caps - what do they do or what do they supposedly do?

[jlaine 10+ year member]

geolman, what about my question for spl purposes. Same system with and without caps, will i notice an spl difference on the first burp?

Ask some serious SPL people that question.

And take a good look at how many have caps in their vehicles. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[geolemon 10+ year member]

No, but you are driving the car, are you not?
Or do we all sit at idle for 4 hours at a time pegging our system?

No, but these are actually both points that are perfect...

We are driving, but only during accelleration or freeway speeds do we end up anywhere over 2000 rpm, most often right in that 1000-2000 range. That's still quite low.

And how often are we actually pegging our system?

That's the other consideration.

Installing the alternator is a "the penalty is always there" solution that provides a "the benefit is only sometimes taken advantage of" application. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

And it still doesn't stop your headlights from dimming, if you truly do have a large-draw situation.

If you notice the "HP robbing alternator" - you have about 3 squirrels for a engine. I suggest you shoot the car now.

I haven't the luxury of driving a car immediately preceeding and following an HO alternator installation to compare performance and effiicency.

However, let's compare something that is similar with this respect, as it's a drag on the engine -

Consider turning on your A/C. While the A/C pulley is always spinning, when engaged the compressor puts additional drag on your motor, and you can feel that - and it does make a noticable dent in accelleration and passing power.

I've noticed that with cars small to large...

• I have a 1.6l Honda Civic that's got some performance goodies. Noticed it both before and after installing a supercharger on the car, 125hp before, 195hp after, noticable both before and after.
  
• My wife has a 2.0l VW new beetle, very noticable on her car, particularly being an automatic.
  
• I have a Nissan Pathfinder, 3.0l V6. Noticable again, even being a 5 speed (automatic is against my religion).
  
• My best friend has a Z28 Camaro, 5.7l V8, show car, modified with performance goodies. Noticable on that car also, again his being an automatic, you can tell particularly in throttle response and shift point differences.
  

This is just a pure statement regarding the drag on a motor.

The additional drag on the motor related to the alternator should be relatively easy to predict, simply due to the law of conservation... it should be proportional to the difference in current, between your new alternator and old one (assuming similar efficiencies, of course. Not too many variables in alternator technology relating to that really).

That's personal opinon - not factual documentation. It's pretty much impossible to turn around and go "my subwoofer is inefficient, there... fixed." The listening habits of people vary quite drastically. Your idea of adequate, is NOT someone elses.

If you have a 12" subwoofer stuffed into a 1/2 cu.ft. box... sure, that sub might soak up 1200 watts without coming close to it's excursion (or output) capabilities.

But if you put that same sub in a larger enclosure, possibly ported... you might get not only the desired increases in output, but you might reach that with only 400 watts even.

That's the point.

If you have a system that's soaking up the power of a Viper 2500D, sending your electrical system to it's knees, but you aren't satisfied with the results, there are probably gains to be had by revisiting the enclosure design.

Installing an alternator would be a band-aid, masking the true problem, which would be an inefficient enclosure design.

The enclosure drives efficiency orders of magnitude greater than the internal efficiency of the subwoofer itself.

And Hoffman's Iron Law defines what you can trade off to gain efficiency, in designing that enclosure.

...popped 100 bucks out to install something that is a half-assed attempt at a repair. Not a primary supply device, it's just a storage unit.

Exactly!

It's not a primary supply device.

It's installed to augment, to help your electrical system respond to this nasty thing hanging off your electrical system (ahem.. the amplifier) that's trying to demand current faster than your electrical system can deliver it.

 

[jer_stud56 10+ year member]

Ok whenever I come on here, someone is asking a cap question (no offense, but please, just use search next time) and then others get into an arguement on whether caps are good for everyone. And the fact is no. Not all cars are the same, nor are all drivers, nor are all systems, nor are the alternators and the electronics in them, whether stock or not. If you find out that a cap helps out you're electrical system some, then go for it, use it, experiment with it. If you don't like it then take it back. Quit the fightin and enjoy the season.

- pe@ce

 

[jlaine 10+ year member]

Power is cheap.

People don't like taking up a lot of trunk space. Take a really good look at manufacturer recommended enclosures for a second, so you can properly grasp what's popular. I'd rather dump 1kW into my subwoofer than have to give up 2 cubes of space if I needed my trunk for something other than car audio crap.

Transient dimming? When I went from my *stock* 100A alternator to my *aftermarket* 180A unit - my light dimming went away... And my transient potential far exceeded 180A at that time. No caps in the car then either.

Alternator drag... My LS1 sure doesn't seem to mind that dinky little alternator attached to it.

 

[n2audio 5,000+ posts]

I'm really not very concerned about this topic. I simply know that if I'm going to add a $100+ component to my system it's sure as hell not going to be something that may or may not help, and in the case that it does help I'm probably not going to hear any difference anyway.

But I do want to say -

Geo - what exactly would you expect RC to do - test a cap by the second? Do you often get in your car and blast it for 30 seconds at at time?? I haven't seen the graph, but there's a little thing called the law of conservation of energy - of COURSE the curve is the same.

The man is an accomplished scientist in his field. Easily one of the most recognizable and respected by his peers. If you're going to nitpick at him it would probably be a good idea to choose something other than his scientific method.

 

[paikiah 5,000+ posts]

you guys lost me again...

 

[maylar 10+ year member]

You linked me to an electronic gizmo that's not a battery, seems to simulate NiCD batteries, and doesn't have any references to the response speed of a battery in comparison to a capacitor. I'm confused by that.

I can't comment on deep cycle vs regular batteries, as I have no direct knowledge in that area. What I will comment on is the generic statements circulating around (including yours) that caps help car audio because they're faster than batteries.

That gizmo simulates drycell batteries with as much accuracy as the state of the art in electronics allows. The relevance is that batteries are so fast that it takes sophisticated equipment like this to simulate them. The limits of the machine are 20usec, and if that's typical of battery performance then we certanly don't need caps on our systems to make it any better.

But... according to the link you provided, it should take "minutes" for my flashlight to turn on.. or did I read that wrong? //content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif

Believe it or not, I used to be a proponent of caps in car audio. I could easily create an experiment that'd show how the system voltage could be more stable with a cap, just by introducing some series resistance in the wires.

That's what it's all about. Resistance losses. Not chemical-action vs static charge.

 

[helotaxi 5,000+ posts]

Do you run a whole bunch of dry cells in your car? NiCd and NiMH and alkaline batteries have much different charge/discharge properties than the lead acid/SLAB/Gel Cell used in a car.

 

[z24max 10+ year member]

all an otipma batter is a dry cell and it can be drained and rechared more times than a wet cell bat. on the other hand if you want a cap. put one in and make your own decision on how it works. i havent had to replace my stock altenator with my cap so i think it works since my friend has gone through three altenators with out one.

 

[jer_stud56 10+ year member]

Well I have some spare batteries and some spare caps around (from other electronics), and I'm going to try to hook my car amp up to them, we'll see what happens, although this doesnt include any other electrical equipment and alternators or anything, we'll see, maybe. lol.

- pe@ce

 

[helotaxi 5,000+ posts]

all an otipma batter is a dry cell and it can be drained and rechared more times than a wet cell bat. on the other hand if you want a cap. put one in and make your own decision on how it works. i havent had to replace my stock altenator with my cap so i think it works since my friend has gone through three altenators with out one.

Actually its a SLAB (sealed lead acid battery). The two are not the same.

 

[z24max 10+ year member]

thanks for the correction helotaxi

 

[cdr 10+ year member]

wooh you really must be reading this wrong maylar

But... according to the link you provided, it should take "minutes" for my flashlight to turn on.. or did I read that wrong?

never anywhere did anything such as this come up minutes to turn on a flashlight? your exaggeration is simply dimishing your argument...

 

[maylar 10+ year member]

wooh you really must be reading this wrong maylarnever anywhere did anything such as this come up minutes to turn on a flashlight? your exaggeration is simply dimishing your argument...

OK, a flash camera not a flashlight. Here's what it says:

"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 itself. That's why the electronic flash on a camera uses a capacitor."

That's simply not true. Electronic flashes have small dc-dc converters that boost the voltage (that's the whine noise you hear). The converter has too high an impedance to trigger the flashtube, so they charge up a cap. That's what I've been saying here.. it's all about source impedance, not speed.

In the old days of flashbulbs, no caps were required. And it didn't take "minutes" to take a picture.

 

[idontwant1 10+ year member]

ive had a soundstream 10.0 that dimmed my lights i added a cap and the dimming went away ..thats real world application no theory behind it ...theres another guy in this argument ..i mean post who had the same luck ..tha fact is caps seem to work for a lot of people and for alot of applications ...ive been looking and the biggest aqlt i can find for my application withount fabbig up brackets is a 90 amp ...so ill be running a yellowtop out back with caps ...