voltage questions

[taintedplay 10+ year member]

ok so im probabbly getting a big batt soon, and i have a few questions. first, im guessing theres voltage meter's i could put on my dash, where on the runs would i put em?

also, i hear about voltages, whats a high voltage and a low one, and kinda the basics about that

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[audiolife 5,000+ posts]

A safe window of voltage to stay in is 14.9v to 11.7v. If your system stays in the 13 volt range solid it is pretty good.

 

[thegreatestpenn 5,000+ posts]

dropping below 14.4V means you're pulling more amps than your Alt can handle. dropping below 12.5V means you're pulling more amps than your batt can handle

 

[SPL Blazer 10+ year member]

dropping below 14.4V means you're pulling more amps than your Alt can handle.

Huh?

Since it's cold out my battery always starts out at 15.0-15.3 volts, but when I start driving for a bit the voltage never stays at 14.4 volts or higher. I have a very good electrical system and my normal voltage range with music playing at low volumes is 13.9-14.2.

14.4 volts is a great place to start out, and it's where all car audio piece's are tested at, but just because your voltage drops below 14.4 volts doesn't mean your exceeding your alternators capability.

 

[old_dude 10+ year member]

Hey there! I'm new to this forum, and this is my first post/reply. I'm no expert by any means, but I do have a bit of knowledge based on asking questions, reading, and mostly experience. I've experienced all the "not enough voltage/too much draw" from my battery stuff in the past, even frying wires right off the alternator! So this time, on my current setup, I decided that since CURRENT DRAW is more important than VOLTAGE (to me, anyway) I wanted to know exactly how much draw my sh*t was pulling from my battery. So I invested $163+ (list at $260) for an AutoMeter Cobalt Amp Current Gauge, meaning "amps" in 3 ways to me: it measures AMPS being drawn from AMPS and will be (when I'm finally done) hooked to my AMPS. I chose this route for several reasons. Being a former auto mechanic, I've had bosses and coworkers always tell me to buy a Ammeter to monitor current draw rather than a Volt Meter to worry about voltage draw when it comes to car audio. Made sense to me! It's the amperage current draw that is basically making headlights flash and stuff from the beat of your thumpage. Oh, don't get me wrong, we all want to make sure we keep our battery voltage at around 12-14 volts to make our systems perform to their peek expectations. But myself, I worry more about how much current is being ****** from my electrical system.

SO... (I'm getting to my point, sorry)//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

I would recommend to anyone who can afford one to get the gauge I got. As mentioned above, they are NOT cheap by any means. But this investment, not only being cool to look at, can help keep you from drawing too much current from your vehicle's electrical system. It has several modes of display, but the coolest and most effective is where it monitors current draw and displays it 10 times a second, which is best in my opinion. Very simple logic and install, too! You simply run your main power cable (0g, 1g, or whatever you choose) through a little "current transducer" that mounts with 2 screws. The transducer "picks up" the amount of current being drawn through it and displays it on the gauge. Cool and functional at the same time!

Check it out. This is where I got mine:

http://www.fixthisride.com/showproductdetail.jsp?prod_id=759&mid=A48&pid=6390

I think this is going to be a VERY wise investment I made. Just think I'll install it in the amp rack instead of in or under my dash.

 

[SPL Blazer 10+ year member]

I looked into those meters when I built my first real system in my Blazer, but the cost was way too much for what it does. They are cool, but seeing my voltage means more to me than how much amperage I'm drawing. Amperage draw shouldn't be all that hard to figure out. Go total up your fuse ratings on such things as wipers, heater and A/C, radio, headlights etc. Then total the amp ratings for all the fuses on your amps and you can get a general idea of your current amperage draw. Of course you have to keep in mind that if your sub amp is a 1500 watt amp and has a 150 amp fuse that your only going to come close to that amperage draw when your voltage is at 14.4 volts and the system is being played at full tilt, which isn't a normal volume for most of us to be playing at while just driving around. Seeing your amperage draw is a bonus for competitors, but we just use a clamp meter for that. Most guys just want to know their voltage isn't dropping too low, not that you'd be able to hear the difference between 14.4 volts and 13.9 volts at your amps.

 

[loopkiller 10+ year member]

In reality, the maximum amperage your car can provide is easy to calculate. The ability of your car to provide that current in a quick enough method to power your audio is the real dilemma. You can monitor the ability to provide current by simply monitoring your voltage. As amperage draw increases past current capacity, your voltage will sag. These dips in voltage can be seen visibly in your lights if the change is fast enough. Those same dips in voltage are what can kill your precious audio equipment.

 

[old_dude 10+ year member]

And you're both right. However, car audio doesn't really draw voltage as much as amperage from a technical and scientific standpoint.

To get all technical here:

We all know that AC is the current which supplies the audio signal path.

And we all know that DC is the current which supplies power to each component.

1 volt will move 1 amp through 1 ohm of resistance, at a rate of 1 watt. (Since amperage is current flow per second, and therefore, a watt is rated in seconds.)

To find the current draw of an amp, you just divide the RMS total by the battery's idle voltage. For example, in a system with 250 watts RMS (125wpc rms into 4 ohms) and and electrical system with 12.6VDC, the equation would come out to 250 devided by 12.6 for a current draw of 19.84 amps.

So, even though all this sounds like a bunch of mumble jumble to most of us, it is important to know, especially when deciding on how big of power cables to run.

As for a 1500 watt amp having a 150 amp fuse, I find that hard to understand. In fact, my present 1800 watt amp only has a pair of 30 amp fuses in it.

Sorry if I sound like an idiot. And I'm certainly not here to slam anyone's opinion or expertise. Nor make enemies. My only point is that to ME (everyone else can have their priorities), amperage draw is more vital than voltage draw.

Either way, I wish the OP, taintedplay, the best of luck in getting the most out of his system.

And as for the AutoMeter gauge, I think it was more of a "cool factor" when I got it, and the fact that I had a bunch of money to waste. Which is the likely reason it won't be mounted near the dash to stare at all day, but rather in the amp rack so when I'm back their tweeking things I can judge a few things.

 

[SPL Blazer 10+ year member]

As for a 1500 watt amp having a 150 amp fuse, I find that hard to understand. In fact, my present 1800 watt amp only has a pair of 30 amp fuses in it.

Thats pretty common with the lower quality amps. My RF 1501bd recommends a 150 amp fuse and was tested at 1650 watts @ 14.4 volts. But some lower class amps that claim to be a 1000 or 1500 watt amp might have fuses like yours, in which case they really don't put out the power the manufacturer claims. Amps like that will brag about being a 1500 watt amp, and the ratings will say 1000 watts @ 1 ohm, 1500 watts peak, but come with an 80 amp fuse. That 1500 watts peak is pretty much a bogus number used to help sell the amp. General guidelines would be 100 watts for every 10 amps, this is true with every quality amp I've seen to date. My HK4000D amp is rated at 4000 watts and recommends a 400 amp fuse, for those that actually use a fuse for those amps, hence 4000 watts/400 amps of current draw. Of course being that this amp isn't very efficient it doesn't really push out 4,000 watts like it says so it wouldn't draw 400 amps, but you get the idea.

 

[loopkiller 10+ year member]

And you're both right. However, car audio doesn't really draw voltage as much as amperage from a technical and scientific standpoint.
To get all technical here:

We all know that AC is the current which supplies the audio signal path.

And we all know that DC is the current which supplies power to each component.

1 volt will move 1 amp through 1 ohm of resistance, at a rate of 1 watt. (Since amperage is current flow per second, and therefore, a watt is rated in seconds.)

To find the current draw of an amp, you just divide the RMS total by the battery's idle voltage. For example, in a system with 250 watts RMS (125wpc rms into 4 ohms) and and electrical system with 12.6VDC, the equation would come out to 250 devided by 12.6 for a current draw of 19.84 amps.

So, even though all this sounds like a bunch of mumble jumble to most of us, it is important to know, especially when deciding on how big of power cables to run.

As for a 1500 watt amp having a 150 amp fuse, I find that hard to understand. In fact, my present 1800 watt amp only has a pair of 30 amp fuses in it.

Sorry if I sound like an idiot. And I'm certainly not here to slam anyone's opinion or expertise. Nor make enemies. My only point is that to ME (everyone else can have their priorities), amperage draw is more vital than voltage draw.

Either way, I wish the OP, taintedplay, the best of luck in getting the most out of his system.

And as for the AutoMeter gauge, I think it was more of a "cool factor" when I got it, and the fact that I had a bunch of money to waste. Which is the likely reason it won't be mounted near the dash to stare at all day, but rather in the amp rack so when I'm back their tweeking things I can judge a few things.

Bottom line is that BOTH voltage and amperage are important to DC electric components. If you are lacking in either, you have to make up with the other. So in the basic equation of P=I*V and you know you have an amp rated to 1000W RMS and your voltage is 14.4v, to solve for I your equation is:

I=1000W / 14.4v

If your voltage is 12.6v, then solving for I is:

I=1000W / 12.6v

You can see that your amperage will vary based on voltage. Knowing only one of the two is somewhat meaningless. Only with both figures can you see your true output. However, if you are going to measure only one, then voltage is far easier and less expensive to monitor than amperage. Since your voltage sags when you exceed current capacity, it is a very useful indicator of overall system stability.

 

[old_dude 10+ year member]

I agree (mostly), spl. Like the importance of large fuses. And amp manufacturers claiming higher ratings just to sell their product. But I don't really agree that Kenwood puts out low-quality products. I've owned several Rockford Fosgate (Punch & Power) amps, as well as Soundstream amps. And I realize that those 2 are great at actually advertising the REAL output of their amps. Still, 400 and 500 amp fuses? Where on this planet do you find those? I've never seen any above 150 amps. (Though I only went with 100 amp in my main power cable's fuse holder).

I'm still not exactly a fuse expert, nor do I claim to be. In fact, I called a major online retailer's technical people to ask this question (which proves I'm not up to par with fuse ratings!): "If my amplifiers have 30 and 40 amp fuses, plus the crossover back there, what amp fuse rating should I use in the inline holder?", to which they said a 100 amp would work fine.

You don't agree? My point wasn't that anyone's amps are better or worse according to the brand. My only point was that I am going by what I was told. And I would really appreciate YOUR opinion too. Seriously. I joined this forum to LEARN rather than INFORM, and therefore value other people's opinions and technical advice. As long as they don't call my brand choice junk. Kenwood has been around 10 times longer than RF, but I'm not slamming RF in any way, nor will I slam anyone else's choice of brands.

I would really appreciate finding a source where I can purchase higher rated fuses than 150 amps. I have BOTH holders, both AGU and ANL but I'm not sure exactly which one I should use. Any suggestions? The AGU's are much easier to replace, and they look nicer. But is one better than the other? I've done countless hours of searching tons of car audio and electronics sites but haven't really decided which fuse type is best, or where to get anything above 150 amps.

StreetWires makes Mini Wafer Fuses of 150 amps, but their AGU's I could only find up to 80 amps.

So, since it seems you are more knowledgeable on fuses than I am, I'll admit, can you tell me your opinion on if you think the 100's I already have will be enough (with my "lower quality amps with the bogus power ratings") for my 3 amps and 1 crossover? My plan is to run ONE main fuse inline with the main power cable, then seperate fuses in the fuse block to my devices. But wouldn't this be "fuse overkill" since the devices already have their own fuses?

Geez, now you have me afraid to even mention WHY I am running THREE distribution blocks! But EVERY local car audio store and installer I've mentioned it to around town all have said "That's a pretty cool idea, I never thought of that!", so I'm sort of proud of my ingenious idea.

 

[terra 5,000+ posts]

I agree (mostly), spl. Like the importance of large fuses. And amp manufacturers claiming higher ratings just to sell their product. But I don't really agree that Kenwood puts out low-quality products. I've owned several Rockford Fosgate (Punch & Power) amps, as well as Soundstream amps. And I realize that those 2 are great at actually advertising the REAL output of their amps. Still, 400 and 500 amp fuses? Where on this planet do you find those? I've never seen any above 150 amps. (Though I only went with 100 amp in my main power cable's fuse holder).
I'm still not exactly a fuse expert, nor do I claim to be. In fact, I called a major online retailer's technical people to ask this question (which proves I'm not up to par with fuse ratings!): "If my amplifiers have 30 and 40 amp fuses, plus the crossover back there, what amp fuse rating should I use in the inline holder?", to which they said a 100 amp would work fine.

You don't agree? My point wasn't that anyone's amps are better or worse according to the brand. My only point was that I am going by what I was told. And I would really appreciate YOUR opinion too. Seriously. I joined this forum to LEARN rather than INFORM, and therefore value other people's opinions and technical advice. As long as they don't call my brand choice junk. Kenwood has been around 10 times longer than RF, but I'm not slamming RF in any way, nor will I slam anyone else's choice of brands.

I would really appreciate finding a source where I can purchase higher rated fuses than 150 amps. I have BOTH holders, both AGU and ANL but I'm not sure exactly which one I should use. Any suggestions? The AGU's are much easier to replace, and they look nicer. But is one better than the other? I've done countless hours of searching tons of car audio and electronics sites but haven't really decided which fuse type is best, or where to get anything above 150 amps.

StreetWires makes Mini Wafer Fuses of 150 amps, but their AGU's I could only find up to 80 amps.

So, since it seems you are more knowledgeable on fuses than I am, I'll admit, can you tell me your opinion on if you think the 100's I already have will be enough (with my "lower quality amps with the bogus power ratings") for my 3 amps and 1 crossover? My plan is to run ONE main fuse inline with the main power cable, then seperate fuses in the fuse block to my devices. But wouldn't this be "fuse overkill" since the devices already have their own fuses?

Geez, now you have me afraid to even mention WHY I am running THREE distribution blocks! But EVERY local car audio store and installer I've mentioned it to around town all have said "That's a pretty cool idea, I never thought of that!", so I'm sort of proud of my ingenious idea.

Never seen an inline 300+ amp fuse?

 

[old_dude 10+ year member]

4000 watt mono amp? Dude, I'm jealous! And apparently have reason to be embarrassed about my cheezy K-Woo's. I'm not a competitor, just a measly little guy who wants decent sound for his shopping dollar. Hell, I'm the first to admit that Kenwood can in no way compare to some of those top brands of high-end amps, but for the average "Joe Consumer" like me, they sure beat buying an even cheaper brand of amps that advertise even higher outputs than mine do (like those swap meet specials do so often! "2000 watts RMS! Today's special, only $39.95!")

You guys with those high-dollar amps and sound-off quality systems are my heroes, but I doubt I'll ever be that high-end just for driving around town listening to some decent tunage.

A lowly Kenwood owner:crap:

 

[loopkiller 10+ year member]

They make up to 750A ANL fuses. Those are the largest I have found via Google. There might be larger that Google does not know about yet //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[SPL Blazer 10+ year member]

I have yet to see any high quality Kenwood amps, I used to run some mono ones years ago, and love their headunits, so I'm not gonna bash Kenwood at all. The Old School RF Punch and Power series amps were awesome, now they're all pretty much the same over rated junk. The newer RF power series amps come with a 500 amp fuse, I didn't believe it til I saw one at a show last season. Stinger and other companies sell ANL fuses with ratings up to 350 amps, I've heard of 400 amp fuses but have never seen one. I only use my 4000 watt amp for competitions so I don't waste money on fuses for that one.

As far as the 100 amp fuse in your system, I'd say your fine with it. The fuses before or at your amp should be what your amp recommends, but the fuse on your main line can be as high as what your wire needs. The purpose of a fuse near your battery is designed to protect your power wire, not your equipment. So for that wire you can use a fuse rated for more than the total of your equipments fuses, but not for more than your wire is rated to handle.