[old_skool_noma]

and you don't have to use a battery isolator anyways. it's just recommended if you like to sit with the truck not running but still listen to your stereo for a long period of time.

that is if your batteries are the same type and age though, amirite? otherwise one will always try to charge the other and that leads to premature failure IIRC.

 

[juddspaintballs]

in theory, yes. if you're using similar batteries and neither one of them is trashed, you're not going to see any real change. batteries never reach an equilibrium anyways, so some current is always flowing.

 

[ryanroberts]

what up guys im new 2 the site.i read a bit of what was said.im pleased 2 hear good information on here .i want 2 add a few things. there is new amplifiers without a turn on lead. they signal sense from the rcas.just like a powered homesub.but they are usually on the highly efficient digital amplifiers.and electrolytic caps can b usefull beyond just tightening up bass at higher volumes,they can make your amplifiers last alot longer by smoothing out the ripple in the current.but a better option are audio batteries.which have a low esr like a cap(esr meaning discharge rate or electro series resistance)and r usually equivelent 2 about 50 1 farad caps. but they also store alot more power like a battery.which means more crankin amps and parkin lot listenin time! its also nice because ur power wire runs 2 ur amp will b substantially shorter. but take precaution when wiring a second battery. u will need a fuse within 12 inches of ur starting battery,and a fuse at the + input of ur secondary battery.u will also want to have a fuse at the + output of ur secondary battery on the wires running 2 the amps.fuse size 4 the 2 fuses between starting and secondary battery can b up 2 100 amp with agu glass fuses.it doesnt matter if they seem oversized 4 ur particular amp. because there only theire in case of a catastrophic dead short in ur main power wire.trust me if u short a power wire2 ground. u could blow a 500 amp fuse easy. and ur vehicle would b saved from burning 2 tha ground.the fuse at ur secondary battery before ur amp should match the amperage rating of the fuses on the amp.i hope this helped. hopefully it didnt just confuse everyone

 

[ryanroberts]

also wanted 2 add.make sure when u replace a bad battery have ur alternater checked and vice versa. usually if bad one will make the other bad. and dont think ur being ridiculouse for using large power wire. its better 2 be safe than sorry. u dont want substantial voltage drops. because then u pull much more current! especially with amps that have regulated power supplies. i have seen some run at 9 volts.with out 2 much degredation of sound.but they were pulling 120 amps.and make sure both batteries batteries are well grounded.with equivelant wire size. if u have 2 run a ground from starting battery 2 secondary battery!

 

[ryanroberts]

i posted the two comments 2 try and help people who may not know much about audio.or power.dont worry car audio isnt nearly as confusing or complicated as some make it seem.i have been an installer for 14 years and if basic rules r followed we rarely have issues. i can appreciate technical knowledge.but sometimes 2 much of it and 2 little realworld application. tends 2 turn people into the skeptical glass half empty type.car audio is fun and doesnt screw ur car up.if done properly!

 

[DCsdime16]

i'm soory to bother you, but am currently putting a lot of work into my dime, and can't risk a fire, now i'm not going for huge bump yet, i'm just putting in a kenwood kac-820 (1988) and two kicker comp 8's 4ohm, will i need to upgrade the big three for this set-up?

 

[bobditts]

i'm soory to bother you, but am currently putting a lot of work into my dime, and can't risk a fire, now i'm not going for huge bump yet, i'm just putting in a kenwood kac-820 (1988) and two kicker comp 8's 4ohm, will i need to upgrade the big three for this set-up?

it wont hurt.

what does this question have to do with capacitors?

 

[DCsdime16]

well he mentioned the big three upgrade so i was just asking, it won't hurt to not run the upgrade?

 

[Speedy2222]

big 3 can only help. the only thing that could be harmful is you are stupid enough to run smaller wire than stock... THEN you will have problems

 

[[email protected]]

WOW! What a blast from the past! I know that most high quality amps have ample capacitance when the system is right, but most aren't right. A battery is like a bucket with a hole in it than is leaking faster than you are filling it when you don't have the right charging system....... you just make the bucket bigger..... The cool thing about a cap is the ability to run cooling fans for amp racks without introducing noise.

You guys will think I am completely crazy, but the best use I found for a cap is on the factory power block(fuse block?). Once tied in with a diode, the dash lights, gauges, ECU's and anything else that may be sensitive to voltage drops behave much better

 

[DJDAudio]

WOW! What a blast from the past! I know that most high quality amps have ample capacitance when the system is right, but most aren't right. A battery is like a bucket with a hole in it than is leaking faster than you are filling it when you don't have the right charging system....... you just make the bucket bigger..... The cool thing about a cap is the ability to run cooling fans for amp racks without introducing noise.

You guys will think I am completely crazy, but the best use I found for a cap is on the factory power block(fuse block?). Once tied in with a diode, the dash lights, gauges, ECU's and anything else that may be sensitive to voltage drops behave much better

You know what, a cap installed after an inline Diode at the main fuse block for the ECU and so on would do the trick, hmm never thought of that! Would have to be at least a 100amp Diode, it would cause a 0.6VDC volt drop, but not much to notice I am sure.

 

[juddspaintballs]

I've seen a couple people put capacitors right before the headlights before. That helped with their dimming issues noticeably, but didn't really change voltage drop over the entire system. You just didn't see the headlights dimming, which is a "fix" for most people.

 

[[email protected]]

It really added to the life of those cheapo halogen bulbs that all my customers thought only came in 100 watt versions........:haha: We used the Jacobs accuvolt on a couple of crazy installs. Those things were the step up/ voltage regulators that would take any voltage above 9.5 volts and convert it to a user adjustable 13.5-16 or so volts...... they were dead stable, but have been discontinued. We didn't see any real difference between that and that cap/diode trick. All of our alternators were set at 14.4 anyway, so the voltage drop wasn't a big deal. The Alumapro piece was our first choice.

These things turned out to work as line conditioners..... The occasional mystery pops and ticks would just go away

 

[DJ KEW]

THANK YOU FOR THIS THREAD!!! Im so sick of trying to tell people what you just explained!!

That is all,
Keith aka DjKeW

 

[Five7s10]

good to know

 

[reelfish92]

 

[DJDAudio]

I have a few problems with that video. I will try to cover more of them this evening when I get home but one thing comes to mind,

Rload * C >> 1 / f

---------------------------------------------------------------
Rload = the total resistance of the load as seen by the alternator/battery
C = value of capacitor in Farads
f = the ripple frequency ( The frequency of the rectified 3Phase from the alternator)

This means that you need to size your capacitor depending on the overall load on the system, being that this 'load' is ever changing in an automotive audio environment, I can see some problems cropping up.

This is often why there are no capacitors on the DC 'rail' in the Car, most manufactures just assume that the DC rail in the car will be noisy, so they often Diode block filter capacitors inside the devices power supply, for the load on the system is known and often fixed within the device so the above can be factored.

For example if you where to put a capacitor for power factor correction on your house, your power bill would skyrocket, for you are now fixing the power factor problems of the entire neighborhood that is on your transformer, so you are being charged for the current passing because of your cap bank trying to smooth everyone.

This is why almost all system designers build a cap bank within their own device. Rule 101 of electronic design, assume your power is noisy. :haha:

 

[DJDAudio]

So I setup a very quick example in the lab last night,

The Setup,

* CLASS D Automotive amplifier.
* Regulated DC power supply. ( Almost completely ripple free )
* Non regulated Automotive power simulator ( Rectified 3Phase AC to DC )
* 1/3F Non pulse ratted Electrolytic capacitor
* Signal generator

The capacitor was diode isolated so the current going to charge the cap only could be measured.

NOTE: the cap will only discharge when the supply voltage is pulled below what is stored in the cap, and the cap will only charge when the supply voltage is greater than what is on the cap.

This means you will only see a current draw ( green) when the cap is 're charging'

The red voltage scale is the the fluctuation from the 14.4v baseline.
NOTE: the red Voltage line has been inverted to allow better measurement between spikes. This means as the voltage is pulled down the red line will go UP.

So first up here is the best case scenario, this is a 14.4VDC Regulated power supply. Almost perfect ripple free with very close to zero noise on the line. ( nothing like you would find in an automotive environment.)

See how the cap will only charge when the amp is not pulling power, this means a nice smooth load on the alternator. and if you add the both together, little to no ripple will be generated.

This is the 'ideal' lab world where almost everyone does there formulas and 'theory' So in this environment yes the cap would work great!

But..... :haha:

The real world is full of noise.
Here is my un regulated 14.4VDC automotive power simulator.

Look how the cap is following along with the amp draw.
Also look how much more current is being pulled by the cap. the reason for this? non filtered rectified 3Phase is not pure DC it is pulsed DC, and the cap is now trying to smooth out the power supply as well as power the amp.

In this setup the cap is now acting as an additional load in the system.

for the above to work you would have to know on a micro second to microsecond basis what the load on the system is as well as the current voltage and resistance, and they dynamically vary the capacitance, to keep things on track like the above Regulated system.

I hope this helps illustrate why this is such a heated debate.

 

[beandip]

Thanks for the info Doug! a visual always helps bring the point across.

 

[Christianbazin]

Thank you to whoever stickies this nice write dear.