Capacitors FAQ
What they do, and when to use one
Q: What's a capacitor?
A: A capacitor, or cap, is an electronic component that can take up, store, and discharge electrical energy. Because they can do all that quickly, capacitors are used to filter or buffer any sudden changes in a circuit's voltage, smoothing the ensuing signal.
Q: What's a capacitor used for?
A: In car audio, large outboard capacitors, sometimes called stiffening caps, are used to prevent lights from dimming when loud bass notes play. They accomplish this by supplying the amplifier with a quick jolt of power.
Q: Even if my lights don't dim, won't a cap still improve my system's low end response and overall sound?
A: Not really. A cap prevents the sound from deteriorating due to under-voltage, but doesn't actually improve the sound. It supports the amplifier by feeding it the power it needs for short bursts. So, while not improving sound quality directly, a cap does make it easier for the amp to perform its best.
Q: What size cap should I get?
A: The rule of thumb is to put in 1 Farad of capacitance for every 1,000 watts RMS of total system power. But there is no electronic penalty for using larger value caps, and in fact, many see benefits with 2 or 3 Farads per 1,000 watts RMS. The larger the cap, the faster it gets ready for the amp's next big hit.
Get Everything You Need
Give your subwoofer amp the boost it needs with a capacitor. We also have all the installation hardware you need to get your capacitor and amplifier up and running.
Q: How do I hook up a capacitor?
A: If you don't have the instructions that came with your capacitor, you should know first off that a cap can be dangerous; it can charge and discharge so much power so very quickly that it can weld metal objects, like tools and jewelry, and melt its own insides out. A new cap comes completely discharged, so it's safe. A resistor or wired light bulb usually is included in the package. Wiring the bulb or resister across the cap's terminals allows the capacitor to discharge slowly and safely. The same bulb or resistor, wired differently, also gets used to charge up the cap safely.
As in all car electronic installations, start by disconnecting the ground cable from the car battery. In this installation, also take out the in-line fuse on the amp's power wire next to the battery.
A capacitor should be mounted as close to the sub amp as possible using the shortest wires possible. This is so the extra charge doesn't have far to go to get to the amp quickly. Make sure the cap gets mounted securely and won't become a dangerous flying object in the event of an accident.
A capacitor has two poles: a positive and a negative. They should be clearly marked on the capacitor. The positive connects to the same positive power lead that goes to your sub amp's positive, 12 volt, connection. Use the same gauge wire as the amp uses for its power. This can be accomplished with a distribution block. Or, sometimes, the cap comes with multiple connection terminals that make it easier to wire it into your system. The multiple terminals act just like a distribution block so, for instance, the power wire coming from your battery can connect directly to the cap's positive terminal while a short cable connects from there to the amp's positive power connection. The negative pole of the capacitor connects to your chassis ground, just like the amp. The best practice is to use the same bolt the amp uses for ground. Make sure all the paint is scraped off around where you put the chassis ground and the connections are clean and tight.
Next, you need to charge up your capacitor. If done too quickly — it could "pop," destroy the cap.
If you don't have the original charging/discharging resistor or light, you'll need to get one. An automotive 12-volt test light, the kind with a bulb, not a small LED, will do nicely. Otherwise, you can use a high-wattage, low resistance resistor, available at most electronics parts stores. The exact value doesn't matter, but get one with a value of 10-1,000 ohms along with a rating of 1-20 watts. The lower the resistance, the higher the wattage should be.
Take the test light or resistor and connect it to the two terminals of the amp's in-line fuse holder (where you took the fuse out earlier). Re-connect the car battery's ground cable. The resistor will get hot, or the bulb will light up, while the cap charges. After 10 to 30 minutes, the bulb will fade out, or the resistor will start to cool. Remove the light or resistor carefully — they can get very hot. As you replace the fuse, you may experience a small spark — that's okay, but should remind you of how powerful the electric forces involved are. Your capacitor is now installed.
Q: My cap has a third terminal. What's that for?
A: Some caps come with a built-in meter that displays the voltage. If a meter were to stay on constantly, it could drain the car's battery. So caps with meters often have a remote turn-on lead connection, just like car amplifiers, so the meter turns off with the system. A thin, 18-ga. or so, wire should run from the cap's turn-on connection to the amplifier's remote turn-on terminal, or any other switched 12 volt power source.
T-Spec 3.0-farad capacitor
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Johnathan McClendon from West Point
Posted on 10/9/2019I have a dark audio dki 10 wired to 1 ohm and a audiopipe APMI 1500. My interior lights and license plate tags are dimming, I have led headlights so I can't tell if they are dimming or not. What size capacitor would you recommend? Or should I upgrade battery under the hood? My car is a 2018 Toyota Camry SE.
Buck Pomerantz from Crutchfield on 10/10/2019Jonathan, The rule of thumb is to put in 1 Farad of capacitance for every 1,000 watts RMS of total system power. But there is no electronic penalty for using larger value caps. For more info on curing light-dimming, check out this article.Jason from Aurora
Posted on 10/5/2019Would it not be wise to install an adequately sized diode on the 12v+ line before it connects to a capacitor; so other accessories dont, sap the power from the cap, basically isolating it to the subs ?
Buck Pomerantz from Crutchfield on 10/5/2019Jason, I don't think a high-current diode on the positive power lead will do anything to prevent an accessory from drawing current from the vehicle's electrical system. A diode regulates polarity, blocking out positive or negative voltages depending on its installation. No polarity change occurs when an accessory draws current from the system, so installing a diode is like solving a problem that doesn't exist.Tiaan van Niekerk from Johannesburg
Posted on 9/30/2019Would a capacitor remove alternator whine from my old amp?
Buck Pomerantz from Crutchfield on 10/1/2019Tiaan, That kind of noise is usually caused by a loose ground or power connection. A capacitor will have no effect on the noise.Imran patel from GUJARAT, INDIA
Posted on 8/24/2019Hi I have 2.4 farad capasitor. Manufacture date on the Package is of 2014 but it is never used and is in fully packed condition. is it safe to use this capasitor after this long period ? Or should i skip it?? Thanks in advance
Buck Pomerantz from Crutchfield on 8/26/2019Imran, An unused capacitor stored correctly should work okay. But to be sure, you could check with the manufacturer.John Brannon from Valdosta
Posted on 7/30/2019I have a 2018 kia optima I have 2 12s with a 900 watt amp an a cap here recently my system has been going in and out an i watch my cap i can see the digits go up and down and then they go blank what causes that ive checked my wires an connections??
Buck Pomerantz from Crutchfield on 8/1/2019John, Your hybrid vehicle's electrical system probably can't support that strong of an amplifier. Crutchfield recommends installing amps only up to 350 watts RMS in such vehicles.Daniel from Wixom
Posted on 7/3/2019Hi Buck, in my 2014 Ford Taurus SHO with the factory Sony surround system, I am experiencing my sub not hitting nearly as hard when I have the volume turned up. I am going to purchase a single farad cap for my 250 watt Kicker DX. I am concerned that my factory Ford Sync system will fool the cap to not trigger the "auto turn-off" feature, thus draining my battery. Have you experienced this on any of the new infotainment systems?
Buck Pomerantz from Crutchfield on 7/3/2019Daniel, I've heard of issues with amps not turning off immediately after the car is turned off, but I doubt a capacitor would cause more trouble in that situation. The amp would be draining the battery more than the cap.Ivan from Chicago
Posted on 7/2/2019I have a 2011 Cadillac CTS Wagon and installed 2 JL Audio 12TW3-D4 with JL Audio JX1000/1D at 1 OHM. I hooked it up to the factory Bose subwoofer connection and eliminated the Bose subwoofer. The interior lights dim when the bass hits. Would you recommend a specific cap for this?
Buck Pomerantz from Crutchfield on 7/3/2019Ivan, You didn't say whether or not you've removed the factory Bose subwoofer amplifier, so your vehicle could now have two amps firing up whenever bass is called for - and maybe that's the issue. Also, that JL Audio amplifier is not stable for powering a 1-ohm load, and is probably drawing crazy amounts of current trying to do so. The only safe way that amp and subs should get wired together is like this.karzi from kask
Posted on 6/28/2019hey, i have a question about my capacitor , had my system installed on my old car it was working so fine , before i sold it , i removed the amps , capacitor and forget to discharge the cap , when i bought a new car i installed it again , but i found that its draining my battery, should i get a new capacitor ?
Buck Pomerantz from Crutchfield on 7/1/2019Karzi, Try running your system without a capacitor. Maybe you don't need one. But if your headlights then dim on big bass hits, replace it.Jordan Bae from Middletown
Posted on 4/13/20191 capacitor for for 2 mv500s and a old Sony Xmas-3060 or one for each?
Buck Pomerantz from Crutchfield on 4/15/2019Jordan, A cap works best when installed near the subwoofer amp. Try one capacitor, at first, and if that doesn't stop light-dimming, then install a second.Lady J from Atlanta,GA
Posted on 4/1/2019I have 2 audio pipe amps with 1500 watts one for the mids and one for the subs. I just recently bought a 1200 watt capacitor and when I play the sound my bass does not hit at all and when I turn the volume up to 15 my sound goes in and out on the left side. Could it be that the capacitor watts are too low and I need to put another 1200 watts with it? I need help please
Buck Pomerantz from Crutchfield on 4/1/2019Lady, Capacitors are rated in Farads, not watts, so I'm not sure what you have. I suggest removing the capacitor from your system and seeing if the drop-out problem goes away. If it does, the cap was the cause. If not, then you'll have to continue troubleshooting until you find out what's killing the sound. I'd start with the wiring and then make sure the amp gains are set properly.-
DustinC from Fairfax,VT
Posted on 3/31/2019I recently purchased a Alpine mv-500 wired to a 2ohm dvc kivker03cvr154 15in, when I changed boxes I noticed the sub was only wired to 1 voice coil, and it use to dim my lights VERY NOTICIBLY, I re wired the sub to 4ohm for the new box and have allot less dimming now, was wiring it to 1 voice coil actually a 2ohm final and drawing more power? I've read many articles saying it's fine to wire to 1 voice coil of a dvc speaker. But can't find ANYTHING about what that makes my impedance. I'm trying to get closer to the factory speaker specs as possible and it's not a 1ohm stable amplifier.
Buck Pomerantz from Crutchfield on 4/1/2019 Dustin, It is not okay to wire only one of a pair of voice coils. When you only wire one of a dual voice coil sub's coils, you split its power-handling ability in half, threatening to burn the sub out, and increase its distortion, because the sub has to push around the dead weight of the disconnected coil. In your case, the amp was seeing 2 ohms. You are right to wire the coils together in series to make a 4-ohm total load. Neil Lizotte from Edmonton
Posted on 3/11/2019What would a good price be for a 18 volts 1000 farrads capacitor made with graphene and no heat or battery management issues?
Buck Pomerantz from Crutchfield on 3/13/2019 Neil, Not only can I not find such a device for sale, I wouldn't exactly know a reason for using such a large capacitor. Rob Duchene from Cape Coral
Posted on 2/17/2019I own a 2016 Dodge Challenger Scat Pack. I've read the stock alternator is rated at 220A. I'm unsure how much is needed for vehicle operation. My plan is to power 2 Kicker S12L7 with a Precision Power Black ICE 7000.1D ran at 1 ohm final. How do I correctly calculate expected current draw to figure out if I can add a capacitor or if I will require upgrading the alternator? (I'm hoping to avoid the latter) Thank you
Buck Pomerantz from Crutchfield on 2/18/2019 Rob, The rule of thumb is that 50% of an alternator's output is available for aftermarket electronics. The way you figure your amp's draw is as follows. The amp is rated to put out 2300 watts RMS at 1-ohm. In order to do so, the (let's say) 80% efficient amp needs 2875 watts RMS from the car's power supply. 2875 watts divided by 13.8 volts equals 208A. Assuming you're playing music not tones - loud bass music has a duty factor (how often full power is called for) of 40%, so your car's electrical would have to be able to support a constant draw of 83A. Fuzzybarrel4563 from San Leandro
Posted on 1/22/2019Are capacitors used only in subwoofer applications or can they be applied to a full range amplifier running the door speakers?
Buck Pomerantz from Crutchfield on 1/24/2019 Fuzzy, Capacitors are usually used with subwoofer amplifiers because those amps draw substantially more power, in bursts, than full-range amplifiers do playing music steadily. But it won't hurt anything to use a cap with another kind of amp. David Peterman from Chesapeake
Posted on 11/19/2018Ive got a 04 hyundai elantra stock battery stock alternator. I was using a 500w rockford and memphis set up in my jeep with barely any noticeable problems( lights dimming) but im afraid with the smaller battery in the Elantra and the fact im also wanting to install a set of 4 Rockford speakers with 400w amp im going to be using to much power. I was thinking about getting a bigger battery and installing a 1farad cap. I figured 1farad would be fine considering i have 900 total rms watts. My question is there should be no problems with a speaker and sub system sharing a cap is there? Is there a problem with putting my cap under the hood if im going to put the amps under both front seats? Caps are suppose to be as close to amps as possible so is that to far? Thank you guys
Buck Pomerantz from Crutchfield on 11/20/2018 David, You should never install a capacitor under the hood, where engine heat could destroy it. A cap really only does any good when wired near the subwoofer amplifier. Brandon
Posted on 10/16/2018I have a 2001 F250 and the engine pulls so much of the batteries to turn over that the head unit starts and resets whenever I start the truck. The whole system goes in and out of protect mode while driving. I assume the issue is the current draw for the system from the batteries, but should 4 65W infinity speakers run off a 704a amp cause an issue like this? If it's just the electrical draw, a capacitor should help right?
Buck Pomerantz from Crutchfield on 10/16/2018 Brandon, That amplifier should not be taxing your vehicle's electrical system at all, and the symptoms you describe don't sound amp-related, but more likely a wiring issue. Check the batteries and all wiring and make sure every connection is tight and electrically solid. If you bought your gear at Crutchfield, you could call Tech Support for free help troubleshooting your system. Their toll-free number is on your invoice. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Click on this link for details. Daniel Larson from Hurricane
Posted on 10/9/2018Can I use a trickle charger to charge the cap?
Buck Pomerantz from Crutchfield on 10/10/2018 Daniel, I think that's a bad idea. A trickle charger would send the cap 12 volts instantly, which could cause damage. Use the resistor or light bulb that came with the cap to charge it up when it's installed. Jack Bhakta from San Antonio
Posted on 9/28/2018I am going to be using a small 200 watt 2 channel MTX sub amp to a 300w rms 10" sub in a sealed box. Currently, my lights dim EVEN with the factory audio system, when I hold up my power window switch after the window is shut. The stock alternator is only 1 year old, and puts out only 80 amps, but an upgraded one with 130 amps can be installed. Can I save money and parts by just using an existing functional old 0.5 farad capacitor, to help buffer the load and premature wear on my car's electrical charging system?
Buck Pomerantz from Crutchfield on 9/28/2018 Jack, A 200-watt amplifier shouldn't tax your factory electrical system. Obviously, holding a window button up does. I doubt a capacitor will help. Normy from Carson
Posted on 9/5/2018Good afternoon. Question I am running cxa 1200.1 amp to kicker 10L7 in custom tune box. Will I need a capacitor
Buck Pomerantz from Crutchfield on 9/7/2018 Normy, You shouldn't even consider installing a capacitor until you experience light-dimming when the bass hits - then a capacitor might help. Melissa Taylor from Canistota
Posted on 9/4/2018Do I have to run to remote wires one to the amp and another to the capacitor? Or can I one and splice it
Buck Pomerantz from Crutchfield on 9/7/2018 Melissa, You can "daisy chain" the remote connections, running a single wire from the receiver to the amp, then another wire from there to your cap. William from Highspire
Posted on 7/21/2018I got a 12" kicker it's 1500 watts Max is 2500 was thinking about getting a 2000 watt amp what would be a good capacitor to get for it
Buck Pomerantz from Crutchfield on 7/21/2018 William, For capacitors, we recommend at least one Farad per 1,000 watts RMS of amp power. In your case, check out the T-Spec 3-Farad cap. Satan's Helper from Waterboro
Posted on 7/21/2018I currently have a Sub box with two 12" Kicker subs and a Skar Audio 1000w amp. I haven't hooked anything up yet. I'm also planning on purchasing 4 Kicker door speakers and another Skar Audio 1000w amp. One will be a mono block (which I have), one a A/B (which I want). My question is with this setup, can I run two amps off one huge capacitor or do I need two capacitors to two amps? I'm thinking an 8 or 10 Farad would be more than sufficient. Thank you.
Buck Pomerantz from Crutchfield on 7/21/2018 Satan, Capacitors are usually just wired to the subwoofer amplifier, where they do the most good. It's loud bass beats that eat up energy. Joshua Essig from Glenwood
Posted on 7/18/2018Your instructions say to ground the amp and the capacitor to the same point. I have always been told to ground the capacitor at a different point. I plan on two 1000 watt amps and two 1.5 F caps. Should I be... A) grounding all 4 wires to 1 point. B) grounding amps to caps like parallel speakers then 2 cap grounds to 1 point, or C) amps to 1 ground point and caps to a separate ground point not inline with audio equipment grounds?
Buck Pomerantz from Crutchfield on 7/19/2018 Joshua, The reason most techs say to ground all devices at the same point is to avoid potential differences in current flow that could create a noisy ground loop. Your other proposed grounding schemes may work out just fine, though. Kevin nieto from Los Angeles
Posted on 6/5/2018I have a small set up which is: Rockford Fosgate 801S Rockford Fosgate Punch Power 250.2 2x kicker comp VR 12" The 250 is powering all of my mid and tweeters 801s subwoofers. The lights do dim slightly with this set up will I need a capacitor?
Buck Pomerantz from Crutchfield on 6/6/2018 Kevin, Start by checking all power and ground connections and then the battery itself. Then, if you still experience dimming, you can consider adding a capacitor or another electrical system upgrade. Check out How to give your car's electrical system a power-up for help with that. Buck Pomerantz from Crutchfield
Posted on 6/1/2018Mike, I don't know that a capacitor would do any good in your situation. I'd more likely look into getting a higher-output alternator.
Mike from Freehold
Posted on 5/19/2018I was looking at using a capacitor in my racecar that uses a small lithium battery. I have a good amount of electronics in the car. Problem is I have a 30amp electronic shift solenoid that controls and shifts my sequential dog box (manual transmission) and currently the lights dim and voltage drops during every shift which also effects my fuel/ timing tuning. Would I be able to use an audio capacitor and wire it in as if the shift solenoid was an amp or is there a better solution. A larger battery is not an option due to space constraints.. Would a capacitor help?
Buck Pomerantz from Crutchfield
Posted on 4/18/2018Shawn, Usually, capacitors are used in high-power systems to ensure constant power supply voltage. I doubt a 5.7-watt system would ever need a capacitor. But maybe I'm misunderstanding. Not knowing what your system consists of makes it impossible to give advice about it.
Shawn Kahn from San Jose
Posted on 4/18/2018Great article Buck. I have a slightly different setup that is been discussed here. I have a ClassD amplifier driving max power of 30W speaker with an average power close to 7.5W. I have 1uF capacitance to support the 24V rail. Does 1F per 1000W rule of thumb applies here. Is there a way to calculate exact needed capacitance based of system parameters? Thanks
Buck Pomerantz from Crutchfield
Posted on 3/26/2018Rick, For the short wire runs on a motorcycle, I doubt you'd notice any difference.
Rick Bice from Zanesville
Posted on 3/24/2018I am hooking up a sound system on a Yamaha motorcycle with the watt amp in the fairing. The battery is under the seat. There is no room for a capacitor anywhere else but in a saddlebags. My questions is can I just run a + and - 4 age wire to the battery and get the same benefit as having the capacitor right next to the amp?
Buck Pomerantz from Crutchfield
Posted on 2/21/2018Tomas, You are correct - the wire terminals for the T-Spec 3.0 Farad capacitor fit 8- to 4-gauge wire. The good news is that a few feet of 4-gauge wire is not expensive.
Tomas from Lamar
Posted on 2/20/2018My amp's 1/0 power and grounding cables look too large to fit in Crutchfield's 3.0 farad capacitor. I'm not sure if my eyes are fooling me, but if they aren't, how can I make this capacitor fit into my system without getting different power cables?
steve carey from Richfield
Posted on 1/19/2018how do i hook my capacitor and amp when the amp has [ +cap ] [12vpower] [grd] [ -cap] [remote]
Buck Pomerantz from Crutchfield
Posted on 1/2/2018Alex, A capacitor can potentially charge up instantaneously, and then explode. A capacitor should be charged up using a resistor or light bulb, so that it charges up slowly and safely. That procedure doesn't take more than 5 to 30 seconds to accomplish.
Alex Bainter from Puyallup
Posted on 1/2/2018How fast can a 2000 watt 2 farad capacitor charge?
Buck Pomerantz from Crutchfield
Posted on 12/15/2017Bradley, Every capacitor has an ESR (equivalent series resistance) factor that will act like a small drain on a battery over time. A great solution for you is to get a battery maintainer, like a RetroSound Exile EX-1 Battery Keeper.
Buck Pomerantz from Crutchfield
Posted on 12/15/2017Brad, That amplifier shouldn't go into protect mode at those voltages. It sounds like something's wrong with the amp and it needs repair or replacement.
Bradley
Posted on 12/15/2017Hi, I know you've had a thousand variations of the same question. I've read a bit and thanks for the responses. As I understand when it comes to the capacitor charge when the car is off it is like a part of the battery. So excluding any bad wiring or parasitic draws it can maintain the charge so long as the battery is fine. For instance, my car battery can go 2 months when I'm away for work when my family neglects to crank it over like I ask. So in essence the cap isn't drawing and will stay charged with the battery as long as they're attached properly? I get double checking the cap would be wise after that long to be safe. I have a bluetooth OBDII that has a tiny drain but has never killed my battery. Is the capacitor causing a drain, but one that is so nominal like the bluetooth dongle it's almost certainly another issue if the capacitor and battery is dead when I get back? I will run from the rear deepcycle battery a fuse rated below the the proper gauge wire but above what is necessary for the amps to a 3 farad cap to a two fuse block each fuse sized for each amp. The cap and 2 way will be right beside both 1500 watt amps.
Brad Keys from St Thomas, USVI
Posted on 11/11/2017I have a Rockford fosgate amp that keeps going into protection mode only when I increase engine rpm. I've red it could be due to my vehicle voltage regulator going bad. The voltage at the amp is around 13.5- 14 depending on rpm. Could a capacitor give my amp a more appropriateand co start voltage so it doesn't keep going into protection? Thanks
Buck Pomerantz from Crutchfield
Posted on 10/16/2017N, The size wire to use is totally dependent on the size of the amplifier, not whether a distribution block or capacitor is in the circuit. If your amp requires 1/0-gauge wire, then use that throughout the installation.
N. McClaughry from Greeneville
Posted on 10/15/2017I have a T spec cap. In this article you state it's like a distribution block so would it be okay to run 0 gauge to the cap then 4 gauge to the amp?
Buck Pomerantz from Crutchfield
Posted on 9/30/2017Tomas, First off, two DVC 2-ohm subs can only get wired together to form a 0.5-ohm load, a 2-ohm load, or an 8-ohm load. The good news is that that amplifier puts out 2400 watts RMS at 2-ohms as well as 1-ohm. A capacitor smooths out power fluctuations due to a bass amplifier drawing more current than the vehicle's system can provide. If your lights dim when the bass hits hard, a capacitor may solve the issue. It should be connected at the bass amplifier's power connections to be effective. The "rules of thumb" about a cap's size is just a general pointer for getting the right product. In your case this 3-Farad cap should be fine.
Tomas
Posted on 9/29/2017Are capacitors as necessary for lower power speakers and amps as they are for high power subs and mono amps? The gameplan for my bass is to run two Alpine SWR-12D2 (1000W RMS) subwoofers in parallel at 1 ohm impedance stability, supplied by a Kicker 44KXA2400x1 mono amp (2400W RMS at 1 ohm stability). Using the aforementioned standard you listed, I got a 3 farad capacitor to start out with for my subs. (So I'm wondering how many more farads I should wire to my subs' amp for a highly efficient draw in my car's electrical.) I also plan on getting a pair of Pioneer TS-A6996R A-Series 6x9s (100W RMS, 4 ohms) on a Alpine PDX-F4 amp (100W RMS, 4 ohms) to cover my mids and highs as well as some woofer supplementation. Do I need to account for and include capacitors for the power of this segment of my system; and is it because of the power my subs' amp will draw that I must? What kind of total farad count am I looking at? With this power should I follow the 2-3 farads per 1000W more than the 1 farad to 1000W?
Buck Pomerantz from Crutchfield
Posted on 9/28/2017Junior, When a discharged capacitor is directly connected to a 12-volt source, it will charge up so quickly it could explode. Use the resister or bulb that came with your cap to safely, and slowly, recharge it during installation.
Junior from Chicago
Posted on 9/27/2017I disconnected my subs amp and cap this summer and wanted to reconnect do I need to charge my capacitor again?
Buck Pomerantz from Crutchfield
Posted on 9/25/2017Kev, Did you use a resister or lightbulb when you started charging your capacitor? If not, the cap may have suffered damage while charging too quickly. If you bought your capacitor from Crutchfield, you could call Tech Support for free help troubleshooting your system. Their toll-free number is on your invoice. If you purchased your cap elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Click on this link for details.
Kev
Posted on 9/25/2017I hooked up my cap just as described in the article which is the way I've always installed caps but for some reason the cap won't charge it just blinks and says "LO" and it's been charging for while.... can you explain what's going on ad what I. Have to do??...
Buck Pomerantz from Crutchfield
Posted on 9/12/2017Adam, I don't know exactly what's in your system, but in car audio, ignition noise is often caused by a loose or inadequate ground or power wire connection. If something in your vehicle's system is radiating RF interference that your transceiver is picking up, I doubt a capacitor will alleviate the issue. I think there're RF filters made to clear up these kinds of problems, but you'll have to check with a ham radio dealership for more information. I think calling an amplifier linear merely means that the signal out is the same as the signal in, only larger. In ham radio circles they call a clean, non-distorting RF amplifier a linear amplifier. In the car and home audio worlds, they call a clean, non-distorting audio frequency amplifier an amplifier with a linear response. I don't think there's any difference in meanings.
Adam from Seattle, WA
Posted on 9/12/2017I scanned the Q&A here and don't think this question has been asked. I'm a ham radio enthusiast as well as an audio enthusiast. I have installed an 11 meter transceiver radio in my car - operates in the 27MHz frequency range. It picks up some noise from somewhere when my 2013 Malibu is running. When the car is off, the noise goes away. I was wondering, would a capacitor help with this? Currently I transmit a max of 20-watts using battery voltage but would need it to be able to handle up to 500 watts radiated power. Finally, can you explain the difference between a linear amplifier (used in radio transmitting) and an audio amplifier?
Buck Pomerantz from Crutchfield
Posted on 8/16/2017Kristian, Coming onto an American web site and disparaging the standard measuring system won't get you much useful advice. Nor will not providing the make and model of the amplifier you're ultimately asking about. Just like me, you can use Google to translate American Wire Gauge sizes to metric dimensions. Check out our Amplifier wire gauge chart for help finding the right size power and ground wires for your amplifier.
Kristian N
Posted on 8/16/2017Great article and wonderful comments section! I have a 3.0 F capacitor which I want to connect to my new stereo and I'd like to get everything done at the same time, so I'm looking for a wiring kit online. It seems nearly impossible, however, to find out how thick a power supply wire I need to hook it up. The sub and amp don't actually need a cap, because it's a slim-fit 150W (50 W nom.) model, but just for the sake of argument: Is 10 mm² enough? Or do I need 20, 25, or even 50 mm²? (Please spare me the AWG scale, what's up with that?) Regards, Kristian
Buck Pomerantz from Crutchfield
Posted on 7/15/2017Mario, The size of a inline fuse in a car audio power supply is dependent on the size of the power wire and how much current (amplifier power) it's expected to safely carry. A capacitor's size has nothing to do with that.
Mario from Sacramento
Posted on 7/14/2017I have a 4 farad cap, how many amps should the in line fuse be?
Buck Pomerantz from Crutchfield
Posted on 7/10/2017Rudi, A capacitor should get wired to a constantly-on 12 volt circuit, so once it's installed it's always "on" and charged. The only time you'd need to discharge a capacitor is when you uninstall it.
Rudi Oosthuizen from Johannesburg,ZAR
Posted on 7/8/2017hi i wanted to know if i need to charge my cap with the given resistor every time i go out to use my sound, and same discharge it completely ever time I come Home or not in use? Is there a automatic way of connecting it to discharge or do i have to do it manually every time?
Buck Pomerantz from Crutchfield
Posted on 6/27/2017Jay, What you're proposing is extremely dangerous. Let's say your system can draw up to 250 amperes and requires 1/0-gauge wiring. If the capacitor in such a system were to discharge, boosting the amp's power input, a 4-gauge ground wire might melt or burn because of the high current.
Jay from Yuma, AZ
Posted on 6/27/2017Regarding the gauge of the ground wire, you mention the power wire specifically should be the same gauge as the original power wire needed for the amp. this is fine. But does the ground really need to be 1/0 if the rest of the system is? I cannot see any use for such a heavy duty cable for a cap ground. Most of the electron flow is output to the amp, not to ground. Could you get away with using something like 4awg or even 8awg for a cap ground even if the rest of your system used a larger gauge?
Buck Pomerantz from Crutchfield
Posted on 6/25/2017Eric, You've raised an interesting question about wiring multiple capacitors together. The resulting capacitance of two caps wired together behave exactly opposite of how resistors and coils work. When two capacitors are wired in parallel, you simply add their capacitance values (farads) together to get the total. When you wire two equal-size capacitors in series, the total capacitance is one-half the value of a single cap. To improve the performance of a capacitor used for car audio, wire the second cap in parallel with the first, increasing the capacitance. Parallel means wiring components together positive-to-positive, and negative-to-negative, if you're not sure.
Eric from Bartlett NH
Posted on 6/24/2017Is iit possible to run caps in series or is there any benefit to that?
Buck Pomerantz from Crutchfield
Posted on 6/9/2017Mike, Once a capacitor is installed, it becomes part of the car's charging system and doesn't need to get disconnected for vehicle maintenance. When jump starting a dead electrical system, after the starting motor gets things going, the alternator should slowly recharge the battery and cap safely.
Mike M from Wilmington NC
Posted on 6/9/2017Does a cap need to be disconnected before doing routine service on the vehicle and if the vehicle battery dies (lights on etc.) will the cap blow upon jumpstarting?
Buck Pomerantz from Crutchfield
Posted on 6/6/2017Steve, I believe car battery voltage can sometimes surge to as much as 14.8 volts. If your capacitor was designed to be used in an automotive electrical system, it'll be alright.
Steve from Black Creek
Posted on 6/5/2017Will a capacitor with both a working voltage and surge voltage rating of 12-14 volts be ok? Doeasnt a car's voltage sometimes go over 14 volts with the engine running above idle and/or chargeing the battery?
Buck Pomerantz from Crutchfield
Posted on 4/14/2017Mike, Yes, you can wire your capacitor without a distribution block as you describe.
Mike from Dickinson
Posted on 4/13/2017I'm installing a capacitor do I need a distribution block or can I wire battery to the capacitor and then off the capacitor to the amp on the 12v + side of it
Buck Pomerantz from Crutchfield
Posted on 4/12/2017Shay, For playing music, I think that your high-output alternator ought to support your system using a single battery and no cap. If you're competing by playing loud bass burps, however, you may need the second battery and capacitor.
Shay from Telford PA
Posted on 4/12/2017Hello. Great article. I have 2 JL 1000/1 amps powering 2 JL 12W7s, 2 JL 300/4 amps powering 8 6.5 JL 5 Series door speakers. Total system power is currently 2600 watts, but the 2 JL 300/4s are gonna be upgraded to JL 600/4 because the door speakers can handle more than the current 75 watts they are getting. So, system power will eventually be at 3200 watts. I just ordered an overpowered XS power D6500 battery and I currently have an Ohio Generator Alt cranking 320 amps installed. My question is this, should I use the XS Power battery as a secondary battery and not install my Stinger 505 Cap, or use that XS Power battery as the main battery for the entire vehicle and use the Cap? Any other advice would be great as well! Thanks a lot!
Buck Pomerantz from Crutchfield
Posted on 3/13/2017Novice, A capacitor could hold its charge and possibly be dangerous. To make sure it's not, discharge it. Touch the two conductors of a wired light bulb or resistor (20 ohms, 10 watts for example) across the cap's terminals to discharge it slowly and safely.
Novice
Posted on 3/12/2017I used a rockford 1.0 farad cap in my car audio setup for years. I disconnected and uninstalled everything a few years ago and recently stumled upon the capacitor. May be a silly question--but better safe than sorry... is this thing dangerous? Does it still hold a charge? Does it need to be discharged? A friend of mine wanted it but I am afraid to give it away for risk of injury.
Buck Pomerantz from Crutchfield
Posted on 3/3/2017Aldrin, If you are trying to run a Skar Audio LP-1000.1D from a 10-amp battery charger, you will find it won't work. That amp will try to draw up to 90 amperes of current which that system can't provide. All adding a battery would do would be to drain the battery along with the charger. If you want to use that amp at home you'll need a 12-14 volt DC power supply (not a charger) capable of supporting a 90-amp draw.
Aldrin Ibarra from Cheonan, South Korea
Posted on 3/3/2017Hi...! I have a lp1000.1d hooked in a 10amp (15amp max) battery charger as an audio set up in my workplace... Problem is that the battery charger can't provide enough power for the amplifier when it hits bass notes... Can a 2f capacitor directly connected (in parallel) between the battery charger and the amplifier solve the problem...? I don't consider using a battery because it's very heavy... I can't either buy a high current DC supply because it's very expensive... I hope you can help me with this... Thank you...
Buck Pomerantz from Crutchfield
Posted on 3/3/2017Ben, Most people use a distribution block to wire the positive power leads of multiple devices in a system. But if your capacitor has room in its terminal system for a low-current device like an LOC, then it's probably alright to use it.
Ben Kramper from overland park ks
Posted on 3/2/2017Do i put the power cord from my LOC onto the positive terminal of the capacitor also?
Buck Pomerantz from Crutchfield
Posted on 2/20/2017Jim, Rebooting when first powering up is a normal function of a lot of receivers - it's a way for the internal computer to operate properly. I've never heard of using capacitors in the manner you describe for the reasons you state. If you want your receiver powered continuously, you'll have to use a separate battery.
Jim from Mount Airy, MD
Posted on 2/18/2017My touchscreen head unit reboots when I start the car. Installing two 2200uF capacitors (in parallel) to the red ACC wire (in series with a 1A diode) keeps the head unit on for about 10 seconds after switching the ignition off, but it still reboots when cranking, presumably because the starter causes a voltage drop. How much capacitance is appropriate for the yellow continuous power wire?
Buck Pomerantz from Crutchfield
Posted on 2/10/2017Herb, A capacitor helps when a vehicle's lights dim along with loud music, so unless you're in that situation, there's no benefit in adding one.
Herb from Vienna
Posted on 2/9/2017Should I use a cap even if I'm running 0awg power wire on 1000 watts
Buck Pomerantz from Crutchfield
Posted on 2/8/2017Dee, I'm only familiar with using an automotive capacitor to smooth out voltage fluctuations of an amplifier's power supplied by the vehicle's electrical system. I really can't tell you if a capacitor will be of any use for a fuel pump - or three. And the use of 60A relays along with 20A fuses is confusing - as is the need for filtering the power supply of a pump.
Deejaydque from NSW Australia
Posted on 2/8/2017Hi, I have a retro fitting situation for a 8 farad cap. Car audios will benefit from a cap in some instances. My question is, could i use the cap to assist with high current draws from high flowing fuel pumps in my vehicle that draws alot of current/voltage? I have 3x high flowing fuel pumps currently hired wired with 3x 60A relays to 3x 20A fuses to a power distribution box then direct wired to the battery. I want to install the 8F Cap in-between the power distribution box --> to the + battery terminal. Will the cap work in this situation and are there any dangers/factors in this retro fit?
Buck Pomerantz from Crutchfield
Posted on 1/23/2017Dan, I don't know what speed is normal for your particular capacitor, but the load provided by the multimeter itself will drain the voltage from the capacitor. And charging and discharging a capacitor repeatedly while out of circuit will eventually wear it out.
Dan from Canada from Brandon
Posted on 1/21/2017Hi Buck I was charging my 1 farad capacitor with a resistor. The led display and my multimeter were showimg different voltages while charging. Then at 12V charge and nothing hooked up but the test leads, meter was showing voltage drop 4-5 volts in one minute. Is that a sign of a bad cap? Thanks
David from England
Posted on 1/19/2017Thanks a lot Buck, much appreciated. I've removed the cap from the system now!
Buck Pomerantz from Crutchfield
Posted on 1/19/2017David, Capacitors are usually used in 12-volt applications to provide a quick jolt of energy to a subwoofer amplifier so a vehicle's charging system, the alternator, can catch up with a voltage drain due to the amp's current demand. Think of one like a spring that provides a lift, but then needs to get squeezed back together again for re-charging. If a capacitor has its power removed and is still connected to an amp (in circuit), it will slowly discharge. Whether that would be enough to actually turn the amp on for a little while - I don't know. Charging and discharging caps quickly is what kills them. I really don't see any benefit in using a capacitor in the manner you describe.
David from England
Posted on 1/18/2017Hi, I'm using a 1 Farad cap in a portable 12v sound system, which can run on a 12v battery or a computer power supply unit. So when not in use the psu or battery is disconnected from the system. On the two amps I'm using a jumper between remote and pos to turn them on when I hook up the power source. I have two questions, firstly will the cap act as battery and provide power to turn on the amps (and drain the cap) when the power source is totally removed? And secondly, when I remove the power source will the cap drain and is this bad? I appreciate any help, thanks
Buck Pomerantz from Crutchfield
Posted on 12/30/2016Slu, Not really. A cap prevents the sound from deteriorating due to under-voltage, but doesn't actually improve the sound or energize the battery. It supports the amplifier by feeding it the power it needs for short bursts.
Slu from lusikisiki
Posted on 12/30/2016The capacitor can help to automatically stop the music when the battery becomes low ?
Buck Pomerantz from Crutchfield
Posted on 12/16/2016Rixon, Like the article states, the rule of thumb is to put in 1 Farad of capacitance for every 1,000 watts RMS of total system power, but there is no electronic penalty for using larger value caps. In your case, with a less-than 1,000 watts RMS of amplifier power, a 1- or 1.5-Farad capacitor will do.
Rixon from Abudhabi
Posted on 12/15/2016I have JBL ms15sd2,1800watts 450watts RMS.2 ohms .and Alpine MRV M 500 amp so which will be suitable capacitor for my system...?
Buck Pomerantz from Crutchfield
Posted on 11/22/2016Matt, An intermittent power connection, one that turns on and off a lot, can definitely contribute to a capacitor's destruction.
Matt from Burrillville
Posted on 11/22/2016I've got a capacitor hooked up between my battery w/ fuse and a chassis ground, it's supplying power to my amp. It has worked for years with this setup, but recently my car's battery connector came loose and a few days prior to being able to tighten it with a wrench I was just jiggling it by hand to make the connection and get the car started. Still getting around 14.5V measured at the battery terminals, but my cap no longer charges to the battery's voltage. It peaks around 9V and shuts off. The toyota battery connectors are old and need to be replaced anyway, but could an inconsistent battery connection have ruined the cap?
Buck Pomerantz from Crutchfield
Posted on 11/3/2016Neil, The total RMS wattage of a system is simply the sum of the RMS wattages of all the channels. For example, the total power of a system consisting of a 50 watts RMS per channel 4-channel amp for speakers plus a 500 watts RMS sub amp is 700 watts RMS. (50 x 4) + 500 = 700.
Neil from South
Posted on 11/3/2016Hey, Please can you tell me the formula for calculating the RMS of total system power? Thanks
Buck Pomerantz from Crutchfield
Posted on 10/18/2016Justin, In the event of light-dimming when the music hits in a system, even one without a sub amp, a capacitor can often help maintain smooth power flow for an amp's power supply.
Justin
Posted on 10/18/2016Can or should one be used with an amp that's only going to drive speakers and not subs?
Buck Pomerantz from Crutchfield
Posted on 9/27/2016D, Capacitors can work in many different applications to smooth power supply fluctuations or to filter out certain frequencies in a signal's flow. In car audio, a cap usually is called for in systems of over 750 watts RMS output power. If you think your CB radio amplifier is drawing too much power from your vehicle's electrical system, you can connect a cap between its positive power wire and ground just like it was an audio amp to ensure smooth 12-volt power flow.
D from nevada
Posted on 9/26/2016can a cap be used other than car stereo equipment ? such as cb radio amps ?
Buck Pomerantz from Crutchfield
Posted on 9/19/2016Now, A capacitor needs to be always connected between constant 12 volt positive and ground, not a switched source of power. As soon as the battery gets disconnected, the cap will start to drain. Instead of wishing that a cap manufacturer will accommodate your misuse of their product, you should find out the source of your parasitic drain and fix that, or use a battery charger to maintain the system's charge when in storage. Otherwise you're stuck using that resister to slowly recharge your cap every time you switch the batteries on, or risk damaging it.
Now hear this
Posted on 9/19/2016Buck, if I may follow up to my first question, the cap is not losing its charge while the batteries are connected. It's losing its charge because as you know there are parasitic things that steal current all the time. My head unit is one of them. Even when it is off it is stealing a tiny bit of current (probably to maintain some settings). This is what discharges the capacitor eventually when we don't drive the thing for a while. And I know this happens to other guys who have some toys they don't drive that often. What the capacitor manufacturers should do is put in an input current limiter for when the voltage is real low then allow full current flow once the voltage goes beyond 8-9 volts. That would protect the capacitor no matter what anybody did with it.
Buck Pomerantz from Crutchfield
Posted on 9/19/2016Now, A capacitor should stay charged to the same voltage as the battery it's connected to. If your cap loses its charge while the batteries maintain theirs, the cap is defective. Or, it isn't connected correctly: between constant 12 volt positive and ground.
Now hear this
Posted on 9/17/2016I have a 800 RMS subwoofer amp installed in a recreational vehicle. I have a dual battery setup where there is the standard starting battery and then I put in a big marine deep cycle battery to run the amplifiers. The battery cable runs to the amps are quite long in comparison to a car. I have 2 gauge cables though that seem to be doing fine. I noticed that the sub bass was not quite as clear and crisp as I thought it should be so I bought a 18 farad capacitor and installed it right at the subwoofer amp. Immediately noticed that the punch of the sub bass was much tighter and cleaner. My only problem now is that we only occasionally use this vehicle and I've blown out the capacitor a couple times which I think is occurring because it is discharging completely over time and when I turn the battery switches on it is probably causing too much current flow. I had to put in the battery switches because otherwise both batteries would always be dead when we went to use it. The battery switches stopped that problem. Is there a way other than disconnecting the capacitor each time and using that little resistor to charge it that the capacitor can be protected from these initial current spikes that seem to be killing it? A relay? A choke?
Buck Pomerantz from Crutchfield
Posted on 9/7/2016Edward, Check out this how-to article for help tuning your subs.
edward coolz from daphne
Posted on 9/7/2016hey buck i have 3 1ohm powerbass 12s running a 1000 watt audiopipe to them they sound very good and im more than impressed with the bass im getting.. my question is what are some pointers on how should my amp settings should be i have the hardest time getting my amp tuned just write what are some simple steps or do u kno the readings i can set them amp..
Buck Pomerantz from Crutchfield
Posted on 9/6/2016Brian, You're right, a capacitor electrically connects to all parts of the positive power wiring. It's restorative effects, however, are best felt by the amplifier that's closest to it.
Brian from Idaho
Posted on 9/6/2016I've studied Crutchfield's amplifier (and cap) installation diagram, available at Crutchfiled.com. I see the cap + is connected to a + distribution block which provides + to two amps. By using a distribution block this way doesn't the cap actually provide support for both amplifiers, equally? I have three amps all tied into a single + dist block. If I were to add a cap via that + dist block, would all three amps get cap support (and I should size my cap accordingly, correct?).
Buck Pomerantz from Crutchfield
Posted on 8/22/2016Christian, Even when your car is "off," the battery will keep the capacitor charged. The cap is, I guess, technically "on," it has a charge, but it isn't doing any work (passing current while discharging and recharging). In effect, the capacitor is an extension of the battery itself, charged and ready for work when the switch is thrown.
christian quiroz from riyadh
Posted on 8/21/2016i have a question? when i put a capacitor wired direct to battery (+ to +) then ground, my question is, how about when you the car is off, the capacitor is still on? or also automatically off when you off the car? thanks
Buck Pomerantz from Crutchfield
Posted on 8/8/2016S, You got me on a misspelling. Thanks for the catch.
S
Posted on 8/7/2016dialectic??? (7/25/2015) Might want to look up the definition of "dialectic" then look up "dielectric."
Buck Pomerantz from Crutchfield
Posted on 7/12/2016Anthony, I'm not at all sure that a capacitor suitable for smoothing out voltage fluctuations due to an audio amplifier's power usage will work the same way for the autopilot motors in your boat. I guess in theory it could work, but without any idea of the duty cycle or current draw of the system make figuring out the proper cap size virtually impossible. I suggest you contact the manufacturer of your boat or autopilot and ask their tech department if a capacitor would work in your situation, and if so how big should it be.
Buck Pomerantz from Crutchfield
Posted on 7/12/2016Thomas, A capacitor is supposed to be "on" and fully charged up at all times, whether the amp or car is on or not. After all, if it's installed correctly, it connects to a constantly-powered 12-volt power line and ground. The remote lead on some caps is to turn the volt-meter or some other feature on and off, not the cap itself.
Anthony Dragani from Swampscott
Posted on 7/12/2016Hey I could use some guidance. I have a sailboat with an autopilot that is effectively an inductive load (DC motor pulses on and motor turns clockwise or counterclockwise to steer boat on course). The problem is I can see the voltage drop when the motor pulses on. My instruments don't like the resulting voltage drop. I think a cap would compensate for the inductive load and provide the current spike without drawing the voltage down. I would like to have the cap discharge when I leave my boat for safety reasons. So I would to charge it when I turn instruments on. I am trying to find out the motor spec. s to find out how much instant current it needs for each pulse. I think I may be looking at an amp at 12 volts but that is WAG. What would work for me size cap with charging and discharging included? Or what do I need to look for in picking one?
Thomas Murphy from Lonoke
Posted on 7/12/2016What if your cap does not have a remote terminal, but still comes on when fuse is hooked up as apposed to when ignition is turned on and powered up like the amp does? The amp comes on when the key is turned on, but the cap is acting like it has a constant power and turns on as soon as I install the inline fuse...
Buck Pomerantz from Crutchfield
Posted on 7/11/2016Dan, Alternator whine or engine noise is indicative of a bad ground, or a defective head unit or amplifier, or a radiating electrical system, and usually has nothing to do with a capacitor. If you bought your gear from Crutchfield, you could call Tech Support for free help troubleshooting your system. Their toll-free number would be on your invoice. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Click on this link for details.
Dan from Austin
Posted on 7/8/2016Hi, I have an RF 1 F capacitor off the battery that splits the power line to an Infiniti Basslink powered sub and an RF 4 channel amp that feeds 4 speakers. I get a lot of alternator whine and noise in the audio. I've checked all the grounds and they all look good (short runs, solid contact to chassis, paint sanded off). I had the polyfuse in the Pioneer HU replaced because I had hot-swapped the RCA cables in the past, and the RCA cables are all new. Could the cap be a cause of the signal noise?
Buck Pomerantz from Crutchfield
Posted on 7/3/2016Scott, Like the article says, the rule of thumb is to put in 1 Farad of capacitance for every 1,000 watts RMS of total system power. But there is no electronic penalty for using larger value caps, and in fact, many see benefits with 2 or 3 Farads per 1,000 watts RMS. The larger the cap, the faster it gets ready for the amp's next big hit. For you, if your amp truly is 2400 watts RMS and that wasn't a peak number you quoted, a 3.0 Farad T-Spec capacitor will work well.
scott
Posted on 7/1/2016i got 2 12" subs and a 2400w mono amp and was wondering how big of a cap would be recommended for it to perform properly and not drain my battery dead also was wondering what a cap brand makes a really high quality cap thats gonna be reliable and has a good capacity
Buck Pomerantz from Crutchfield
Posted on 6/6/2016Joey, I suspect those astronomical power ratings you mention are peak amplifier ratings, which should not be used when planning systems. The rule of thumb for capacitors is to have 1 Farad of capacitance for every 1000 watts RMS of amp power. Your 3.5 Farad cap can handle a 3,500 watts RMS system. If yours is indeed larger, then get a new larger cap, if you need one at all.
Joey
Posted on 6/5/2016Hey I got a 3.5 farad cap and it was for my one 15" sub atm I'm only using a 1,400 watt amp, I want to upgrade my system with 2, 4k watt 15" subs/amp and 2 8" subs with a 600-800 watt amp. Can I get another cap at like 4 or 6 farads and put them in a series or should I just outright buy a bigger one?
Buck Pomerantz from Crutchfield
Posted on 6/3/2016Norman, A tech with T-Spec told me that the volt meter on their capacitors can sense current flow and turn on when the engine is on, and slowly turns off when the engine's off. Maybe your capacitor works differently. I wouldn't think any reputable capacitor manufacturer would put out a product that would drain and possibly damage a car battery.
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