capping on caps

[audioholic 5,000+ posts]

The diagrams are midleading for more than one reason. Its an 'example graph' that people take as a specific test, which leads to many false conclusions.

definitely not for my car, but just saying that you don't have to upgrade to solve your stated issue, and most people say UPGRADE battery before alternator
edit: truthfully, i have had very good experience with longevity out of factory batteries, 11 years from motorcraft, and 9 from whatever came in the infinity

Yes, if the car is brand new so the battery is as well, you aren't likely going to see people recommending a new batt. But how often does that situation occur? Its much more often a used car, an old batt, etc.
The idea of recommending upgrading the batt before the alt is simple, make the current system as efficienct as possible before worrying about upgrading the power source. Its the same idea as upgrading the big-3, to ensure your charging system is as efficient as possible to handle and maintain the greater load on it than it was originally designed to handle. If the batt is new, no prolly dont need to bother 'upgrading'... but I think you are saying you see this situation here alot, people saying to 'upgrade' an already new batt. That is not what is meant by saying to 'upgrade' your batt first. When we answer questions here, we sometimes have to assume to reader will use some common judgement and realize if his batt is already new, the 'upgrade your battery before your alt' comment doesn't really apply. Unless the system is excessively large.

Running a large stereo thru a relatively small batt, even with a huge alternator to create the power, will cook that poor little batt. Ive seen it, hell Ive done it. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif Its amazing how quickly you can run a 'stock' battery dry when pumping a few thousand watts worth of extra current through it regularly.

 

[dman4486 5,000+ posts]

The diagrams are midleading for more than one reason. Its an 'example graph' that people take as a specific test, which leads to many false conclusions.
Yes, if the car is brand new so the battery is as well, you aren't likely going to see people recommending a new batt. But how often does that situation occur? Its much more often a used car, an old batt, etc.

The idea of recommending upgrading the batt before the alt is simple, make the current system as efficienct as possible before worrying about upgrading the power source. Its the same idea as upgrading the big-3, to ensure your charging system is as efficient as possible to handle and maintain the greater load on it than it was originally designed to handle. If the batt is new, no prolly dont need to bother 'upgrading'... but I think you are saying you see this situation here alot, people saying to 'upgrade' an already new batt. That is not what is meant by saying to 'upgrade' your batt first. When we answer questions here, we sometimes have to assume to reader will use some common judgement and realize if his batt is already new, the 'upgrade your battery before your alt' comment doesn't really apply. Unless the system is excessively large.

Running a large stereo thru a relatively small batt, even with a huge alternator to create the power, will cook that poor little batt. Ive seen it, hell Ive done it. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif Its amazing how quickly you can run a 'stock' battery dry when pumping a few thousand watts worth of extra current through it regularly.

thanks....everything i have been trying to say plus some better explanation

 

[spoonraker 10+ year member]

I'm just referring to how the diagram is misleading, saying that the batt doesn't help until voltage drops to 12V, which is ridiculous. Many people don't realize that while their car is running, their 12V batt has a much higher voltage...

You are mistaken. When your car is running, the battery isn't the only source of electricity, the alternator is as well. The alternator produces current at a significantly higher voltage than the battery. Most alternators sit around 14.4 and most batteries around 12.7 when fully charged. The alternator is hooked to the same circuit as your battery, and if you remember basic electrical laws you would know that electricity always flows from the highest electrical potential to the lowest. In the case of your test, from your alternator to your DMM. So even though you might be probing your battery terminals, you are really just taking a reading of your alternator's voltage. This is why when you turn the car off the voltage returns to battery voltage, mid-upper 12s.

What a cap is supposed to do is keep the voltage above that of the battery's during a bass hit so that the battery doesn't take the load, however in reality the cap only takes the load for a fraction of a second and sort of eases the load onto the battery. However, the full load still almost immediately transfers to the battery, and you see almost no benefit.

 

[audioholic 5,000+ posts]

What a cap is supposed to do is keep the voltage above that of the battery's during a bass hit so that the battery doesn't take the load, however in reality the cap only takes the load for a fraction of a second and sort of eases the load onto the battery. However, the full load still almost immediately transfers to the battery, and you see almost no benefit.

System voltage will remain basically constant throughout the circuit, barring any excessive resistance. A cap's voltage is and will be the same as system voltage, including the batt.

 

[RAM_Designs 5,000+ posts]

You are mistaken. When your car is running, the battery isn't the only source of electricity, the alternator is as well.

Well no kidding, everyone knows the alt is the main source of power in the charging system. No one is debating that.

The alternator produces current at a significantly higher voltage than the battery. Most alternators sit around 14.4 and most batteries around 12.7 when fully charged.

This is not necessarily true, see my example below.

In the case of your test, from your alternator to your DMM. So even though you might be probing your battery terminals, you are really just taking a reading of your alternator's voltage. This is why when you turn the car off the voltage returns to battery voltage, mid-upper 12s.

Have you ever put a battery on a slow trickle charge? Chances are you haven't if you think the battery voltage never goes above 12.7V (I've put a dmm on my kinetik hc1800 after charging and sits at 13.81V). Sure, when it is NOT being charged by the alt (or in my case, a battery charger), it's going to drop to it's normal resting voltage (which mine does after a night of rest). The point I'm making is that the battery helps out before voltage drops to 12V, or even 12.7V. For this reason, the image is misleading...

 

[spoonraker 10+ year member]

Ryan, you just don't get it do you?

The diagram isn't an actual test, it's just a picture someone made to help illustrate the principal.

Regardless of what the specific voltages of your alternator/battery are, it doesn't make a difference. The point is, a cap doesn't prevent the load from jumping to your battery, it just delays it for an insignificant amount of time, end of story.

System voltage will remain basically constant throughout the circuit, barring any excessive resistance. A cap's voltage is and will be the same as system voltage, including the batt

Of course a capacitor's voltage will remain roughly the same as the rest of the system, that's what they are designed for : Rapid charge/discharge. This is the same reason why they do nothing in car audio, they discharge so quickly that they can't stabilize the voltage, only delay the inevitable drop down the battery level.

Seriously, why is this so hard to understand?

 

[audioholic 5,000+ posts]

Of course a capacitor's voltage will remain roughly the same as the rest of the system, that's what they are designed for : Rapid charge/discharge. This is the same reason why they do nothing in car audio, they discharge so quickly that they can't stabilize the voltage, only delay the inevitable drop down the battery level.

You are ignoring some pretty important details, like actual current draw, length of this peak demand, actual charging system capabilities... not to mention the amount of stored capacitance you are working with. This many assumptions rarely leads to a solid conclusion, and this is no exception.
A cap will filter out some 'current ripple' (call that what ever you like, it all means the same thing), but how much, how long, and how effective it will be is determined by more than whether or not its for "car audio". I really dont see that you've proven your statement at all. With that said, I do tend to agree their neccesity in car audio is over-sensationalized.

Seriously, why is this so hard to understand?

Why are you trying to over-simplify it?

 

[RAM_Designs 5,000+ posts]

Ryan, you just don't get it do you?
The diagram isn't an actual test, it's just a picture someone made to help illustrate the principal.

Then the principal they're describing isn't very accurate. Look at what it says at "T2". It says that that is when voltage drops to that of the battery...this is also shown to be exactly at 12V, which simply is NOT the case. People see the huge dip from 14V to 12V and think they have to have a cap. If the illustration was accurate and showed a very shallow drop in voltage, then maybe people would realize what the situation is really like.

Spoon, you simply don't get it, do you? //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[spoonraker 10+ year member]

Why are you nitpicking every detail of a purposefully simplified explanation?

Yes there are TONS of variables, but in the huge majority of cases, a capacitor, for the purpose of helping out a weak electrical system, will have no noticeable effect.

 

[audioholic 5,000+ posts]

Why are you nitpicking every detail of a purposefully simplified explanation?
Yes there are TONS of variables, but in the huge majority of cases, a capacitor, for the purpose of helping out a weak electrical system, will have no noticeable effect.

You really should quote the person you are talking to.
I 'nitpick' beause I dont like someone with the attitude of "why am I the only one here who understands" when he is not even totally correct.

 

[spoonraker 10+ year member]

I never said I'm the only one who understands, I said "why don't you understand"

Clearly you do understand, you for some reason can't just accept what is a generally true statement and you feel the need to tear it down by bringing up useless examples of times when it might not be completely true. Nobody said they are always useless, and nobody said they don't do anything at all. All that was said is that in the majority of cases the effect they have on the electrical system is very minimal. Period. Stop arguing, it's a true statement.

 

[RAM_Designs 5,000+ posts]

I never said I'm the only one who understands, I said "why don't you understand"
Clearly you do understand, you for some reason can't just accept what is a generally true statement and you feel the need to tear it down by bringing up useless examples of times when it might not be completely true. Nobody said they are always useless, and nobody said they don't do anything at all. All that was said is that in the majority of cases the effect they have on the electrical system is very minimal. Period. Stop arguing, it's a true statement.

I'm arguing about the graph used to illustrate voltage drops. I am then saying that it is a FACT that while the engine is running, battery voltage it much higher than what the graph states. I'm using this FACT as reason why upgrading your battery is more important than what the graph dictates, since the battery supplies power much sooner than the graphs says...

I don't care about how useful capacitors are, nor am I arguing about their importance in an audio system...once you realize that, try and post something to refute what I'm saying. Otherwise, stop trying to say that I'm arguing things in which I am not arguing about(usefullness of caps), you'll have a very hard time proving any of my statements wrong.

 

[audioholic 5,000+ posts]

I never said I'm the only one who understands, I said "why don't you understand"
Clearly you do understand, you for some reason can't just accept what is a generally true statement and you feel the need to tear it down by bringing up useless examples of times when it might not be completely true. Nobody said they are always useless, and nobody said they don't do anything at all. All that was said is that in the majority of cases the effect they have on the electrical system is very minimal. Period. Stop arguing, it's a true statement.

Perhaps I misunderstood you then when you said this...

This is the same reason why they do nothing in car audio...