Is My Capacitor Bad???

[ECLIPSEGST25]

I drove to my boys house this weekend and looked at volts dropping by the minute. my car died on the highway. we changed the altonator and put a new optima battery. we ran it at night and saw the volts were at like 11.8 - 12.8. once we disconnected the cap the volts went up to 13.5. how can i check to see if my capacitor is bad?? i have a lot of guages and a big sterio system which i'm sure all of that draws a lot of power. what should i do? what test should i run??

 

[sk8shorty01]

try to leave the capacitor and amp hooked up, but unplug the woofers (therefore they are not drawing power). If your volts are still dropping then it is either a wiring problem (such as grounding out) or the cap has some sort of draw that it shouldnt (broken). I would try that out and see if your volts stay up, if so then it is probably the system is to strong for the alternator and you would need to go get a new upgraded one.

 

[ECLIPSEGST25]

how long do i do that for? have the system on but just unplug the subs? how does it ground out?

 

[DGajre777]

It is not that simple (as in your capacitor being bad).

How big is your system? How many amps? What is the total fuse rating?

Upgrading the battery was pointless. If you have a big system, you need a big alternator. The purpose of the battery is to start a car. If anything you should have bought a Optima yellow instead of a red.

Here is some info...

Current draw
How do you know how much current your new amplifier will need? Divide the RMS power rating of the amplifier (let's say 500 watts) by the amount of voltage your car's electrical system will produce — RMS/Voltage = Current Draw.1 The average automotive electrical system will produce about 13.8 volts and 60 amperes of current with the motor running. So, 500 watts divided by 13.8 volts equals 36.2 amperes — your new amp will require about 36 amperes of current draw from your car's electrical system to achieve optimum performance.

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With the engine off, current flows from the battery to the accessories. The alternator supplies nothing.

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When the engine is running, the alternator charges the battery and powers the accessories. As long as the accessories' current draw does not exceed the alternator's charging capacity, the battery does not supply current.

Most cars come from the factory with a charging system that is adequate for the vehicle's stock equipment — air conditioner, power windows, defogger, etc — and can provide a modest amount of extra capacity (30-40%). If you drive a small car, adding 36 additional amperes of current draw to a system that produces only about 60 amperes of current could be a significant extra burden, one that your stock electrical system might not be equipped to handle.

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A high-powered audio system can draw more current than the alternator is capable of producing. At this point, current flows from both the alternator and the battery to supply the vehicle's accessories and the audio system.

Power Supply
Understanding the electrical system of your car will help you determine how much additional electrical current you need. When the motor is started, the car's electrical burden shifts from the battery to the alternator. The alternator creates alternating electrical current (AC) that is "rectified" (changed) into direct current (DC). The DC current runs all the devices in the vehicle which require electricity. The alternator also recharges the car's battery.

If the vehicle's electrical power demands exceed the alternator's capacity to produce juice, then power will be pulled from the car's battery. If the alternator and battery combined cannot meet all the car's power needs, then the voltage available to power each electrical device is diminished. Diminished voltage means an increase in current, and current produces heat that may damage your stereo system.

http://www.crutchfieldadvisor.com/S-lAPY91nASg5/reviews/20030729/current_affairs.html?page=1


Basically, Get a bigger alternator or downgrade your amps, there is no other way around it. You system is sucking up more juice than your car can handle/supply. A capacitor will help in bass peaks to prevent juice being sucked out of your battery and the alternator, but it will not increase your volts. Personally, I wouldn't run a capacitor unless you had a problem with dimming headlights.

 

[sk8shorty01]

Basically, Get a bigger alternator or downgrade your amps, there is no other way around it. You system is sucking up more juice than your car can handle/supply. A capacitor will help in bass peaks to prevent juice being sucked out of your battery and the alternator, but it will not increase your volts. Personally, I wouldn't run a capacitor unless you had a problem with dimming headlights.

A capacitor helps to get the power to your amp with even hits every time. When you get a really fast beat (lets say 120 bpm) if you take a reading on SPL it will decrease in strength every consecutive hit. You need the cap to keep that juice flowing to the amp. Like i said before your alternator needs to be upgraded most likely, but you can test if the cap is draining your electrical system out by doing what i stated above. The alternator probably cannot handle the load that is required by the system you have and cannot get out enough power to keep both the engine and the amps running (also maintaining power at the same time) so it slowly drains down your system. Try the simple test, then upgrade the alternator if needed. A short in your system could drain your alternators power also.

 

[DGajre777]

A capacitor helps to get the power to your amp with even hits every time. When you get a really fast beat (lets say 120 bpm) if you take a reading on SPL it will decrease in strength every consecutive hit. You need the cap to keep that juice flowing to the amp. Like i said before your alternator needs to be upgraded most likely, but you can test if the cap is draining your electrical system out by doing what i stated above. The alternator probably cannot handle the load that is required by the system you have and cannot get out enough power to keep both the engine and the amps running (also maintaining power at the same time) so it slowly drains down your system. Try the simple test, then upgrade the alternator if needed. A short in your system could drain your alternators power also.

Agreed! But on a system that is being starved for current, the capacitor is an additional device that the battery and alternator has to provide current to. If you have a Class D amp with a 60 amp fuse, sure get a capacitor, because you are not straining the charging system. Diming headlights during bass peaks is a sign that a capacitor is needed. But if you have amplifiers totaling 150amps and then you add 2 capacitors, how can you expect the stock alternator to keep up? This is why I said, if you don't have dimming headllights, the charging system is fine and you don't need a cap.

 

[sk8shorty01]

Yes, ok that makes sense. Sorry i misunderstood what you were saying. I dont know why because i was thinking you meant something else by how it was worded above. Thanks for clearing that up for me, and I hope the thread starter can figure out what is going on with the system. Good luck

 

[ECLIPSEGST25]

here it is. i have
3.0 farad cap
800 watt 2 ch amp
250 watt 4 ch amp
2 12' 400 watt orion xtr speakers
2 pioneer 6 1/2
2 pioneer 6 x 9
4 300 watt tweeters
panasonic head unit
8 autometer guages
1 5" tach
radar
satelite radio
apexi rev/ speed meter
apexi safc II
apexi AVCR
both of my radiator fans fun all the time.
and at night all this plus
reverse guages
headlights
fog lights

were can i find a high output altonator?

 

[DGajre777]

here it is. i have
3.0 farad cap
800 watt 2 ch amp
250 watt 4 ch amp

both of my radiator fans fun all the time.

were can i find a high output altonator?

Why do you have a 3.0 farad capacitor for a 800 Watt AMP? The recommended farad is 1.0 for 1000Watts and 0.5farad for 500 Watts.

800 watt 2 ch amp, 250 watt 4 ch amp - Are these RMS? What are the fuse ratings on the amps? Look at the fuses and add up the numbers.

Is there a reason why you have radiator fans run all the time? You don't really need them at highway speeds.

Do a search for "high output alternator", I responded to many of those threads. One thing you have to be concerned about with a high output alternator is that while it might charge the battery on the highway, it might put out less output than the stock alternator at idle RPM. If you drive at 3000+ RPMs all the time, it will charge the battery. If you drive around at high with everything on, and your system blasting/booming, your battery will die and not be able to start the car because the alternator won't be able to charge it.

Yes, ok that makes sense. Sorry i misunderstood what you were saying. I dont know why because i was thinking you meant something else by how it was worded above. Thanks for clearing that up for me, and I hope the thread starter can figure out what is going on with the system. Good luck

No problem!

 

[ECLIPSEGST25]

the amps are rms. the 2 ch has 2 30amp fuses and the 4 ch amp has 1 30 amp fuse. my distribution block has 2 30 amp fuses. and my guages have like 3 more 30 amp fuses. i rewired the aftermarket fans when i took out my AC. i just figured the the bigger the farad the better it would be. so should i get a high out put alt? why do some people put more then 1 cap in their car? i'm also thinking about putting 2 more 6 1/2 speakers in the kick panels. do all those other guages i have suck up a lot of power?

 

[DGajre777]

the amps are rms. the 2 ch has 2 30amp fuses and the 4 ch amp has 1 30 amp fuse. my distribution block has 2 30 amp fuses. and my guages have like 3 more 30 amp fuses. i rewired the aftermarket fans when i took out my AC. i just figured the the bigger the farad the better it would be. so should i get a high out put alt? why do some people put more then 1 cap in their car? i'm also thinking about putting 2 more 6 1/2 speakers in the kick panels. do all those other guages i have suck up a lot of power?

One problem - Your distribution block has 2 x 30amp fuses, but your amps are 30amps and 2x30amps. You either need to get another distribution block with 3 x 30amp fuses or replace the 2ch 30 amp fuse with a 60 amp fuse.

So you have 30+30+30+30+30 = 150amps. You amps and gauges alone are basically trying to suck up about 75amps of juice from a 75amp alternator. This doesn't include power for the ECU and other things needed for the car to run.

Disconnect the audio system until you upgrade your alternator.

 

[sk8shorty01]

Buy the alternator and you should be fine. Just dont idle for long periods of time.

 

[ECLIPSEGST25]

i just put a new alt and optima battery in on saturday. i will change out the fuses to 60 amp ones. what about the cap? should i get a 2.0 farad or add another one.

 

[DGajre777]

i just put a new alt and optima battery in on saturday. i will change out the fuses to 60 amp ones. what about the cap? should i get a 2.0 farad or add another one.

For the 2 ch amp, get 1 60 amp fuse for the distribution block. Leave the other one at 30 since the 4 ch amp has a 30 amp fuse.

Another cap or 5 more won't make a difference. A capacitor is not an alternator. Your car needs more current, plain and simple. When you add more caps, it means your alternator will have to charge more caps when it can't charge the stuff you already have. You can't expect a 75amp alternator to push 130amps just because you have that much stuff in your car.

Your options:
1) Take audio stuff out/disconnect it or take the 3 gauges with 30amp fuses out.
2) Get a bigger alternator
That's it. Just 2 options. No way around it.

After you get a bigger alternator, you can get a 1 farad capacitor for the 800 watt sub amp. You don't need a capacitor on the 4 ch. amp.

Although you have 2 extra farads on your existing cap, it is taking up current to charge it up now, but when you get a bigger alternator, that might not be an issue.

 

[ECLIPSEGST25]

my cap goes to the distribution block and the powers up both amps. so should i get a smaller cap or hang on to this one?

 

[DGajre777]

Hang on to that one if you are getting a high output alternator.

 

[ECLIPSEGST25]

the other 30amp fuses i have are for like the autometer guage lights, and the neons under hte car which i only use for shows. how many amps should the new alt put out? so i won't mess anythin up at idle. i might not get the new alt for a while so should i get a smaller cap then?

 

[DGajre777]

the other 30amp fuses i have are for like the autometer guage lights, and the neons under hte car which i only use for shows. how many amps should the new alt put out? so i won't mess anythin up at idle. i might not get the new alt for a while so should i get a smaller cap then?

If you are not getting a bigger alternator for a while, disconnect all the audio stuff, neons and anything that you don't need the car to run. The 3 gauges running with 30 amp fuses each are using up the 30-40% reserve power of your alternator already, you don't have any room for extra stuff to hook up on your car.

A smaller cap will take less time to charge compared to the 3farad one, BUT that is not your problem. Your problem is that you have WAY to much stuff in your car with the stock alternator.

Plan better next time. I believe the alterstart high output alternators push out 135amps.

 

[ECLIPSEGST25]

i called alterstart and they can do 150 amp for $279.00. i'm gonna try to sell my alt and get that one. if i get it would i be able to keep all the stuff in my car and stay with my cap? i rather have it charge up a 1.0 or a 1.5 farad then to charge up a 3.0so even if it's hooked up but i'm not using it or have it on it still pulls current?. hey thanx for all your help.

 

[DGajre777]

Let us assume that your car takes about 50 amps of current to run.

Amp1 - 60 amp fuse
Amp2 - 30 amp fuse
Gauges - 90 amp fuse
Neon, autometer gauges etc - 40 amps (estimate)

All the stuff above takes about 110 amps of current from your stock alternator. Add 50 amps to run your car to the 110 and you need a 160amp alternator. This number assumes that the neon, autometer and all the other stuff takes 40 amps.

Downgrading to a 1 farad capacitor will be a little easy for the alternator because it won't have to charge up the extra 2 farads. It is up to you if you want to downgrade the cap.

 

[DGajre777]

Here you go! I found a 200Amp Stinger alternator in the classifieds for $700.
http://www.dsmtuners.com/classifieds/showproduct.php?product=45140

The seller is taking trades, you can get rid of your Apex'i AVCR and get a $50 Joe P or Hallman Pro boost controller.