anyone use a capacitor?

[ma deuce]

how well do capacitors work? are they just for show or do they help? thanks

[drdx]

I've never used one but would like to try a huge one. Most anyone in the cb hobby will tell you they don't work but a few report good results by using one to cushion the blow of having a high amperage drawing setup. I personally think that a big enough one may put a band aid on a marginal charging setup but in the end it is your alternator that has to do all of the charging, the charging of that capacitor included. I'll never know until I bite the bullet and try one. I'm just waiting on a deal so I don't get burned if it doesn't work.

-drdx

[Red Warrior]

One farad capacitors are used extensively by car audio enthusiasts to deliver surges of power during bass transitions such as drum beats. They are relatively useless for transmitter use and generate HF RF during recharge generating noise in your receiver.

[Hazelnut 7201]

I have also read "one farad per 1000 watts" and I, like drdx, am considering one.

They are relatively useless for transmitter use and generate HF RF during recharge generating noise in your receiver.

Red Warrior please elaborate:

If they generate HF RF during recharge, are there different capacitors available that don't? Why does Radio Active have them on his web site? Does he also do car stereo's?

"They are relatively useless for transmitters use" Please explain. I don't understand the logic here, a water pump, heater element or welder will draw a constant load and any short term boost in current would do little good. Ok, maybe if you whistled a steady tone or used a signal generator into the mic you would create a steady load on the alternator/battery and again the capacitor would be of little use. But I am not a bird and I can't hold my breath that long.
Have you ever watched the VU meter on your radio dance as you talk into the mic? What about those watt meters with the RMS and PEP functions? The RMS is your average power and the PEP is peak watts. Humm, let's see, the rule-of-thumb on RMS and PEP watts is something like RMS watts are 50% of the PEP watts. How are peak watts different than the bass thumping on a stereo?

I have no plans on installing a "slow blow" fuse to protect my radio. I have seen negative posts on capacitors before and I have yet to see where someone has explained why.

Thank you.

[Texas Mobil 219]

I always thought that Capacitors were used in Key down events. I dont know much about them. But what i do understand is that the will take alot of drain off you system. Its just something to back up the sudden drain and slap your singal out and over others.

[Foxhunter]

I'm going to paste this very same answer from another thread I answered recently rather than re-type. Do I use them? Yes. Do I have any ill or unwanted side-effects from them? No. Would I recommend their use? Yes and no. Yes if you have them spare just lying around, no if you have to go spend $100+ on each of them (yes I have over $300 in capacitors). I've used up to three 1-farad or larger capacitors wired in parallel.

Chiefly I see an excellent form of noise-reduction and a fill-in of the lag-time from load demand to alternator response. They are NOT an alternator, a battery or a motor maul.


From experience & common sense it's easily understood that although the alternator is a source of renewable power-----more importantly it is the source of voltage fluctuation, electrical noise/trash and other maladies. The battery(s) are most often needed as a buffer/filter, with beneficial stored current reserve. Running an amp straight from the alternator would introduce all sorts of problems and negative side effects.



Sometimes people mention using an amplifier from just a battery with the engine off. Running an amplifier system without a running charging engine is almost an excercise in futility. "Resting Voltage" (voltage of a battery not being charged/replenished by an alternator) for most automotive batteries is only 11.5VDC. A nominal voltage of a battery considered "dead" to electionics and other DC applications is 10.5VDC. Even with a fresh battery, that's only one volt away from being considered completely dead. Far too low voltage.


In the battery-only scenario, an amp/radio combination would be powered at 11.5VDC at the battery, then factor-in a voltage-drop along the length of the supply cables PLUS an insertion loss of any cable connections crimps connectors etc-----you would be running your amp/cb in "brown out" conditions and it would deplete the battery in short order.


Anyway, back to capacitors . . .

Electrolytic filter capacitors, also known as car audio stiffening capacitors? Although their use is often misunderstood and at times hotly debated, I am still from the side of opinion that they can be a benefit.


Not only from a concept point-of-view, but from actually having used them. They just cannot be relied on to actually "power" a system, either car audio or rf amplifier based systems. That is where many go wrong, thinking they can put one in-line----and suddenly----with an otherwise stock charging system they expect to power a 1000W amp. Critics also cite this misunderstanding and misuse in application and wrongly deem them entirely useless.


They are not a replacement for a good or extra battery nor a replacement for an adequate high-output alternator. What they are however is a good accessory for bolstering a "marginal" charging/battery system whose maximum rating is at that point already close to actual demand. They can be useful for highlighting or functionally complimenting (if you will) an already adequate charging/battery system. The electronic noise reduction, voltage fluctuation stabilization, momentary surge capacity and other benefits can be a boon to your otherwise decent supply system. At the initial point when a heavy demand/load is placed on the system, there is a small lag time where a power supply system responds with increased output. The alternator doesn't respond in an instant. But a capacitor will. It is only in that momentary initial lag where a capacitor can be found useful. They are not to be used as a band-aid measure or crutch to a really inadequate system.


I believe another misconception is that they somehow "rob" your alternator of power. A capacitor only takes power from the charging system during lulls where demand is at a low and energy is at a surplus. In situations of peak demand they simply continue to allow current to pass through, waiting to recharge when demand is minimized. For me it's hard to justify the cost of capacitors as an accessory, but if they are readily available I wouldn't hesitate to use them. A stiffening capacitor is not a "critically necessary" item, but then again much of what is contained and utilized in the radio hobbies really isn't absolutely necessary. IMHO it would be for the premium-install crowd, where in addition to a proper charging/supply installation, expensive accessories such as these are considered reasonable and affordable.


There was a large thread that has about 2000 views so far and many replies on this very same subject:
The Use of High-Farad Capacitors With Amps
[Please login or register to view this link]

[Red Warrior]

I have also read "one farad per 1000 watts" and I, like drdx, am considering one.

They are relatively useless for transmitter use and generate HF RF during recharge generating noise in your receiver.

Red Warrior please elaborate:

If they generate HF RF during recharge, are there different capacitors available that don't? Why does Radio Active have them on his web site? Does he also do car stereo's?

"They are relatively useless for transmitters use" Please explain. I don't understand the logic here, a water pump, heater element or welder will draw a constant load and any short term boost in current would do little good. Ok, maybe if you whistled a steady tone or used a signal generator into the mic you would create a steady load on the alternator/battery and again the capacitor would be of little use. But I am not a bird and I can't hold my breath that long.
Have you ever watched the VU meter on your radio dance as you talk into the mic? What about those watt meters with the RMS and PEP functions? The RMS is your average power and the PEP is peak watts. Humm, let's see, the rule-of-thumb on RMS and PEP watts is something like RMS watts are 50% of the PEP watts. How are peak watts different than the bass thumping on a stereo?

I have no plans on installing a "slow blow" fuse to protect my radio. I have seen negative posts on capacitors before and I have yet to see where someone has explained why.

Thank you.

Audio capacitors store power an audio amplifier needs to fill current demands on the electrical system during big bass notes. They store power during intervals when it is not required, and release it when peak demand exceeds what is available from the car's power system. A capacitor will supply current for less than 1 second duration.

After you have discharged the capacitor, the capacitor will need to recharge. How does it recharge? Well, the capacitor sits in between your battery and your amplifier. Once the capacitor is discharged, it will attempt to charge itself by drawing power from your battery reducing the amount of power your amplifier can draw. When the amplifier needs power, the capacitor will supply current from the battery as well as any "extra" current it has saved up. Once its discharged, the cycle continues. In a radio circuit, this will appear as variations in transmit power as the available current varies with the charge cycle of the capacitor. If the transmitter is not seeing variations it is because the capacitor is not charging/discharging and therefore was not needed in the first place.

Most common car audio capacitors are rated at 1 farad, while 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. When your amplifier needs current, it will suck the capacitor dry in less than one second, leaving your capacitor to use your battery to charge up again. Once the capacitor is charged, that extra current can then be transferred onto the amp.

If a capacitor can only hold a charge for less than one second, while drawing substantial amounts of current from your battery in an attempt to charge back up while delaying power to the amplifier, then what is the point? There is none. Capacitors are known in the car audio community 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, while not straining your electrical system.

As far as the capacitor generating noise, this is from personal experience from numerous CB'rs and Hams who have reported this noise from loud audio systems in local cars. We traced the spikes in noise to the charge/discharge of the car audio capacitors in the vehicles. Most installations use a filter capacitor to remove the noise but self-installers often omit this step.

Paint your antenna pink, you'll get better results.

[drdx]

Thanks to all that have contributed here, as I'm here to learn. Wouldn't the length of time the capacitor could supply power before discharging depend on the size of the capacitor and the demand? I see one of those big capacitors as a big elastic battery, short term, quickly charging and discharging, cushioning peaks in draw. Am I way off here? I'm seeing things in a general fashion, and like the audio scenario, I don't see much difference in audio peaks on a song and audio peaks on radio transmissions, other than the fact that on a radio transimission the duty cycle is much less, giving the system more time to recover.

Are capacitors that shallow and worthless? I'd think a multi farad capacitor on a kw setup would offer some cushion, but I've never used one.

-drdx

[Foxhunter]

Well I'll leave the pink antenna painting to others.


I've far better results than some and received many many unsolicited compliments on my stations both mobile and base, maybe I'm just lucky. In the mobile I've used them wired in parallel. In the home station I still use them in conjunction with several big DC power supplies, using 3 caps in parallel. No negative effects whatsover-------in drop/draw/noise/damage etc etc etc. In recent years I've had good Simpson volt and ammeters in-line to monitor everthing I've tried. I'd have quickly tossed the caps if I saw a negative indication.


Audio stiffening power capacitors accumulate power whenever it is not required. This power is only released when the demand for power exceeds the supply capacity of the power system of the car, whatever it might be. The capacitor will not compete with the load for current, it will recharge in surplus conditions.


The response time (or lack of) of an alternator must be fully taken into account. There is a brief lag. The caps will quickly insert or quickly "inject" a huge amount of current right into the load at a short critical time when it is needed most, at initial draw. That's all, that's all there is to it. From there the alternator and batteries sustain the load, the amplifier.

[Red Warrior]

Let’s look at this from an engineering perspective. What problem are we trying to solve? We have a radio transmitter in a mobile that requires a certain amount of current to operate correctly. If we use the formula Amps = Watts/Volts and say our maximum swing is 1000 watts and our voltage is 14 volts. The current we need to support our transmitter (not considering other car systems) is 1000/14 = 71.4 amperes. That is the maximum surge we need. If we have an alternator capable of 150 amperes, we have twice what we will ever need and capacitors are not required or even useful.

For discussion sake let’s assume the battery/alternator will only supply 70 amps. In this case we have two solutions. 1) Add a bigger alternator/battery to increase capacity. 2) Add a load leveling capacitor in the circuit to fill in the surges to 71.4 amps. A 1-farad capacitor can hold 1 amp-second of electrons at 1 volt. Therefore a typical 1 farad capacitor will hold 14 amp seconds of electrons at 14 volts. In theory we can get 10 seconds of 1.4 amp surge from one capacitor followed by about 10 seconds of current limit as the discharged capacitor becomes another load on our power supply.

Do you need additional capacity? Do the math. Which solution is best? Here is where the argument starts.

[drdx]

Wow, if that's their capacity, then I understand the reason they wouldn't work, as you would need a truckload of them to help. I run a battery right next to my amps in the back, 2 inches from one amp, 6 from the other, with a very short fused blocked thick power cable feeding them, so it probably wouldn't apply to me, but I always thought that for someone running an amp way in the back, with marginal charging and wiring, it may offer a little help being right at the amp. I visualized, as I think foxhunter was eluding to, the cap filling in the gaps between the power peaks. I figured it would help maintain voltage and for a big swinger, and that's not me, I'm a mauler, it may stretch the needle up a bit on a peak meter. Well, at least I didn't spend any money. Good news though, optimas are cheaper at my Sams store than they have been in a while.

As a side note, I'd always heard on here that they wouldn't work for our application but then in CQ magazine I see that mfj is offering a small power supply with a stiffening capacitor in it. I think it is being marketed as a power supply but I could be wrong. But then again, they're kinda the JC Whitney of the radio world.

-drdx

['Doc]

And what all of this has told me so far is that there is a lack of source power. In such a condition a capacitor may supply a very limited amount of that power lack for a short time. The down side of that is that capacitor also is supplying another draw on the system. That's the price you pay for it supplying that short surge of power.
The limiting factor is that inadequate source of power. It will be under an increased load, there is no way around that. Increasing the power storage capacity can affect the total supply, but the source will still have to replace that used power.
So instead of 'bandaiding' the problem, why not just 'cure' it at the 'source'?

As for capacitors causing noise, I've never had that experience. At least not in the primary power circuits. Other places, I guess they could contribute to noise, maybe, if chosen incorrectly. That typically indicates a goof in design or construction. In primary power circuits, any noise is usually a result of too small of a capacitor(s) used for filtering, not a too large capacitor.
- 'Doc

[Hazelnut 7201]

I understand that a capacitor is only intended to supply the initial surge, not the total current load, and that they will recharge as fast as they discharge.
So if you max out your capacity 5 times during a 10 second transmittion and each peak is less than a half a second, there should be plenty of time for the capacitor to recharge without competing.

A battery/charging system works on a supply and demand principle. It can not predict what the demand will be, only supply it after a demand is made.

My question is: Will a capacitor at 20 volts respond faster than a battery/alternator system at 13.8 volts, reguardless of amp rating on the alternator?
The rational that voltage is the pressure component of electricity and amps are the size of the flow. Volts X Amps = Watts
A 1/2 inch (amps) water line @ 100 psi (volts) will respond more violent when it is cut than a 2 inch (amps) water line @ 10 psi (volts). Both water lines will get you wet, but the 1/2 inch @ 100 psi will get you wet from head to toe almost instantly. The 2 inch water line will just soak your sleeve and shoes. I think that the purpose of the capacitor is to get you wet from head to toe almost instantly until the 2 inch water line can give you a good soaking.

['Doc]

Is there any difference between using a capacitor in this way in an automotive electrical system to prevent 'sag', than a power supply's output at home?
- 'Doc

[Red Warrior]

I understand that a capacitor is only intended to supply the initial surge, not the total current load, and that they will recharge as fast as they discharge.
So if you max out your capacity 5 times during a 10 second transmittion and each peak is less than a half a second, there should be plenty of time for the capacitor to recharge without competing.

A battery/charging system works on a supply and demand principle. It can not predict what the demand will be, only supply it after a demand is made.

My question is: Will a capacitor at 20 volts respond faster than a battery/alternator system at 13.8 volts, reguardless of amp rating on the alternator?
The rational that voltage is the pressure component of electricity and amps are the size of the flow. Volts X Amps = Watts
A 1/2 inch (amps) water line @ 100 psi (volts) will respond more violent when it is cut than a 2 inch (amps) water line @ 10 psi (volts). Both water lines will get you wet, but the 1/2 inch @ 100 psi will get you wet from head to toe almost instantly. The 2 inch water line will just soak your sleeve and shoes. I think that the purpose of the capacitor is to get you wet from head to toe almost instantly until the 2 inch water line can give you a good soaking.

A capacitor will only charge to the voltage connected to it regardless of rating. A Capacitor with a 24 volt rating if connected to a 12 volt source will only charge to 12 volts.

A capacitor is only necessary if the vehicle charging/battery is not up to the task of supplying the necessary current. Even then the benefit is marginal at best. By far the best solution is to size your alternator/battery to meet your amplifier needs plus 10%.

A capacitor is no faster at responding to load demand than a battery. There is a school of thought that by placing the capacitor nearer the load (amplifier) than the battery it will provide better load response. Only true if the load is several hundred feet away from the battery. Otherwise you are talking microseconds in response difference.

[Foxhunter]

All good replies and I can't agree more with most if not nearly all of what is written. Red Warrior, Doc and DrDx are some of the best contributing CBRT Forum members and I greatly value their posts they care to write to many of us.

A battery/charging system works on a supply and demand principle. It can not predict what the demand will be, only supply it after a demand is made.

That's absolutely true and what is what I've been trying to say. Being around cars and peformance speed parts my whole life it's helped me understand the automotive end of the contoversy. There is a response lag time involved, and as Red Warrior said the capacitor should be placed right beside the load.

Restated, a capacitor is NOT a replacement for a high output alternator, a heavy-duty charging system (heavy cables, high output coil, high heat plugs, MSD ignition) and more-than-sufficient CCA rated battery or batteries. A capacitor is NOT intended to replace any of the above, only compliment them. Use for anything other than that is nothing but a band-aid.

As DrDx mentioned, yes many power supplies utilize them and they make excellent voltage stabilizers and noise filters------for noise & ripple-free pure DC. Capacitors are found everywhere for different reasons and purposes. Even the big power supply capacitors, although fairly large in size (about the size of a Campbell's Chunky Soup can) are rated a fraction of one made 1-Farad + or more. A Farad is a fairly large rating.


Edit: typo. Got to start using spellcheck!

['Doc]

... and just to stir the pot a little bit...
Audio is AC. Primary power to most mobile radios is DC. Big difference in a capacitor's actions between AC and DC, what happens with one probably won't happen with the other. DC electricity characteristics are pretty 'straight forward'. AC electricity characteristics get sort of 'weird'. The audio form of AC get's really 'weird'. (Just take a look at some of them 'audiophiles'. Now that's weird!)
- 'Doc

(Yeah, I know, but I couldn't resist. All puns intended.)

[BIGHOG]

What a great thread! I have been into high performance automotive, as well as car audio my whole life. But after reading all this I am still undecided. I have 2 one fard capacitors sitting on the bench at home. It is mighty tempting to throw those rascals inline about 12" before my DM. What do yall think go/no go?

['Doc]

I'm not going to re-read this thread to see if it's been mentioned so this may be a 'dupe'.

If you want to use a large capacitor, be my guest. There are a couple of things you really should keep in mind though. They have very little to do with electronics but have a lot to do with health and wealth.
Large capacitors are very dangerous. They tend to explode, not 'pop', when over excited. They tend to get 'over excited' at the most inconvenient times. Need to get a 'jump start', or maybe give one? Better disconnect those caps or you WILL regret it. That's because of something called a voltage surge. Happens almost every time with a 'jump start'. Ever hear about the precaution of selecting a capacitor with a voltage rating 2 ot 3 times the voltage applied to it? That isn't enough 'precaution' with a capacitor of 1 farad, 10 times isn't all that cautious either. But it's your... ah, neck, and insurance.
Ever shorted out a small capacitor and see the spark? Odds are that little thingy was maybe a one hundred thousandth of a farad or smaller. Part of that 'spark' was you seeing some electrons 'flash' through air. Another part of that 'spark' was vaporized metal from where that cap shorted against something. Now think of 100,000 time that amount of vaporized metal hitting whatever is near it. Maybe in an engine compartment, in your trunk maybe, under the dash and near your feet? How much would you bet that I'm exaggerating? Wanna make me your insurance beneficiary?? The only joke in that is about the beneficiary thing. But after very careful consideration, I'd still take it.
- 'Doc

[BIGHOG]

I here ya doc. I used to work in the radio industry a little and have had to bleed off very large caps before walking into transmitter rooms. Man I used to hate doing that. Talk about sh&^%%ing yourself! They will suprise you!

[lucas]

i had a huge sound system in my car a few weeks back (till i sold it), 1200 watts for the subs plus 600 watts for the 4 speakers, the "cap" i found very very USE LESS!, my lights still dimmed, voltage meter was all over the place with the beat of the music. your asking well was the right wire used, grounded right. Wire used on the sub amp was 1/0 gauge and 4 gauge use on the 4 channel (speakers) amp, grounded stright to the frame, and then re ran to the battery. The big three was done, new battery installed ect.ect, my opinion of the "CAP" is. it's just a big old bandaid for weak charging systems.
The best advice if your pushing some heavy beef (amps) like me still (lots of lights on the front of my car , do the big three. 1) alternator positive to battery positive, 2) battery negative to chassis, and 3) engine ground to chassis. A new battery might be in order, more so if its been killed a few times. replace the alternator with some thing more beefy if need be.

[WESTGATE]

i use one in the mobile on my 5 pill.....its a 50 farad, with the engine on the truck generates 14.4 volts, with AC and headlights on at night drops down to 14.1-14 volts....the capacitor will help in keeping the voltage up and steady to give u better output , i feel it was useful but my setup would run good without it also.....hook ur radio up to it also ...help keep the voltage up on that too and get more watts into the amp,

randy

['Doc]

"50 farad"... really?

Just did a search and they really do make such a thing, amazing! Guess I should have done that search first instead of after, right?
Still couldn't find a voltage rating for it, so you won't ever see one in my car. That is ridiculous.
- 'Doc

[WESTGATE]

lol....its rated at 20 working volts-24 surge volts.....ive used it off a 200 amp,20 volt unregulated supply before....worked fine

['Doc]

Good for you! I hope your luck stays that good.
- 'Doc