Alternator question

[ejschultz 10+ year member]

Factoring in the stock electrical components isn't as important as you think it would be. Sure the headlights pull about 15 amps and the A/C can pull upwards of 30 amps. What do you think a stock 105 amp alternator does at idle? I'd assume it's close to 30 or 40 amps at idle. If you're driving at night and you have the A/C on, you'd be f*cked with a 105 amp alternator as soon as you come to a stoplight. I think a 140 amp alternator would definitely be an upgrade for you. It wouldn't be a huge upgrade, but it would suffice for the kind of power you're pulling right now and if you upgrade later on to 1500 watts, it's definitely going to be better than a stock alternator but you'll probably still have some voltage drops. I'm currently doing about 1300 watts RMS with my Caprice between my mono amp and my 4 channel. My mono amp is 80% efficient; I'm not sure how efficient my 4 channel is. I'm running a 140 amp alternator that benched at 98 amps at idle and 163 peak. At full tilt, I get a slight voltage drop, but nothing like I had before. I used to dip down into the mid 11s with my stock alternator (105 amp) and a big 3 with 1/0. Now, the lowest I've seen, at full tilt, was 12.8 volts at idle. My headlights don't dim anymore. I can definitely tell that the alternator made a difference.

 

[bubbagumper6 5,000+ posts]

Factoring in the stock electrical components isn't as important as you think it would be. Sure the headlights pull about 15 amps and the A/C can pull upwards of 30 amps. What do you think a stock 105 amp alternator does at idle? I'd assume it's close to 30 or 40 amps at idle. If you're driving at night and you have the A/C on, you'd be f*cked with a 105 amp alternator as soon as you come to a stoplight. I think a 140 amp alternator would definitely be an upgrade for you. It wouldn't be a huge upgrade, but it would suffice for the kind of power you're pulling right now and if you upgrade later on to 1500 watts, it's definitely going to be better than a stock alternator but you'll probably still have some voltage drops. I'm currently doing about 1300 watts RMS with my Caprice between my mono amp and my 4 channel. My mono amp is 80% efficient; I'm not sure how efficient my 4 channel is. I'm running a 140 amp alternator that benched at 98 amps at idle and 163 peak. At full tilt, I get a slight voltage drop, but nothing like I had before. I used to dip down into the mid 11s with my stock alternator (105 amp) and a big 3 with 1/0. Now, the lowest I've seen, at full tilt, was 12.8 volts at idle. My headlights don't dim anymore. I can definitely tell that the alternator made a difference.

You just contradicted yourself there...if your stock alt only produces 30-40A and your electrical components draw at least 45A, then you would already be seeing voltage drops when you stop at a red light...

Most of your advice is based on the assumption that a stock alt only puts out 30-40A at idle which I do not believe you are qualified to make.

 

[rosrock 10+ year member]

u c... what i dont think u guys can comprehend is that im not trying to get EVERY ounce of wattage i can ESPEICALLY at idle so dont worry about that.. dont even take that to concederation. I know its "best" to get a 200 amp alt say... however i have already said i am not looking to get the "best" or get out every millimeter of my system. Im simply saying that i can get a 160 amp alt(instead of what i have now which is 105 amp) for 100 dollars and it would make a big difference. Now im simply asking if this make make quite a difference... and AGAIN.. im not going top notch blah blah yes i know i could do better for 200 more bucks...(300 instead of 100 for 40 more amps).

(I know you guys are just trying to help but now u have to take into concid of what im typing.)

thx for help so far

 

[audioholic 5,000+ posts]

If you want a decent alt with decent power for an okay price check out powerbastards.com. 1500watts/12volts = 125amps of current draw at full tilt more or less.

If he was burping a sine wave, then yes. But playing music, the average current draw over time will be a fraction of that. Exactly what it will be is impossible for us to know.

No music sends a full signal with 100% duty cycle, (almost) nobody listens to their system 100% full blast 100% of the time, and we all listen to different music types which can greatly alter that avg current draw over time. Too many unknowable factors here to conclude what you do or dont need in terms of an alternator. You already have what you have, if it aint broke, dont fix it. When you upgrade your amplifier, if it breaks, fix it. If it doesn't break, dont fix it then either.

 

[bubbagumper6 5,000+ posts]

u c... what i dont think u guys can comprehend is that im not trying to get EVERY ounce of wattage i can ESPEICALLY at idle so dont worry about that.. dont even take that to concederation. I know its "best" to get a 200 amp alt say... however i have already said i am not looking to get the "best" or get out every millimeter of my system. Im simply saying that i can get a 160 amp alt(instead of what i have now which is 105 amp) for 100 dollars and it would make a big difference. Now im simply asking if this make make quite a difference... and AGAIN.. im not going top notch blah blah yes i know i could do better for 200 more bucks...(300 instead of 100 for 40 more amps).
(I know you guys are just trying to help but now u have to take into concid of what im typing.)

thx for help so far

The flaw in your logic is that if your trying to draw more current than what you have on hand, your going to get voltage drops...voltage drops WILL kill your amplifier, I've seen it happen...in person.

So if your really concerned about saving money and don't want to get the appropriate size alt, then when you get your new alt you need to back the gains down until your not getting significant voltage drops.

 

[bubbagumper6 5,000+ posts]

If he was burping a sine wave, then yes. But playing music, the average current draw over time will be a fraction of that. Exactly what it will be is impossible for us to know.
No music sends a full signal with 100% duty cycle, (almost) nobody listens to their system 100% full blast 100% of the time, and we all listen to different music types which can greatly alter that avg current draw over time. Too many unknowable factors here to conclude what you do or dont need in terms of an alternator. You already have what you have, if it aint broke, dont fix it. When you upgrade your amplifier, if it breaks, fix it. If it doesn't break, dont fix it then either.

While this is true, listening to any kind of rap can have the same effect as listening to a test tone. Some of those bass lines are just steady hits of a certain frequency which can push an amp to it's limit and draw peak current. You don't have to draw 100% current all the time for it to be a problem.

 

[ahole-ic]

If he was burping a sine wave, then yes. But playing music, the average current draw over time will be a fraction of that. Exactly what it will be is impossible for us to know.
No music sends a full signal with 100% duty cycle, (almost) nobody listens to their system 100% full blast 100% of the time, and we all listen to different music types which can greatly alter that avg current draw over time. Too many unknowable factors here to conclude what you do or dont need in terms of an alternator. You already have what you have, if it aint broke, dont fix it. When you upgrade your amplifier, if it breaks, fix it. If it doesn't break, dont fix it then either.

It's not that what you're saying isn't true, it's just that there really isn't a whole lot of gray area. When we talk about upgrading the charging system, we're not talking about the duty cycle or average current draw over a period of time. We're talking about preparing for the maximum draw. Sure in ANY scenario the maximum current draw will only happen for a minimal time. That is what you upgrade for though. I have an amp that will put out 6000 watts. It probably averages about 800 IF that. Should I not have upgraded my charging system based on the duty cycle? My intended purpose was to get the maximum potential out of my amp. When the voltage drops into the 12's my amp doesn't do the power I want. Of course I have to then power for the heaviest draws... not duty cycle.

He came here asking what it would take to power his 1500watt amp. He wasn't asking what it would take to turn it on. He was asking what it would take to get the full 1500 watts from it. If he goes with a cheap little alt that says it'll do a few more amps than stock, is that going to keep his voltage up at 14.4 where his amp actually puts out rated power? Probably not.

While I see your point, I do not think it was relevant to the discussion. We are simply answering the question as it was asked.

 

[audioholic 5,000+ posts]

While this is true, listening to any kind of rap can have the same effect as listening to a test tone. Some of those bass lines are just steady hits of a certain frequency which can push an amp to it's limit and draw peak current. You don't have to draw 100% current all the time for it to be a problem.

You are confused. A sine wave is a 100% duty cycle signal. No rap song has a single note played at 100% recording volume, 100% of the song.

 

[rosrock 10+ year member]

i understand what ur saying ecrack

 

[audioholic 5,000+ posts]

It's not that what you're saying isn't true, it's just that there really isn't a whole lot of gray area. When we talk about upgrading the charging system, we're not talking about the duty cycle or average current draw over a period of time. We're talking about preparing for the maximum draw. Sure in ANY scenario the maximum current draw will only happen for a minimal time. That is what you upgrade for though. I have an amp that will put out 6000 watts. It probably averages about 800 IF that. Should I not have upgraded my charging system based on the duty cycle? My intended purpose was to get the maximum potential out of my amp. When the voltage drops into the 12's my amp doesn't do the power I want. Of course I have to then power for the heaviest draws... not duty cycle.He came here asking what it would take to power his 1500watt amp. He wasn't asking what it would take to turn it on. He was asking what it would take to get the full 1500 watts from it. If he goes with a cheap little alt that says it'll do a few more amps than stock, is that going to keep his voltage up at 14.4 where his amp actually puts out rated power? Probably not.

While I see your point, I do not think it was relevant to the discussion. We are simply answering the question as it was asked.

If the OP was an SPL competitor looking to keep peak output through a 30 second burp, Id agree with you. But this will be a daily system, playing music (I assume?). Transient signal strength, therefore transient amplifier draw.

Ive run a 1000-1200 watt system on a 90amp alt before. Ideal? Obviously not. Did it work? Yep. It had some dimming, but it didnt cut out at high volume, and the amplifiers certainly didnt die. If your alt is close enough to keep up over time, and your batt capacity is sufficient to keep your voltage from dropping to dangerous levels during peak demand, you'll likely be fine.

This is funny to me, because Im usually the guy on the other end of this debate. But I only break out the math when its a clear cut case of insufficient alternator capacity. 2500 watts and a 100amp alt, yeah its going to be problems. But the situation is not nearly so clear cut as "1500watts/12volts = 125amps of current draw at full tilt" like someone said earlier. Your 1500 watt amp will likely only draw that 125 amps for fractions of a second, so building a charging system that will handle that 100% of the time is over kill. I actually prefer to build my charging systems exactly that way, over built. But that doesn't mean Id recommend it to a relative noob just wanting to know if his alt will cut it. It may, it may not. If he keeps an eye on his voltage, he'll know without just guessing and plunking down the cash on an assumption of a problem.

 

[ahole-ic]

If the OP was an SPL competitor looking to keep peak output through a 30 second burp, Id agree with you. But this will be a daily system, playing music (I assume?). Transient signal strength, therefore transient amplifier draw.
Ive run a 1000-1200 watt system on a 90amp alt before. Ideal? Obviously not. Did it work? Yep. It had some dimming, but it didnt cut out at high volume, and the amplifiers certainly didnt die. If your alt is close enough to keep up over time, and your batt capacity is sufficient to keep your voltage from dropping to dangerous levels during peak demand, you'll likely be fine.

This is funny to me, because Im usually the guy on the other end of this debate. But I only break out the math when its a clear cut case of insufficient alternator capacity. 2500 watts and a 100amp alt, yeah its going to be problems. But the situation is not nearly so clear cut as "1500watts/12volts = 125amps of current draw at full tilt" like someone said earlier. Your 1500 watt amp will likely only draw that 125 amps for fractions of a second, so building a charging system that will handle that 100% of the time is over kill. I actually prefer to build my charging systems exactly that way, over built. But that doesn't mean Id recommend it to a relative noob just wanting to know if his alt will cut it. It may, it may not. If he keeps an eye on his voltage, he'll know without just guessing and plunking down the cash on an assumption of a problem.

You're missing the point. He wants to put out 1500 watts. When the voltage drops, is his amp going to put out those 1500 watts? Probably not. Answer the question as it was asked. If he wants to be able to put that power out, he has to have a sufficient charging system. He didnt' ask if the amp will stay powered. He asked if he could put out 1500 watts. Please try to stay on subject.

 

[rosrock 10+ year member]

ok guys, maybe i can clear this up... i will be listening to music... not burping or anything trying to get the highest db possible or anything.. not trying to get EVERY ounce of my system. HOWEVER, i normally prolly run u know maybe.. 700-900 rms? i dont like to hurt my ears normally as i know i will regret it in the future. What im looking for is for every ONCE IN A WHILE or a song or two, when i get in the ZONE //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif. I want to be able to crank it and be able to 1400-1500 rms out of the amp.. but even then i prolly wont really be getting that because again ill repeat i never BURP .. i just listen to hip hop music. In this type of instance, would a 160 amp alt off ebay do the job for me?

 

[ahole-ic]

ok guys, maybe i can clear this up... i will be listening to music... not burping or anything trying to get the highest db possible or anything.. not trying to get EVERY ounce of my system. HOWEVER, i normally prolly run u know maybe.. 700-900 rms? i dont like to hurt my ears normally as i know i will regret it in the future. What im looking for is for every ONCE IN A WHILE to be able to crank it and be able to get the full 1400-1500 rms out of the amp.. but even then i prolly wont really be getting that because again ill repeat i never BURP .. i just listen to hip hop music. In this type o instance, would a 160 amp alt do the job or me?

It would come close enough. You're right though, things like impedence rise etc will keep you from seeing that power at resonance, but if you're not going to compete it doens't matter. If you're able to get a CLEAN 1000 watts, that's probably as much as anyone really wants for music anyways. I'll be honest also. The difference going from a true 1000 watts to a true 1500 watts is VERY minimal at best.

 

[rosrock 10+ year member]

why do u say that?? 1000 rms vs 1500 seems like a big difference!? I run a custom hybrid tc9 12" in a 2.5 @ 33 (got it off ebay 1500 rms rated) with my diercted 1500d that does either 1200 at 1 or 1100 at 1 ohm, it has 3 30 amp fuses...(on the site it says 1200 but in the manual it says 1100).. and i plan on upgrading to a 1500 rms amp. Wouldnt there be a very noticeable difference?(of course assuming i did get a 160 amp alt)

by the way thanks for ur guyses input! very good info to know.. what all of u are adding in

 

[audioholic 5,000+ posts]

Please try to stay on subject.

If my replies make you feel threatened, you have no reason to fear me.

Probably not.

My point exactly, you dont know. So until there's a problem, dont tell him to spend the money.