11 17:19:37 PST)
6 of these in series
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Old 01-16-2011   #33
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Default Re: Capacitor Myth

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Originally Posted by sonikaccord View Post
I'm gonna replace my battery with these.

Actually, I'm poking fun now, but honestly 15 years ago people would have poked fun at people wanting to use LEDs for lighting. Nobody's laughing now, it's actually cutting edge and a very real future technology.
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Old 01-16-2011   #34
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Default Re: Capacitor Myth

Someone explain to me how a capacitor increases the load on a circuit. How does a capacitor use energy? I've always thought of them as an electrical accumulator, only a storage device.

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Old 01-16-2011   #35
 
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Default Re: Capacitor Myth

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Originally Posted by danssoslow View Post
Someone explain to me how a capacitor increases the load on a circuit. How does a capacitor use energy? I've always thought of them as an electrical accumulator, only a storage device.
It doesn't theoretically.

It doesn't pass DC current.
If you analyze it with AC current, it affects the impedence of the circuit but doesn't use energy, just stores it.
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Old 01-16-2011   #36
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Default Re: Capacitor Myth

If it doesn't use energy, then how does it raise the current demand?

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Old 01-16-2011   #37
 
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Default Re: Capacitor Myth

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Originally Posted by danssoslow View Post
If it doesn't use energy, then how does it raise the current demand?
It can't by itself.

When a capacitor is discharged, it basically just waits until the demand goes down and then it recharges itself when everything is equalized. It resists changes in voltage.
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Old 01-16-2011   #38
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Default Re: Capacitor Myth

Now see, that's what I figure. Others don't seem to believe that is so.

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Old 01-16-2011   #39
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Default Re: Capacitor Myth

You know, I've always thought this is weird. Why do they have 1 farad capacitors that are about the size of that thing or smaller, that thing which claims 3000 farads at that size, but most 1 farad capacitors in cars are the size for a thermos? Just because people think the bigger they are the better they must be?
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Old 01-16-2011   #40
 
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Default Re: Capacitor Myth

Quote:
Originally Posted by FAUEE View Post
I'm gonna replace my battery with these.

Actually, I'm poking fun now, but honestly 15 years ago people would have poked fun at people wanting to use LEDs for lighting. Nobody's laughing now, it's actually cutting edge and a very real future technology.
Yes, LEDs have a very bright future

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Old 01-16-2011   #41
 
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Default Re: Capacitor Myth

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Originally Posted by Sarthos View Post
You know, I've always thought this is weird. Why do they have 1 farad capacitors that are about the size of that thing or smaller, that thing which claims 3000 farads at that size, but most 1 farad capacitors in cars are the size for a thermos? Just because people think the bigger they are the better they must be?
It's a double layer capacitor. It's a new ish type of capacitor that packs in more capacitance per area. They call them, supercapacitors (real creative )

The big 1 farad caps are a bunch of hot air
YouTube - Inside a 2 Farad Car audio Capacitor--Gucci Mane--Hasta La Vista--

Yes, size sells.
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Old 01-17-2011   #42
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Default Re: Capacitor Myth

lol. I was actually thinking they would have a tiny 1 farad capacitor inside of it, like the little 1 farad capacitors one might see in a physics class, then just a bunch of padding. I wish I could tell what that stuff is, it looks like just some foam insulation mostly.
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Old 01-17-2011   #43
 
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Default Re: Capacitor Myth

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Originally Posted by Oliver View Post
Thank You FAUEE !

"Capacitor Myth Busted"
I have been debating this question. Thank you for helping in my decision.
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Old 01-17-2011   #44
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Default Re: Capacitor Myth

On a positive note about capacitors... In 1997, I had a 1996 Thunderbird with an impossible to solve noise issue. I tried everything I could think of and three different shops tried all sorts of things, but nothing worked. I called a buddy of mine who was out in California in the service and he told me to try a capacitor because it helped a noise issue in his truck. I installed a 1/2 farad capacitor and it filtered out the Power line generated noise that no one else could solve.

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Old 01-17-2011   #45
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Default Re: Capacitor Myth

Caps are indeed great for that. That's exactly why they are used in Power supplies: smoothing the Power signal.
A capacitor reacts a lot faster than a battery and especially older amps can't handle a seriously soiled power signal on their own, so adding a cap right in front of the amp(s) is the best way to clean the power signal up before it enters the amp.

The only reason why a cap also helps light-dimming issues is because it keeps the voltage as stable as possible, not only when the power coming from the battery/alternator is soiled, but also when an amp pulls the voltage down by asking more current than the load-system can handle.
The problem is a capacitor is actually too fast to do this. It will catch up the peak in the current demand, but it will recharge to 99.999% (a capacitor is never 100% full) as fast as it can, causing probably an even higher current-demand on the load-system and eventually drain itself and the battery, and kill the alternator when you play dynamic music at high volume level for a long time.
A bigger capacitor will only stretch this process.

An extra battery will also try to keep the voltage stable and catch up peaks in the current demand, but will recharge slower, causing less drain on the load-system.
Yes, this will eventually drain the load-system and maybe even kill it too if the extra battery has to catch up every single peak all the time, but that's why you have to start with a strong enough alternator and power wiring!


So:
- A capacitor is great for reducing distortion on the power signal, but NOT for dimming lights, whatever the size of it (smaller capacitors are even better in doing what they're designed for!!!), and now even the most critical people know and understand why!
- The only solution for dimming lights is upgrading power wires, alternator and battery-bank. It isn't called the BIG 3 for nothing!

/thread

Now can somebody make a permanent sticky of this that won't get lost when somebody messes with the forums again?

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Car-audio history since 2004:
- 2000 Renault Clio: cancelled... - 1992 Volvo 940: cancelled...
- 1990 Saab 900: cancelled....... - 1994 CitroŽn Jumper: cancelled...
- 1989 Volvo 740: cancelled...... - 1993 Saab 900: cancelled...
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Old 01-17-2011   #46
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Default Re: Capacitor Myth

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Originally Posted by Candisa View Post
but it will recharge as fast as it can, causing probably an even higher current-demand on the load-system and eventually drain itself and the battery, and kill the alternator when you play dynamic music at high volume level for a long time.
This is where I have doubts. I do believe a capacitor will only replenish itself as fast as the circuit will allow it to. Just like an accumulator, it can only take what is available. Since it uses no Power of its own (except for maybe a little dissipated in the form of heat), it will not consume any energy; therefore not putting any extra load on a circuit.

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Old 01-17-2011   #47
 
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Default Re: Capacitor Myth

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Originally Posted by danssoslow View Post
This is where I have doubts. I do believe a capacitor will only replenish itself as fast as the circuit will allow it to. Just like an accumulator, it can only take what is available. Since it uses no Power of its own (except for maybe a little dissipated in the form of heat), it will not consume any energy; therefore not putting any extra load on a circuit.
Incorrect, a capacitor is definitely a fairly lossy device, leave a charged Car capacitor sitting for even a minute and the voltage on it will have dropped significantly. This means that to stay at a constant voltage the capacitor will always have a parasitic draw. Also, after a voltage sag the capacitor will try and recharge itself once the voltage is above the voltage the cap dropped to. Everyone should read teh capacitor article on Wikipedia, it is helpful.

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Old 01-17-2011   #48
 
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Default Re: Capacitor Myth

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Originally Posted by bose301s View Post
Incorrect, a capacitor is definitely a fairly lossy device, leave a charged Car capacitor sitting for even a minute and the voltage on it will have dropped significantly. This means that to stay at a constant voltage the capacitor will always have a parasitic draw. Also, after a voltage sag the capacitor will try and recharge itself once the voltage is above the voltage the cap dropped to. Everyone should read teh capacitor article on Wikipedia, it is helpful.
ESR? There is leakage current that causes it to discharge on it's own but I see no reason why it shouldn't hold a charge for longer than a minute at it's charged voltage. Plus if the voltage is constant in a dc scenario, it acts as infinite resistance and the amp is pulling straight from the alt or battery voltage.

I agree, the capacitor will always try to match it's charging voltage.

Caps are passive(dumb), how can they cause an extra strain on the electrical system? They can't discharge below the lowest source voltage when it sags which is the same as drawing straight from the battery.
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Old 01-17-2011   #49
 
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Default Re: Capacitor Myth

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Originally Posted by sonikaccord View Post
ESR? There is leakage current that causes it to discharge on it's own but I see no reason why it shouldn't hold a charge for longer than a minute at it's charged voltage. Plus if the voltage is constant in a dc scenario, it acts as infinite resistance and the amp is pulling straight from the alt or battery voltage.

I agree, the capacitor will always try to match it's charging voltage.

Caps are passive(dumb), how can they cause an extra strain on the electrical system? They can't discharge below the lowest source voltage when it sags which is the same as drawing straight from the battery.
This is true, but they also need to charge back up after the drop pulling more from the system. I actually had a crappy Scosche .5 farad cap from Wal Mart that I was messing with in a lab at school, it was not from my Car or anything, it was from a project we did, but I would charge it up to ~18V just for fun then let it sit, it discharged suprisingly fast just sitting there. Maybe higher quality capacitor are better for this but thats all I had.

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Old 01-17-2011   #50
 
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Default Re: Capacitor Myth

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Originally Posted by bose301s View Post
This is true, but they also need to charge back up after the drop pulling more from the system. I actually had a crappy Scosche .5 farad cap from Wal Mart that I was messing with in a lab at school, it was not from my Car or anything, it was from a project we did, but I would charge it up to ~18V just for fun then let it sit, it discharged suprisingly fast just sitting there. Maybe higher quality capacitor are better for this but thats all I had.
Sounds like an interesting experiment.
How many cases does a capacitor work in? I've seen all this talk about caps don't work but none about a capacitor fixed this.
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