Combining capacitors of different sizes?

[Eric Pulliam]

Is there a problem with using the bars to connect multiple caps that
arent all the same size? They range from 1F to 1.5F. I was wondering
if since they are different in size they probably have different
charge and discharge rates, would one be discharging into another
possibly causing an overcharge or damage? There are 4 caps total and
the bars connect them all together. Any help would be appreciated.

Thanks!
Eric epulliam at ameritech dot net

[arthur[_5_]]

Connecting same trype capacitors in parallel reslults in adding
their values together. Connecting them in series causes the
total value to decrease ( the math is more complex ).

All you people keep thinking of capacitors in terms of DC which is a
static view and invalid in a dymanic circuit.

It should work fine. You are lowering the operating frequency in
a low pass filter.

arthur


On Wed, 26 Sep 2007 15:32:05 -0700, Eric Pulliam
> wrote:

>Is there a problem with using the bars to connect multiple caps that
>arent all the same size? They range from 1F to 1.5F. I was wondering
>if since they are different in size they probably have different
>charge and discharge rates, would one be discharging into another
>possibly causing an overcharge or damage? There are 4 caps total and
>the bars connect them all together. Any help would be appreciated.
>
>Thanks!
>Eric epulliam at ameritech dot net

[Matt Ion]

arthur wrote:
> Connecting same trype capacitors in parallel reslults in adding
> their values together. Connecting them in series causes the
> total value to decrease ( the math is more complex ).

Not all that complex... 1/C1 + 1/C2 + 1/Cx... = 1/Ctotal: just invert
the values, add them together, and flip them back. If you have a 1F and
two 2F caps in series, you'd get 1/1 + 1/2 + 1/2 = 2/2 + 1/2 + 1/2 = 4/2
.... invert to 2/4, and you end up with 1/2F total.

The only time you'd really want to do this is if the caps you have are
rated too low a voltage for your circuit, as the voltage ratings are
additive for series-connected caps (ie. two 6VDC caps in series will
give you a total breakdown of 12VDC). Not likely to be an issue with
car-stereo caps.

> All you people keep thinking of capacitors in terms of DC which is a
> static view and invalid in a dymanic circuit.

I dunno about your car, but mine operates on DC voltage...

> It should work fine. You are lowering the operating frequency in
> a low pass filter.

Essentially, yes.

The REAL question, is whether you actually need ANY caps at all, let
alone a ****load of them. The answer in MOST cases is, "not really."


> On Wed, 26 Sep 2007 15:32:05 -0700, Eric Pulliam
> > wrote:
>
>> Is there a problem with using the bars to connect multiple caps that
>> arent all the same size? They range from 1F to 1.5F. I was wondering
>> if since they are different in size they probably have different
>> charge and discharge rates, would one be discharging into another
>> possibly causing an overcharge or damage? There are 4 caps total and
>> the bars connect them all together. Any help would be appreciated.
>>
>> Thanks!
>> Eric epulliam at ameritech dot net

[arthur[_5_]]

Alternators output A/C
igition systems are A/C
Sound waves are A/C

what's your issues?

arthur



On Thu, 27 Sep 2007 07:31:56 GMT, Matt Ion >
wrote:
>
>I dunno about your car, but mine operates on DC voltage...
>

[buddha73[_2_]]

Kirby Wrote:
> I would stay away from the capacitors completely. Get a second battery.
> A
> cheap one, or good one will do the same, if not more help to your
> system.
> Not to mention it doesnt need to be charged as fast as a cap, so it
> takes a
> BIT of strain off of your alternator.

wrong, capacitors charge very quickly, batteries would supply you with
more amperage, but only 12.5v. now getting a nice high output
alternator would be better than a cap or a battery. adding a second
battery would put way more strain on your alternator so you'd probably
have to upgrade that too if you get another battery.


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[Matt Ion]

arthur wrote:
> Alternators output A/C

Alternators output AC... the ONLY place the AC goes is into a regulator
that outputs DC. Everything else in the car's system runs on DC.

> igition systems are A/C

Wrong. The closest thing in it to AC is the spark system itself, which
is pulsed DC.

> Sound waves are A/C

Irrelevant.

> what's your issues?

Your supposition is incorrect. The kind of caps we're talking about
here are used in the DC circuit powering the amp.

> arthur
>
>
>
> On Thu, 27 Sep 2007 07:31:56 GMT, Matt Ion >
> wrote:
>> I dunno about your car, but mine operates on DC voltage...
>>

[Kirby]

I would stay away from the capacitors completely. Get a second battery. A
cheap one, or good one will do the same, if not more help to your system.
Not to mention it doesnt need to be charged as fast as a cap, so it takes a
BIT of strain off of your alternator.

[g]

In article om>, Eric Pulliam > wrote:
>Is there a problem with using the bars to connect multiple caps that
>arent all the same size? They range from 1F to 1.5F. I was wondering
>if since they are different in size they probably have different
>charge and discharge rates, would one be discharging into another
>possibly causing an overcharge or damage? There are 4 caps total and
>the bars connect them all together. Any help would be appreciated.

If you hang caps of different sizes off a bar, its probably going to look
pretty weird, or perhaps the bottoms are in a well where you can't see them.

You will have no problems regardless.
Cap value is not controlling discharge rates. ESR is. The cap needs to be
measured for ESR. The manufacturer should give that figure.
Cap values means nothing if ESR is high. A very high ESR wold be OK to use
feeding a headunits keep alive voltage. I actually did that once on my boat.

greg

[arthur[_5_]]

Forget it. I obviously did not understand the question.
As an aside, an auto battery already acts as a huge capacitor and as
such does not work well filtering high frequencies.

arthur



On Thu, 27 Sep 2007 01:23:45 -0700, arthur > wrote:
>Alternators output A/C
>igition systems are A/C
>Sound waves are A/C
>
>what's your issues?
>
>arthur
>
>On Thu, 27 Sep 2007 07:31:56 GMT, Matt Ion >
>wrote:
>>
>>I dunno about your car, but mine operates on DC voltage...
>>

[Christopher \Torroid\ Ott]

"Eric Pulliam" > wrote in message
ups.com...
> Is there a problem with using the bars to connect multiple caps that
> arent all the same size? They range from 1F to 1.5F. I was wondering
> if since they are different in size they probably have different
> charge and discharge rates, would one be discharging into another
> possibly causing an overcharge or damage? There are 4 caps total and
> the bars connect them all together. Any help would be appreciated.


The short answer is that it'll be fine. Yes, they would have different
individual time constants if they weren't tied together with a buss bar.
Since they are, we can view the group as one large capacitor. The values
will add together. For automotive use the individual ESR's can be ignored.

From an electrical standpoint the caps should be placed close to your amps,
since they are what pulls the instantaneous loads. Alternatively, I've seen
several mounted under the hood, and know for a fact that it's also
effective. The very best SQ car I've ever seen was Scott Buwaldas 240SX. It
had (3) 1F caps under the hood, approx 10 feet from the amp rack. He felt it
made a significant improvement. This was a world class SQ vehicle, and
Buwalda was neurotic about the quality of his system.

Chris

[Matt Ion]

G wrote:
> In article om>, Eric Pulliam > wrote:
>> Is there a problem with using the bars to connect multiple caps that
>> arent all the same size? They range from 1F to 1.5F. I was wondering
>> if since they are different in size they probably have different
>> charge and discharge rates, would one be discharging into another
>> possibly causing an overcharge or damage? There are 4 caps total and
>> the bars connect them all together. Any help would be appreciated.
>
> If you hang caps of different sizes off a bar, its probably going to look
> pretty weird, or perhaps the bottoms are in a well where you can't see them.
>
> You will have no problems regardless.
> Cap value is not controlling discharge rates. ESR is. The cap needs to be
> measured for ESR. The manufacturer should give that figure.
> Cap values means nothing if ESR is high. A very high ESR wold be OK to use
> feeding a headunits keep alive voltage. I actually did that once on my boat.

Cap value is DIRECTLY controlling the discharge rate. T=RC, one of the
most basic formulas in electronics: time = resistance times capacitance.

[Matt Ion]

Eric Pulliam wrote:
> Is there a problem with using the bars to connect multiple caps that
> arent all the same size? They range from 1F to 1.5F. I was wondering
> if since they are different in size they probably have different
> charge and discharge rates, would one be discharging into another
> possibly causing an overcharge or damage? There are 4 caps total and
> the bars connect them all together. Any help would be appreciated.
>
> Thanks!
> Eric epulliam at ameritech dot net

Alright, there's a whole bunch of goofiness and misinformation going on
in this thread, so let's clarify a few things (all of which have been in
the FAQ for over a decade):

1. The single cheapest, simplest upgrade you can make to your car's
electrical system is the wiring; specifically, the wires connecting the
battery to the chassis, the engine block to the chassis, and the engine
block to the battery. It doesn't matter how big your power wire is from
your battery to your amps if your ground path is squeezed down into a
little dinky 14ga. jumper.

2. EFFECTIVE electrical system upgrades (after the wiring upgrades) are
done in the following order:

- 1. high-output alternator. Caps and batteries can only store energy.
That energy has to come from somewhere in the first place, and
that place is your alternator. If your system is sucking more
juice than your alternator can provide, then any other "fixes"
will at best buy you a little time.

- 2. high-capacity battery. Preferably a separate, dedicated battery
for your system, using a battery isolator (the kind you find in
RV stores). Remember that cars have batteries in the first place
for one reason: to crank the starter. Running accessories with
the engine off, and backing up clocks and station memories, are
secondary. Once your engine is running, your alternator should
be providing all the power needed for your car's systems,
including your stereo system, and to recharge the battery from
whatever drain it sustained with the engine off. A separate
battery for the stereo system will ensure that you're never
stuck anywhere because of cranking your system for too long
with the engine off.

- 3. capacitors. Actually, this one comes a very distant three.
Throwing a ****load of capacitance at your system will really
make little or no difference unless you're REALLY pulling a
lot of amperage, and even then, it's REALLY only useful for
very brief moments. Given the resistance of the wire feeding
it charging power FROM THE ALTERNATOR (NOT the battery), a
cap will typically recharge far slower than it discharged,
and if you're running sustained long, low, droning notes, it
will never have a chance to recharge, and thus not provide any
benefit.

90% of guys who throw a bunch of caps at their system because some joker
told them it would "help them hit harder" are wasting their money,
especially since they've done none of the other upgrades that will
really facilitate the caps being of any benefit.

[MOSFET]

> All you people keep thinking of capacitors in terms of DC which is a
> static view and invalid in a dymanic circuit.
>
LOL.
He said "static" in relation to capacitors (said in the voice of Butthead).

MOSFET

[Matt Ion]

MOSFET wrote:
>> All you people keep thinking of capacitors in terms of DC which is a
>> static view and invalid in a dymanic circuit.
>>
> LOL.
> He said "static" in relation to capacitors (said in the voice of Butthead).

Huh huh huh. Uh... that was cool.

[Kirby]

well my alternator is holding up very well for being a stock 55 amp. I have
3 batteries, and drawing a max of 500 amps. I say that number VERY
generously.

[Kirby]

it's lasted a while already.