when installing a cap should i put a fuse between the battery and the cap and the cap and the amp (total of 2) or just the one from the battery to the cap? dunno if should cause more restriction before it gets to amp or if its safer dont want to have to buy another amp for a while. TIA

 

The fuse just needs to be at the battery. The amps, signal processors, etc. have their own fuses. Anything more than that is just jewelry for the install.

 

 

I recommend a fuse at the battery before the cap, and a fuse between the cap and amp. Some amps don't have internal fuses (Rockford Fosgate is an example). Don't think of fuses as jewelry. The fuse protects the wiring and other components in the car from damage from a short. With no fuse you run an increased risk of fire in the event of a short. I can't say how much increased the risk is, but it's better safe than sorry.

What I did in both cars was to run a fused distribution block after the cap, that covered my fusing issues and makes sure that I am safe.

Another reason for that extra fuse... That little $6 fuse can save your $120 capacitor.

 

Or your $$,$$$ car!!! hehehe

However, when we are talking about a fuse between the cap and the amp... it's a different story. I think it's impossible actually. A cap discharges with something like 10,000 amps. Last I checked they didn't make fuses quite THAT big! And LWillmann I have no idea how you think you are doing it..... you must be mistaken.

 

Simple: Battery, fuse, cap, amp.

Keep the fuse around 12-18in away from battery.

Mount the cap as close to the amp as possible.

 

I think you mean 12 inches or less.... the closer the better.

 

While it is true that a capacitor does discharge quickly, I don't know about the 10,000 amp rating you supplied, firebirdude.

The cap is designed to supply whatever voltage it has stored (usually around 14v in your average car) at whatever amperage the amplifier is requesting it. The cap doesn't deliver amps per se, it simply maintins a steady voltage for the amplifier.

My reasoning for the fuse between the cap and my amp, is because a dead short on the cap and it will leak it's innards into the car. I don't want that. So by fusing with whatever fuse the amp is rated for simply ensures that when there is a short and the amperage spikes due to the rapid discharge of the cap, the fuse blows before the cap does.

Since I have an amp in one of my cars that requires a 50amp fuse, I use a 50 amp fuse in the distribution block, and the same up front. That make sure that the fuse blows as early as possible in the event of a problem.

 

Check the lightning audio website. Click on "power" then cap.
http://www.lightningaudio.com/products/

Also, I couldn't find it on that website, but I'm almost positive Lightning audio recommends you DO NOT use a fuse between cap and amp. I think it says it on every package......

And I don't think a fuse would prevent the caps innards from leaking. A fuse DOES take time to blow. It's not going to prevent the initial short. And if the cap is leaking, it will continue to leak. Fuse blown or not.

 

I think you need to brush up on what an ampere is and what a capacitor actually does(it does not supply voltage). I started to type a reply, but it was getting to be so long and it looked like it was going to be a lot lot longer, that i figured it would be best if i just listed a link to where you can read up on it.

http://www.soundillusions.net/module...howpage&pid=43

 

I read the entire page that you linked to, and I have a few observations about it:

I was wrong about a dead short causing a capacitor to leak it's inards into the car. It will simply discharge REALLY FAST.

It was a long document, but I remember nothing about amperage in there. So are you saying that I am wrong when I say "The cap is designed to supply whatever voltage it has stored (usually around 14v in your average car) at whatever amperage the amplifier is requesting it. The cap doesn't deliver amps per se, it simply maintins a steady voltage for the amplifier."

You say that it does not supply voltage, but here is a quote directly from that page: "When using very large capacitors (1/2 farad or more) in your car, the capacitor partially discharges into the amplifier's power supply when the voltage from the alternator or battery starts to fall. Keep in mind that the discharge is only for a fraction of a second. The capacitor can not act like a battery. It only serves to fill in what would otherwise be very small dips in the supply voltage."

I don't see where I am wrong here, maybe I over simplified the explanation or something but my understanding of electricity tells me that the cap can't send more amperage (flow) than the amp is asking for since you can't flow 1000 gallons a minute through a small hose. The amp is basically a valve at one end of a pipe, as it requires more amperage it opens the valve more, the electrical system just flows at whatever rate the valve and fuses will allow (not taking the wire into account here). You can't put a pump at the opposite end of the line from the valve and force more water through it, the water will just sit there and eventually either the valve, the pump or the pipe will fail. And it does act to maintain a steady voltage by softening the voltage surges and supplementing the voltage in drop-off or brown-out conditions.

If you noticed, I said that I use a distribution block. Granted I have only one amp in the cap that I was speaking of at the time, I have intentions to add a second in the near future.

I ran power from the battery, to the cap, then from the cap to the distribution block, and from there to the amp. That way I can add another amp to the system and it can also take advantage of the cap.

This is directly from Lightning Audio's web site (tech support section): "If the capacitor is to be used in a multi-amp system, a power distribution block may be used between the capacitor and the amplifiers." Also, their site states that their caps can deliver up to 10,000 amps instantly. But just because it can doesn't mean that is does it all the time.

By putting a fuse in line between the cap and amp, he can then later swap the battery for a distribution block and be ready for a second, third or whatever amp. Much easier than having to go through a lot of effort to get to the cap (in my case the cap is hidden) and replace the power cable to run a distribution block.

I always engineer my systems with future upgradability in mind.

 

a capacitor and a battery are not the same. In some respects they are similar, but in others they are not. A battery is a voltage source a capacitor stores charge. each unit of charge is either present or it is not (ex.. a partially charged capacitor) a capacitor will lose the voltage across it after a time. This voltage across is not because it stores the voltage as much as storing a charge.

Voltage is known as Electromotive force and current always flows from high voltage to low voltage. Amperage is calculated by how much charge flows per unit of time. As you can already tell Voltage, current and charge are all inter related. When a capacitor is charged one farad of charge in a one farad capacitor is held as the potential difference across its plates and the voltage across the two plates would read as the ambient system voltage.
(here is the important part)
when a fuly charged capacitor is removed from a circut it still reads what the ambient voltage was at the time of removal. If you attach a small resistor across the terminals and take voltage readings as the capacitor discharges you will notice the voltage will drop. This Electromotive force must exist in order for the capacitor to discharge, but it isn't storing the Voltage it is storing the charge.

I don't know if i explained this very well so if you still have questions please feel free. If i can't explain it better i suppose i could bust out my Physice book or my EE books to try to explain it better.

I also have to comment on the fuse before the cap or after the cap thing. It really won't matter what side of the fuse block the capacitor is on since current flows from high potential to low potential the capacitor will indeed discharge and current will flow back up through the fuse block and out to the other amp if it is needed.

 

Oops i forgot to capitalize Farad. I meant no disrespect to the man it was named after....

 

The discharge rate of a capacitor is not based on the amperage demands of the amplifier. It is based on 2 things: the resistance of the load (amplifier) and the capacitance of the capacitor (=R*C). A capacitor can NOT supply current. Ask the top competitors on the DB Drag circuit who refuse to use capacitors. If they do use one it is a 15 farad capacitor, which has such a long time constant of discharge that they "simulate" current flow.

In my opinion all a capacitor is is a $120 solution to dimming headlights. They do not make more power available for your amplifier. Think about it.... Power equals Current * Voltage. The Voltage remains constant but the current goes down (since a capacitor cannot supply current) overall power goes down. This has been proven on the Db Drag circuit.