Capacitor or Red top?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=50361
Printed Date: July 07, 2025 at 11:45 AM
Topic: Capacitor or Red top?
Posted By: xb2002
Subject: Capacitor or Red top?
Date Posted: February 18, 2005 at 12:28 AM
I have had a pair of hx2 dual 2ohm in a 92 acura legend now for 2 years no problems with a kicker 360 (720rms i think)pushing them. When I installed the subs I ran 1/0 welding lead from the front battery positive to the rear battery positive(both red tops). I also ran a 12" 1/0 from front battery to strut tower, and rear to frame. I ran a #2 welding lead from my alt to my front battery positive, and the same size ground bolted to the alt. I had 3 other 8 gauge grounds to to header core on front end, firewall, and fender. In the trunk I used #2 welding leads and connected my amp directly to the battery. This setup gave me a good sounding loud system. I am new to capacitors. I just sold the car and I bought a T10001bd and a pair of P3's. I will be installing them into a 98 chrysler sebring. I am curious if a double battery setup like I had in the acura would be reliable in the Sebring?? I didnt have a isolator, nor a fuse. I am an automotive tchnician with 10yrs exp. I didnt install a fuse between batterys because of financial reasons at the time. I will not be playing the system longer than a minute or two at idle. So I guess my questions is caps???? or extra bateries???
Replies:
Posted By: kfr01
Date Posted: February 18, 2005 at 12:33 AM
New ho alt if anything. Extra batteries or caps would be a waste of money, imo.
------------- New Project: 2003 Pathfinder
Posted By: haemphyst
Date Posted: February 18, 2005 at 12:34 AM
Alternator FIRST, then battery, then if you got a couple hundred extra for bling, go for the cap... They do little to nothing for a properly set-up electrical system. Also, this time, put fuses in the leads! You are ASKING for a fire if something happens...
------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: xb2002
Date Posted: February 18, 2005 at 12:58 AM
Thanks for the suggestions. I have been around car audio for a long time. Just never worked at a stereo shop. Alt and batterys have always been the current supply upgrades. I guess I am just worried about frying my new amp by having a voltage drop. Theese capacitors seem to me just came out of no where!! All of a sudden shops are tring to sell you a $200 cap and a $200 install kit. lol Back in the day a guy in our town had the SPL world record with 16 15" subs, 4 Power 1000's 8 tractor batterys with 4 alternators...lol 4000 watts...Nowadays it's 4 15" with 16000 watts!!! My how have times changed!!!
Posted By: kfr01
Date Posted: February 18, 2005 at 1:14 AM
First, a temporary voltage drop isn't going to fry an amplifier. Second, an appropriately sized alternator will solve that problem for you.
Anyway, your observation is right - shops are pushing caps like crazy. The reason isn't their utility. The reason is rather the unfortunately successful misinformation by the sales people and relatively high profit margins.
------------- New Project: 2003 Pathfinder
Posted By: ull3030
Date Posted: February 18, 2005 at 1:16 AM
xb2002 wrote:
Thanks for the suggestions. I have been around car audio for a long time. Just never worked at a stereo shop. Alt and batterys have always been the current supply upgrades. I guess I am just worried about frying my new amp by having a voltage drop. Theese capacitors seem to me just came out of no where!! All of a sudden shops are tring to sell you a $200 cap and a $200 install kit. lol Back in the day a guy in our town had the SPL world record with 16 15" subs, 4 Power 1000's 8 tractor batterys with 4 alternators...lol 4000 watts...Nowadays it's 4 15" with 16000 watts!!! My how have times changed!!!
I remember in the 80's when it took at least 4- 15" subs to reach 140+ Db's now you can do it with one 12" -------------
Posted By: soundzplus
Date Posted: February 18, 2005 at 7:22 AM
ok --- Looks like some peeps NEED an education about the cars power and how it relates to car audio - - First of all - The hi-output alternator is an important part -- then you need reserve power also known as a battery - optima / stinger / whoevers battery then as the voltage travels down the power wire - it has a varying amount of AC ripple -soo by the time it gets to your amps it needs to be filtered - NOW - Heres where "that waste of Money" the cap comes in - 1: A cap filters AC ripple - 2: A cap can recharge the amps internal caps faster than the battery can and can recharge itself at a faster rate than any battery 3: This allows at hi volume the amplifier to maintain a constant stable power supply So - it might be a good idea to do the homework before decide
Posted By: DYohn
Date Posted: February 18, 2005 at 10:13 AM
soundzplus wrote:
ok --- NOW - Heres where "that waste of Money" the cap comes in - 1: A cap filters AC ripple - 2: A cap can recharge the amps internal caps faster than the battery can and can recharge itself at a faster rate than any battery 3: This allows at hi volume the amplifier to maintain a constant stable power supply
4. But ONLY if there is already enough voltage and current available from the alternator and battery to sustain the amplifier's normal demand AND to recharge the capacitor. ------------- Support the12volt.com
Posted By: soundzplus
Date Posted: February 18, 2005 at 11:17 AM
Last time i checked --- a capacitor doesnt need a hi-out put alternator to "Charge" caps .. So - anyone with any experience in Car audio -- or 12volt in general - should know this This is the "12volt.com" right ?... Just checkin
Posted By: oonikfraleyoo
Date Posted: February 18, 2005 at 11:50 AM
No a cap doesn't need a HO alternator to charge. But in that case while its charging it is drawing power away from your amps. A cap is not a cold fusion device. If the current is not already there, then a cap aint gonna put it there. ------------- Nik
Jeeputer Progress
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Check it out.
Posted By: haemphyst
Date Posted: February 18, 2005 at 12:48 PM
soundzplus wrote:
Last time i checked --- a capacitor doesnt need a hi-out put alternator to "Charge" caps .. So - anyone with any experience in Car audio -- or 12volt in general - should know this This is the "12volt.com" right ?... Just checkin
No, you are correct, a cap does not REQUIRE a HO alternator. BUT when a cap discharges for a loud beat of music, the remaining energy in that cap becomes a bit less. A cap, when connected to a power source (in this case the alternator/battery) will ALWAYS want to be fully charged, to it's maximum capacity in Joules. When a bass beat hits, SOME of the energy stored in the cap is used in the form of current, to supplement the POSSIBLE current sag from the battery. The cap WILL NEVER discharge all the way, which is, I think, a misconception some people have. It will then proceed to suck current from the alternator/battery FASTER than it put it out. This is a VERY short current drag (on the order of milliseconds, or even microseconds - it depends on how much current the battery can provide for this drain. Yes, I said battery, because it is a LOWER IMPEDANCE device than the alternator, also, electrochemical rather than electromechanical, so therefore faster), but the current peak can be HUNDREDS of amps, depending on how much energy was depleted from it during the bass hit. oonikfraleyoo wrote:
No a cap doesn't need a HO alternator to charge. But in that case while its charging it is drawing power away from your amps. A cap is not a cold fusion device. If the current is not already there, then a cap aint gonna put it there.
Please see the above note: Additionally, because the cap DOES recharge (but in milliseconds) almost immediately, there is little chance that your amplifier will notice the current gulp your cap is "stealing" from it for it's recharge cycle. And actually, if the current is not already there, THIS IS EXACTLY WHAT A CAP IT PUT THERE TO DO! Fill in the current sag from the primary source. Also while all this discharging/recharging is going on, the alternator has had time to START PRODUCING ENOUGH CURRENT to fill in all of the potential sags in the power stream. This is why, if your alternator cannot make enough current, it will make current until it reaches it's capability, make that amount of current until it can't anymore, due to thermal or mechanical stresses, and if it does NOT fail, the battery will discharge further and further, until the entire electrical system fails. This IS a worst-case scenario, but this is basically what can happen. (IMAGE DELETED. SEE MESSAGE BELOW) I drew this up to let people visualize what actually happens with your electrical system. This should be pretty easy for everybody to understand. Just imagine everything being at 14.4 pounds of pressure (or 14.4 VOLTS) and it is a closed system. You can see in this system what will happen if you allow your electrical system to be overloaded, and how the alternator and cap work, too... ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: oonikfraleyoo
Date Posted: February 18, 2005 at 12:55 PM
Show me a cap recharges in miliseconds. Most 1 farad caps recharge in 10 - 20 seconds, which is plenty of time to suck power away from your amps. ------------- Nik
Jeeputer Progress
[|||||||||||-] 90%
Check it out.
Posted By: haemphyst
Date Posted: February 18, 2005 at 1:30 PM
Yeah, a cap recharges through a resistor in 10 to 20 seconds, but there is no resistor in this circuit. It is connected DIRECTLY to the high gurrent source of the battery. Have you ever connected a dead cap to a battery, and you get that HUGE spark? That is the charging of that cap. You can do the math for yourself (maybe).
Here is a link for you to SEE FOR YOURSELF how fast a cap will recharge. I used a resistance of .006 ohms (a reasonable number for 10 feet of #4 cable, 1F is 1000000 microfarads (that's one million) and a voltage of 14.4 volts. The result was .006 seconds, or 6 MILLISECONDS at 2400 amps. And this is from a completely discharged state. A partially charged cap will recharge faster than that. even a 40F cap will reach full charge in .24 seconds. That's LESS than 1/4 of a second...
Still wanna help out? HUH?
:::Edit:::
Sorry for the tone... I don't like it when people question me... ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: DYohn
Date Posted: February 18, 2005 at 3:39 PM
haemphyst wrote:
Sorry for the tone... I don't like it when people question me...
Oh yea? Why not? :) Capcitors will attempt to resist any change in voltage by charging and discharging. The charge or discharge will happen instantaneously (in theory. It is limited by many things as described above.) Basic electrical theory. ------------- Support the12volt.com
Posted By: stevdart
Date Posted: February 18, 2005 at 4:15 PM
Hey haemphyst, I question your damn BIG drawing! (Do I need the widescreen model?) lol
Posted By: haemphyst
Date Posted: February 18, 2005 at 4:41 PM
somebody shrunk my pic... bwahahaha Sorry about the "big picture". It's tough to scale down from a 21 inch LCD monitor. DYohn, if you want to delete the one above, here is a better copy - more suited for 1024x768 monitors, without the loss of reolution.
Try this one on for size... ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: ty
Date Posted: February 19, 2005 at 3:37 AM
great analogy haemphyst.
Posted By: xb2002
Date Posted: March 02, 2005 at 6:03 PM
I have decided to go with a upgraded alternator. The recipitent for the system is a 98 Sebring. It has a mitisubishi alternator in it , and my local alt shop said he can double it from 90-180amps. I plan to do this and use my red top. My new question is how many caps should I use and what farads? t10001bd, 2 P3's Coustic 460 on highs.
Posted By: forbidden
Date Posted: March 02, 2005 at 6:43 PM
At this point in time, no caps at all. You have no idea until the system is installed if you need them or not. Read the grounding stickies first, this will give you some very good info to follow first. ------------- Top Secret, I can tell you but then my wife will kill me.
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