# 12.5 volts vs 14.4 volts



## dsw1204 (Mar 23, 2015)

This is something I've guessed at, but don't really know. So, I thought I'd find out from you fine people at diymamobileaudio. 

I was looking at specs of a JL amp and there were two sets of specs. One with 12.5 volts and the other with 14.4 volts. What is the difference? I mean, is 12.5 volts where the car is just idling (or even turned off)? Is 14.4 volts where the car is actually driving down the road?

That is what I was guessing, but I just don't really know for sure.


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## nineball76 (Mar 13, 2010)

Typically 14+ is with the car running, 12.6-8 is car off, battery powered.


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## Truthunter (Jun 15, 2015)

It also means that the amp does not have a regulated power supply. If it did, the power output capability would not change with input voltage fluctuations.


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## dsw1204 (Mar 23, 2015)

nineball76 said:


> Typically 14+ is with the car running, 12.6-8 is car off, battery powered.


Okay, when the car is turned on and idling, the battery is outputting 14.4 volts. When the car is driving down the road at 20,30, or 65 mph, it's also churning out 14.4 volts. It's only churning 12.5 volts when turned off, correct?

Well, I got two of the three scenarios correct.

Thanks.


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## dsw1204 (Mar 23, 2015)

Truthunter said:


> It also means that the amp does not have a regulated power supply. If it did, the power output capability would not change with input voltage fluctuations.


I've heard of those terms before and that's another thing I did not understand. What exactly is the difference between regulated and unregulated amplifier?

Other than a constant output with the different voltages (and I am not sure if that is a benefit or not), are there any other differences between being regulated and unregulated?


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## Frogsrule (Aug 25, 2016)

14.4V is the nominal voltage referenced in many SAE documents and standards. That's where it came from. Typical charge voltage is 13.2-13.8.


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## gijoe (Mar 25, 2008)

dsw1204 said:


> Okay, when the car is turned on and idling, the battery is outputting 14.4 volts. When the car is driving down the road at 20,30, or 65 mph, it's also churning out 14.4 volts. It's only churning 12.5 volts when turned off, correct?
> 
> Well, I got two of the three scenarios correct.
> 
> Thanks.


No, this isn't really correct. Your voltage will fluctuate while you're driving. It isn't 12.5 while the car is off, and 14.4 while it's running, it should be somewhere within that range though. Turn on the AC, the voltage will drop, roll the windows up or down, the voltage will drop, it's not uncommon for the voltage to stay in the mid to high 13's. It's not a big deal anyway since the output from the amp isn't going to change much at all, the difference will be negligible, so don't try too hard to estimate your output potential at a given voltage.


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## nineball76 (Mar 13, 2010)

gijoe said:


> No, this isn't really correct. Your voltage will fluctuate while you're driving. It isn't 12.5 while the car is off, and 14.4 while it's running, it should be somewhere within that range though. Turn on the AC, the voltage will drop, roll the windows up or down, the voltage will drop, it's not uncommon for the voltage to stay in the mid to high 13's. It's not a big deal anyway since the output from the amp isn't going to change much at all, the difference will be negligible, so don't try too hard to estimate your output potential at a given voltage.


This isn't 100% true either. Dependant on the vehicle and is electrical. My Ram with a 270a pcm controlled alt, zero fluctuation. When running is 14.1 at all times. Idle or highway, 14.1.


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## gijoe (Mar 25, 2008)

nineball76 said:


> This isn't 100% true either. Dependant on the vehicle and is electrical. My Ram with a 270a pcm controlled alt, zero fluctuation. When running is 14.1 at all times. Idle or highway, 14.1.


It's not going to stay exactly at 14.1 volts regardless. It will fluctuate some when you turn on an accessory. I have no doubt that it does a great job staying at 14.1 volts, but there will be some fluctuation, even if it's minor. My point was that regardless of the fluctuations, the change in output will be negligible. So whether the voltage is 14.1 volts at all times, or if it goes from 12.9 to 14.2 volts the impact on the stereo system is negligible.


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## Frogsrule (Aug 25, 2016)

The output of the amp doesn't change unless you're at max power. That difference in voltage affects the most power the amp CAN make, not the power the amp makes.


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## Victor_inox (Apr 27, 2012)

Truthunter said:


> It also means that the amp does not have a regulated power supply. If it did, the power output capability would not change with input voltage fluctuations.


That explains it pretty clearly.


dsw1204 said:


> I've heard of those terms before and that's another thing I did not understand. What exactly is the difference between regulated and unregulated amplifier?
> 
> Other than a constant output with the different voltages (and I am not sure if that is a benefit or not), are there any other differences between being regulated and unregulated?


No.


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## Alrojoca (Oct 5, 2012)

gijoe said:


> No, this isn't really correct. Your voltage will fluctuate while you're driving. It isn't 12.5 while the car is off, and 14.4 while it's running, it should be somewhere within that range though. Turn on the AC, the voltage will drop, roll the windows up or down, the voltage will drop, it's not uncommon for the voltage to stay in the mid to high 13's. It's not a big deal anyway since the output from the amp isn't going to change much at all, the difference will be negligible, so don't try too hard to estimate your output potential at a given voltage.


It is actually the opposite with many modern cars these days, if the air blower, lights, or any constant electrical device is off, some can remain at 12.6 volts 95% of the time while driving, once the air blower is on, it can be a 60 % of the time at 12.6 volts and sometimes peaking at 14.2-3 volts for not too long periods of time, to keep the battery charged, like a smart charging battery charger. Another thing I noticed some manufacturers or some models, limit that fluctuation at a certain speed, once you drive above 55 mph for example, the voltage will remain at 14 plus volts.

My guess they want the cars to save gas at lower speeds or city driving.


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## Alrojoca (Oct 5, 2012)

On another note, some of the amplifiers power at 12 or 14 volts differences is hardly noticeable maybe more measured than anything else, and with music, 10-20 watts is meaningless in actual music listening


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## oabeieo (Feb 22, 2015)

The HD amps have three modes based on voltage 
They are fully regulated power supplies however it has two stages and a third stage

The first stage is normal operation the second stage is lowered output because of low voltage the third stage is protect because it drops below 9 V


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## dsw1204 (Mar 23, 2015)

The reason I posted this thread was that when I was viewing the specs of the JL amp (I forget the model #), I saw that the posted power was 55% greater at 14.1 volts compared to 12.5 volts. That, to me, seems to be a pretty big difference. Is that typical?


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## gijoe (Mar 25, 2008)

dsw1204 said:


> The reason I posted this thread was that when I was viewing the specs of the JL amp (I forget the model #), I saw that the posted power was 55% greater at 14.1 volts compared to 12.5 volts. That, to me, seems to be a pretty big difference. Is that typical?


It takes double (or half) the power to increase (or decrease) by just 3dB. Don't get too caught up on power.


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## oabeieo (Feb 22, 2015)

dsw1204 said:


> The reason I posted this thread was that when I was viewing the specs of the JL amp (I forget the model #), I saw that the posted power was 55% greater at 14.1 volts compared to 12.5 volts. That, to me, seems to be a pretty big difference. Is that typical?



On the HD amp yes . They gulp power of its available . 

The xd amps are more equal as far as power goes but not as nice 

I'm pretty sure they did that to idiot proof the guy that puts 2500 W on his stock alternator in a single battery using HD amps. 

If you give them the power they need they can do some pretty amazing things


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## mrnix (Mar 2, 2009)

My apologies if someone stated this already, but I wanted to clarify for the OP's question. The battery puts out approximately 12.5 volts, while the alternator - whose job is to provide electrical power while the car is running, as well as charge the battery - puts out low 13s to mid 14 volts. Greater voltage than 12.5 being necessary to charge the battery while the engine is running.

I'm sure it's rudimentary to some, but I understand how it could be confusing if you are new to car audio or 12 volt electrical systems.


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## dsw1204 (Mar 23, 2015)

gijoe said:


> It takes double (or half) the power to increase (or decrease) by just 3dB. Don't get too caught up on power.


That I did know. I just didn't realize how much difference that voltage made. And, I am not usually caught up in the difference in RMS wattage. But, having that extra wattage does give you some additional headroom and that I do like.


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## diy.phil (May 23, 2011)

@dsw1204 please buy a Stinger SGP12 to look at the voltage while driving or when turning on/off some items like A/C, heater or headlights. Some modern vehicle(s) only recharge its battery (around 13.8 to 14.5V) when it's needed and at other times idle at 12.5V to 12.8V when it's not necessary to recharge it. After looking at it for a while on a new 2016/2017 vehicle with the AGM battery as an example... it's like almost like no rhyme or reason but purely when the electronics think it's time to recharge it. Some vehicles with auto stop/start will restart the motor when it has been idling too long at a stop light or a similar situation. The vehicles from a few years back sometimes may bump up the voltage when we have some items on. The older vehicles with wet/acid battery definitely will bump it up when we turn on some items. It's the new ones that does whatever it wants to do according to some situations or sensors.


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## oabeieo (Feb 22, 2015)

Diy Phil is right. 
If it's in a Honda you'll need to do a ELD work around .


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## nineball76 (Mar 13, 2010)

mrnix said:


> My apologies if someone stated this already, but I wanted to clarify for the OP's question. The battery puts out approximately 12.5 volts, while the alternator - whose job is to provide electrical power while the car is running, as well as charge the battery - puts out low 13s to mid 14 volts. Greater voltage than 12.5 being necessary to charge the battery while the engine is running.
> 
> I'm sure it's rudimentary to some, but I understand how it could be confusing if you are new to car audio or 12 volt electrical systems.


To be technical, batteries don't put out any voltage. They're a storage device, and can only hold up to xxx volts. While the alternators job is to change and maintain the storage device (battery) at the same time providing enough extra current to apply the demands of everything else the car uses to operate. 

Alternator = power source 
Battery = storage device that does not make energy.


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> To be technical, batteries don't put out any voltage. They're a storage device, and can only hold up to xxx volts. While the alternators job is to change and maintain the storage device (battery) at the same time providing enough extra current to apply the demands of everything else the car uses to operate.
> 
> Alternator = power source
> Battery = storage device that does not make energy.


Sorry brother your statement is ********. 
Alternator keep battery charged but amplifiers draw from battery. If your alternator capable of keeping up with that job you'll have balanced electrical system. 

Sent from my SAMSUNG-SM-G925A using Tapatalk


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## nineball76 (Mar 13, 2010)

I disagree. Amps draw from alt excess first, until you exceed capacity. Then batteries make up the remaining amperage needed.


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> I disagree. Amps draw from alt excess first, until you exceed capacity. Then batteries make up the remaining amperage needed.


You can disagree all you want. 70amp alternator (most common these days) job is to keep battery charged while amps burst draw of 100-150A on demand. Since it`s all at the same circuit wording doesn`t matter. disconnect battery while drawing 100 Amp and your car will starve for current and die. Disconnect alternator and it will work for hours until battery is empty.


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## nineball76 (Mar 13, 2010)

Victor_inox said:


> You can disagree all you want. 70amp alternator (most common these days) job is to keep battery charged while amps burst draw of 100-150A on demand. Since it`s all at the same circuit wording doesn`t matter. disconnect battery while drawing 100 Amp and your car will starve for current and die. Disconnect alternator and it will work for hours until battery is empty.


That's a competely off comment reply. When the topic was 12v vs 14v and my replies were about alternator levels and charging higher than stock levels. Example: 270a alt, dual batteries, 2000 watts and vehicle uses 75a. Amps aren't drawing from the batteries, they're getting their power from the alt first.


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## nineball76 (Mar 13, 2010)

270a or 25a alt doesn't matter, the amps are drawing off the top voltage first, and batteries are never a 14v source! So therefore the the amps are drawing the first ampacity off the alt, then they get the remainder from the batteries (the storage).


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> That's a competely off comment reply. When the topic was 12v vs 14v and my replies were about alternator levels and charging higher than stock levels. Example: 270a alt, dual batteries, 2000 watts and vehicle uses 75a. Amps aren't drawing from the batteries, they're being their power from the alt first.


 It`s the same circuit, not separated unless yo use double batteries with isolator. But in that case you`ll be drawing from dedicated battery and not alternator at all. It`s maybe off comment but just to set record straight.


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> 270a or 25a alt doesn't matter, the amps are drawing off the top voltage first, and batteries are never a 14v source! So therefore the the amps are drawing the first ampacity off the alt, then they get the remainder from the batteries (the storage).


Exactly doesn`t matter because current drawn from battery.
Excess voltage from alternator needed to keep that battery charged. they all on the same circuit, remember?


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## nineball76 (Mar 13, 2010)

No its not, where do you think the excess is going? not into a 12.8 storage device. Batteries are never anything more than overflow


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## Victor_inox (Apr 27, 2012)

You stubborn one ,aren`t ya? OK here is pseudo scientific test for you, go disconnect alternator and tell me if you can hear any difference at full blast. then connect it back and disconnect battery, ohhhh wait don`t do it it might kill your alternator.


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## nineball76 (Mar 13, 2010)

Victor_inox said:


> You stubborn one ,aren`t ya? OK here is pseudo scientific test for you, go disconnect alternator and tell me if you can hear any difference at full blast. then connect it back and disconnect battery, ohhhh wait don`t do it it might kill your alternator.


Ok do the same test backwards. Disconnect your battery and see. 150a system on my 270a alt doesn't even need the batteries for anything more than starting power.


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## nineball76 (Mar 13, 2010)

Batteries are nothing more than reserve for when you exceed your energy suppliers abilities


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> Ok do the same test backwards. Disconnect your battery and see. 150a system on my 270a alt doesn't even need the batteries for anything more than starting power.


 Maybe but it`s all the same circuit, fact you not understanding.
In case of your 150A alternator what going to happen if you draw 250A, without battery? You can ditch that battery and use bank of supercapasitors instead. enough for starting current but much lighter in weight.


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## nineball76 (Mar 13, 2010)

You're slowly getting to my point. RESERVE, THAT'S ALL BATTERIES ARE FOR. For when you exceed your energy makers ability.


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## nineball76 (Mar 13, 2010)

You can't run a system indefinitely on batteries.


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> You're slowly getting to my point. RESERVE, THAT'S ALL BATTERIES ARE FOR. For when you exceed your energy makers ability.


 I don`t think your point contradict mine but the thing is that no amplifier drawing constant current unless sine waves playing.


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> You can't run a system indefinitely on batteries.


I can run 200A system on 70A alternator and good battery indefinitely, you can`t run 200A system on 150A alternator without battery. 
Anyway I made my point to the best of my ability and I`m off to bed.


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## nineball76 (Mar 13, 2010)

You can't run it on batteries alone indefinitely. But I sure as hell can run a 150a system on a 270a alt with no batteries indefinitely.


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## nineball76 (Mar 13, 2010)

Victor_inox said:


> I can run 200A system on 70A alternator and good battery indefinitely, you can`t run 200A system on 150A alternator without battery.
> Anyway I made my point to the best of my ability and I`m off to bed.


Man you don't get the point at all. Those batteries aren't making the energy, music being dynamic isn't pulling 200a all the time. Turn off the car and within a couple hours your fun dies along with the ability to start your car.


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## nineball76 (Mar 13, 2010)

It's measurable. Take a non regulated class whatever that makes 700 watts at 12.? And 1100 at 14.?..... Put on a sine wave and find your 1100 with the car running, disconnect the alt and immediately you'll be at 700 watts cause batteries aren't ever a 14v source.


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## TrickyRicky (Apr 5, 2009)

The battery is just there to turn on the vehicle...once the motor is firing then the alternator takes over and powers up the whole electrical. That simple, just as nineball stated that if you remove the alternator then the battery will instantly drain (especially if you have your engine on/firing) this is a clear indicator that the alternator is doing all the work and the battery is just there to crank the starter.

As for amplifiers, well lets keep this simple...(this applies to most amplifiers) higher input B+ voltage the higher the rails voltage which means a bit more power output.


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## Victor_inox (Apr 27, 2012)

Why don`t you people don`t buy a smallest battery to save weight or better yet bank of supercapacitors only to start your vehicle if battery is so unimportant.


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## nineball76 (Mar 13, 2010)

Victor_inox said:


> Why don`t you people don`t buy a smallest battery to save weight or better yet bank of supercapacitors only to start your vehicle if battery is so unimportant.


Weight savings isn't important to me. I have 3 vehicles, each one with a 250a or better alternator. One vehicle weighs 17,000# and has 8 agm 31 batteries, 4 for starting and running electronics with the vehicle off, the other 4 run a battery powered ac unit. Second vehicle weighs 9500# and also had 2 agm 31 under the hood for starting purposes and winch duties that EXCEED the alternators capabilites. Third is a car that already has a decently small agm 94r under the hood, this is also a diesel. Weight savings would be minimal and hardly noticed. 

In the first truck, the 250a was installed mainly to speed up recharging without prolonged idling. The car gets a big alt to power the stereo, with 2 added banks of 3000F supercaps. Also the 270a on the other truck, pretty much covers it's stereo without any added reserve necessary.


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## TrickyRicky (Apr 5, 2009)

Victor_inox said:


> Why don`t you people don`t buy a smallest battery to save weight or better yet bank of supercapacitors only to start your vehicle if battery is so unimportant.


What you mean "you people"? :laugh::laugh:...

To turn an engine of vehicles requires a lot of power, hence the cca ratings. Otherwise we would be using a ten 1.5v AA batteries in series to get around 15v to crank/start up engines. That would save plenty of weight and space 

Like stated before, the battery is just there to crank/start up the big engine. Once it's firing the alternator provides all the juice, that's why you'll never be able to run a vehicle without an alternator/generator (of course unless it's electric, even then it has generators)

A bank of supercapacitors cost just as much if not more than most vehicle batteries.


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## Victor_inox (Apr 27, 2012)

TrickyRicky said:


> What you mean "you people"? :laugh::laugh:...
> 
> To turn an engine of vehicles requires a lot of power, hence the cca ratings. Otherwise we would be using a ten 1.5v AA batteries in series to get around 15v to crank/start up engines. That would save plenty of weight and space
> 
> ...


 Give me a ****ing break Ricky. I can run ****ing vehicle without alternator for 10-12 hours easy. or 5-6 hours with moderately powerful system.
It`s troubling that you out of all people can`t grasp what I`m saying...


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## TrickyRicky (Apr 5, 2009)

Victor_inox said:


> Give me a ****ing break Ricky. I can run ****ing vehicle without alternator for 10-12 hours easy. or 5-6 hours with moderately powerful system.
> It`s troubling that you out of all people can`t grasp what I`m saying...


Really? How many batteries?

Funny how when alternators go out/fail it's impossible to keep a car running without the battery draining within a few minutes but yet you speak of HOURS! And ANYBODY who has had an alternator fail can tell you this. How is that even possible? 
The only thing am understanding that is coming from you is that you believe that removing an alternator or that an alternator is not needed or not the main power source of a vehicle's electrical system. 

A battery is needed while vehicles engine is firing because it acts as a filter for any AC spikes so it is not a good idea to remove it while engine is running. Just saying so you won't go trying it lol.


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## nineball76 (Mar 13, 2010)

He doesn't get it Ricky. My whole point was that batteries are not an energy source and he said that was ********. Show me 1 battery that makes energy on its own and this conversation will come to an end. They are for storage so the alternator can dump it's extra amperage into for when the alternator is not available or is being exceeded. While car is running, it's the alternators job to supply the electrical energy needed to operate the electronic devices of the vehicle and to keep the batteries topped off at 12.8v to be able to start the vehicle later when the alt isn't yet running. The ecm, lights, air conditioning, stereo, usb sockeye, etc are all being fed a 14+ voltage source. Batteries don't supply 14+ volts. They aren't capable of it. Fully charged, remove the alternator from the circuit and what happens? Batteries drop to 12.6 to 12.8 within minutes. They don't hold 14 until 1.2v is drained off. Because that 1.2v was all alternator. 

Victor keeps insisting on running a 200a system on a 70a alt and a good battery. In this scenario the alt might provide 20-30a of what the system needs and then the battery reserve kicks in, this causes voltage drop and is where a regulated amp comes into play. 

In my scenario the same 200a system on a 270a alt, every bit of amperage is provided by the alternator, at no point is there any voltage drop as it never need to dip into battery reserves for its supply. 


Another thing to think about, if Victor plays his 200a system full tilt for, let's imagine 10h straight. Then shuts his car off without having let his battery replenish while the system is off, he will be unable to start his car or it will be very slow to crank the next day. Because he was using up all his reserves in the battery. In my design, I can easily start my truck after the same 10h of full tilt because I was never using the battery to power my system. It stayed topped off while I enjoyed the fruits of a 14.1v electrical.


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## Zippy (Jul 21, 2013)

I hate to break this to you guys, but Victor is right. As long as the battery is in the circuit, it will be a source of power and be used. At initial start of a car the battery is the only source of power(alternator produces nothing) and starts the car. Once the car is running the alternator and battery provide power to the system(barring Honda MPG saving).

Think of it this way, if you have two power supplies for a computer and only one is plugged in, then you can only draw on that one. So now you start the computer. Let say now you plug the other in. Are you really expecting the entire thing to be drawing power from just one of them? If you are you have completely negated the entire premise of redundant power. A car is no different.


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## nineball76 (Mar 13, 2010)

Zippy said:


> I hate to break this to you guys, but Victor is right. As long as the battery is in the circuit, it will be a source of power and be used. At initial start of a car the battery is the only source of power(alternator produces nothing) and starts the car. Once the car is running the alternator and battery provide power to the system(barring Honda MPG saving).
> 
> Think of it this way, if you have two power supplies for a computer and only one is plugged in, then you can only draw on that one. So now you start the computer. Let say now you plug the other in. Are you really expecting the entire thing to be drawing power from just one of them? If you are you have completely negated the entire premise of redundant power. A car is no different.


You missed the point. A battery is not a source of energy. Batteries don't make energy as I first said that Victor so eloquently put it, is ********. Show me a battery that makes energy. They don't, never have never will. You can put a dmm on your inputs on your amp, and with the car running you'll see 14v. Guess what? Batteries aren't 14v! Know what is? That's right, the alternator, the thing that's actually converting the motors energy into electrical energy. Disconnect the battery with the vehicle running and you will still have 14v at your amps. Whether or not your Alt can support your amps is another argument entirely.


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## Zippy (Jul 21, 2013)

nineball76 said:


> You missed the point. A battery is not a source of energy. Batteries don't make energy as I first said that Victor so eloquently put it, is ********. Show me a battery that makes energy. They don't, never have never will. You can put a dmm on your inputs on your amp, and with the car running you'll see 14v. Guess what? Batteries aren't 14v! Know what is? That's right, the alternator, the thing that's actually converting the motors energy into electrical energy. Disconnect the battery with the vehicle running and you will still have 14v at your amps. Whether or not your Alt can support your amps is another argument entirely.


If batteries are not a source of energy then please explain to me how you are starting your car without one! Batteries are 12.5 volt for a reason and I'll try to explain that in a sec.

The computer example may not be the best example with this crowd, so let me put it an other way. Since the battery and alternator are wired in parallel, let's use a parallel example we all know. A Dual Voice Coil Sub! Let's say voice coil 1 is 1.97 ohm and voice coil 2 is 1.98 ohm. Since voice coil 1 is less restrictive(lower impedance) it should get 100% of the power according to you. If that were the case no one would ever use dual voice coil subs since the second voice coil would be nothing but dead weight adding restriction to its function. What actually happens is one receives more power than the other, but both receive power! If you disconnect either voice coil on the sub it still produces sound. Same applies to power sources producing power whether they be mechanical(alternator) or chemical(battery). 

Now the reason why car batteries are 12.5 V. With chemical power sources as they produce power they decrease the voltage they produce over time. So putting a 14.4 volt battery(they do exist) into your car would cause it to run down over time anyway. Once it was providing less power, the alternator would be providing more power and any excess power would allow the battery to recover some of it's charge(high idling). Also the battery designed to produce 14.4 volt would die a LOT sooner as a result of the excessive use since it would be trying to recover charge the entire time the engine is running. So by having the battery at 12.5 volt, more of the work load gets distributed to the alternator and you don't have to replace batteries every few months. But both still produce power into the equation. If you don't believe that power is being drawn from the battery, then put a current meter in series between the battery terminal and cable. You'll see current flowing when the car is running. If the battery in a car is not providing power, then how do new Honda's with variable on/off alternators run with the alternator off?


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## nineball76 (Mar 13, 2010)

Zippy said:


> If batteries are not a source of energy then please explain to me how you are starting your car without one! Batteries are 12.5 volt for a reason and I'll try to explain that in a sec.
> 
> The computer example may not be the best example with this crowd, so let me put it an other way. Since the battery and alternator are wired in parallel, let's use a parallel example we all know. A Dual Voice Coil Sub! Let's say voice coil 1 is 1.97 ohm and voice coil 2 is 1.98 ohm. Since voice coil 1 is less restrictive(lower impedance) it should get 100% of the power according to you. If that were the case no one would ever use dual voice coil subs since the second voice coil would be nothing but dead weight adding restriction to its function. What actually happens is one receives more power than the other, but both receive power! If you disconnect either voice coil on the sub it still produces sound. Same applies to power sources producing power whether they be mechanical(alternator) or chemical(battery).
> 
> Now the reason why car batteries are 12.5 V. With chemical power sources as they produce power they decrease the voltage they produce over time. So putting a 14.4 volt battery(they do exist) into your car would cause it to run down over time anyway. Once it was providing less power, the alternator would be providing more power and any excess power would allow the battery to recover some of it's charge(high idling). Also the battery designed to produce 14.4 volt would die a LOT sooner as a result of the excessive use since it would be trying to recover charge the entire time the engine is running. So by having the battery at 12.5 volt, more of the work load gets distributed to the alternator and you don't have to replace batteries every few months. But both still produce power into the equation. If you don't believe that power is being drawn from the battery, then put a current meter in series between the battery terminal and cable. You'll see current flowing when the car is running. If the battery in a car is not providing power, then how do new Honda's with variable on/off alternators run with the alternator off?


Drain a battery then wait for it to fill itself back up. Go ahead, let me know how that works out for you.


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> You missed the point. A battery is not a source of energy. Batteries don't make energy as I first said that Victor so eloquently put it, is ********. Show me a battery that makes energy. They don't, never have never will. You can put a dmm on your inputs on your amp, and with the car running you'll see 14v. Guess what? Batteries aren't 14v! Know what is? That's right, the alternator, the thing that's actually converting the motors energy into electrical energy. Disconnect the battery with the vehicle running and you will still have 14v at your amps. Whether or not your Alt can support your amps is another argument entirely.


 You don`t understand energy, yep that simple.
By your logic gasoline don`t make energy it`s purely storage.
Sun doesn`t make energy ?


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## Victor_inox (Apr 27, 2012)

Zippy said:


> If batteries are not a source of energy then please explain to me how you are starting your car without one! Batteries are 12.5 volt for a reason and I'll try to explain that in a sec.
> 
> The computer example may not be the best example with this crowd, so let me put it an other way. Since the battery and alternator are wired in parallel, let's use a parallel example we all know. A Dual Voice Coil Sub! Let's say voice coil 1 is 1.97 ohm and voice coil 2 is 1.98 ohm. Since voice coil 1 is less restrictive(lower impedance) it should get 100% of the power according to you. If that were the case no one would ever use dual voice coil subs since the second voice coil would be nothing but dead weight adding restriction to its function. What actually happens is one receives more power than the other, but both receive power! If you disconnect either voice coil on the sub it still produces sound. Same applies to power sources producing power whether they be mechanical(alternator) or chemical(battery).
> 
> Now the reason why car batteries are 12.5 V. With chemical power sources as they produce power they decrease the voltage they produce over time. So putting a 14.4 volt battery(they do exist) into your car would cause it to run down over time anyway. Once it was providing less power, the alternator would be providing more power and any excess power would allow the battery to recover some of it's charge(high idling). Also the battery designed to produce 14.4 volt would die a LOT sooner as a result of the excessive use since it would be trying to recover charge the entire time the engine is running. So by having the battery at 12.5 volt, more of the work load gets distributed to the alternator and you don't have to replace batteries every few months. But both still produce power into the equation. If you don't believe that power is being drawn from the battery, then put a current meter in series between the battery terminal and cable. You'll see current flowing when the car is running. If the battery in a car is not providing power, then how do new Honda's with variable on/off alternators run with the alternator off?


Now that is exactly right.


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## Victor_inox (Apr 27, 2012)

TrickyRicky said:


> Really? How many batteries?
> 
> Funny how when alternators go out/fail it's impossible to keep a car running without the battery draining within a few minutes but yet you speak of HOURS! And ANYBODY who has had an alternator fail can tell you this. How is that even possible?
> The only thing am understanding that is coming from you is that you believe that removing an alternator or that an alternator is not needed or not the main power source of a vehicle's electrical system.
> ...


 Yes, really. I tried that many times.


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## nineball76 (Mar 13, 2010)

All these batteries at their factory. After being filled with acid, the words coming out of his mouth just before I screenshotted this are, "this is where we electrically bring the batteries to life." But I thought they were making their own energy chemically. That's what you're saying. 










Coming back around to where I mentioned my scenario several times. A 150-200 stereo. A 270a alt. Remove the battery from the circuit, nothing changes. Stereo continues to play without issue, indefinitely. Until I turn the car off. Same scenario but no alt, just a battery. How long until things start to die? Amps will fry. How long did that take,, 2, 3, 4 hours? But let the batteries drain down to 10v, and then let them sit to recharge themselves because they make energy right?


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## nineball76 (Mar 13, 2010)

Victor_inox said:


> You don`t understand energy, yep that simple.
> By your logic gasoline don`t make energy it`s purely storage.
> Sun doesn`t make energy ?


Trying to turn things around like always . Gasoline would be a source of energy, the tank would be like the battery. Only for storage of the energy. Batteries aren't making the electricity that's inside them, if they did we wouldn't need the alternator.


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## Zippy (Jul 21, 2013)

nineball76 said:


> Drain a battery then wait for it to fill itself back up. Go ahead, let me know how that works out for you.


I have and guess what, they do recover to a point. Completely drain a new battery and then disconnect it for a week. Hook it back up and you can start your car off it again. Chemical source operate differently from mechanical ones.

Would you answer my question now: If the battery in a car is not providing power, then how do new Honda's with variable on/off alternators run with the alternator off?


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> Trying to turn things around like always . Gasoline would be a source of energy, the tank would be like the battery. Only for storage of the energy. Batteries aren't making the electricity that's inside them, if they did we wouldn't need the alternator.


 No I`m not turning anything around, Where battery get it`s charge is irrelevant for the moment.

I never stated alternators is not required for system to work properly I just reacted on blatant disregard for the truth.
battery is an energy source once that energy is stored. On the same parallel circuit you can`t separate where current came from.
Alternator job is to keep battery charged while current drawn from the circuit.
You should understand that given how many batteries your vehicles use. But it seems to me that your 250A alternators is a waste of money considering what energy capacity your batteries has.


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## Victor_inox (Apr 27, 2012)

Zippy said:


> . Chemical source operate differently from mechanical ones.


 That is correct, no manufacturer charging AA batteries .yet they are energy source.


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## Victor_inox (Apr 27, 2012)

nineball76 said:


> All these batteries at their factory. After being filled with acid, the words coming out of his mouth just before I screenshotted this are, "this is where we electrically bring the batteries to life." But I thought they were making their own energy chemically. That's what you're saying.
> 
> 
> 
> ...


 No that is not what I was saying. read it again.


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## TrickyRicky (Apr 5, 2009)

Nineball I don't think they will understand the simple logic and explanation you've provided. To those who think the battery provides power while vehicle is running/on then remove your alternator or keep a stock 60-70amp alternator to power up a 2000watt system, lets see how much voltage drop you get. Voltage drop is just as dangerous as a poor/bad ground, it causes semiconductors in amplifiers to work almost twice as hard (more current needed to keep producing same output....current creates heat).


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## Victor_inox (Apr 27, 2012)

TrickyRicky said:


> Nineball I don't think they will understand the simple logic and explanation you've provided. To those who think the battery provides power while vehicle is running/on then remove your alternator or keep a stock 60-70amp alternator to power up a 2000watt system, lets see how much voltage drop you get. Voltage drop is just as dangerous as a poor/bad ground, it causes semiconductors in amplifiers to work almost twice as hard (more current needed to keep producing same output....current creates heat).


 Would you run a car without battery or weak battery for that matter?
Why wouldn`t you, your alternator providing plenty of current.
Sometimes laws of physics slightly more complicated than simple logic.


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## oabeieo (Feb 22, 2015)

Wow I missed a good debate ....hot dam 


Anyway a 270A alt won't run a very large system with out a battery. You could run 15% of its output +\- .

A big alt doesn't put out continuous current. It depends on rpm and most importantly heat.
If it's hot it will do bursts and never get to 270A 

When it's cold it will reach its rated output for short bursts. It depends on the pcm and regulation. 

If you had 2500w and unhooked all batteries the system would have horrible whine and not get very loud. And could possibly **** up the alt.

How I know , my battery cable fell off while driving on last car once . 
It was surly enough to prompt me pull over quickly to take a look. Plus it's common knowledge on the web

Check out what zena says on there page it's very good 


Powerful alternators for auto sound


Read the whole thing please lots of info in the page the first few lines don't say much


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## TrickyRicky (Apr 5, 2009)

Victor_inox said:


> Would you run a car without battery or weak battery for that matter?
> Why wouldn`t you, your alternator providing plenty of current.
> Sometimes laws of physics slightly more complicated than simple logic.


First you need a battery to crank the engine, hence why vehicles have a large battery to begin with.

Second why wouldn't I run a vehicle with a weak or small battery? Well I guess you can go back to my "FIRST" explanation of the whole cranking of the engine statement.

Third a vehicle requires a battery because it acts as an AC filter/short, without it the alternator diodes can easily burn out and cause serious damage to the vehicles electronics and ECM.



So I still don't understand why you keep thinking that my argument is that "a battery is not needed/required and it can be as small or weak as possible" when I clearly KEEP making arguments ON WHY IT IS NEEDED!!! WTF DUDE? lol.

If you truly want to know what is proving the current/voltage when the vehicle is on/running/14.4v why not use a clamp meter and check what is proving the current.

Point A is your alternator, point B is your battery and point C is your audio system. 

All three of these points are connected of course, but with a clamp meter we can determine where the current is coming from when your playing sine waves as loud as possible without getting any voltage drop (keeping the voltage around 14v and the current consumption steady). You'll notice that there will be current coming from the alternator (between point a and b), and this current will be identical or close enough to the one coming from your battery (between point b and c)..why is that? if all the power is coming from the big battery shouldn't it be near 0amps between point a/b even with the car audio off, that would prove that the battery is in fact providing all the power need as you stated Vic.

Now if you can do this test and prove me wrong then I will gladly say I was wrong and that when the engine is running the 14.4v that is provided to the vehicles electrical system is actually because of the battery. Fair enough, or is my testing flawed?


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## Victor_inox (Apr 27, 2012)

TrickyRicky said:


> First you need a battery to crank the engine, hence why vehicles have a large battery to begin with.
> 
> Second why wouldn't I run a vehicle with a weak or small battery? Well I guess you can go back to my "FIRST" explanation of the whole cranking of the engine statement.
> 
> ...


point in question was is battery a power source or not.
I insist that it is and nine said it isn`t.
Somehow all this debate evolved from there.


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## magmun (Feb 17, 2021)

This thread is so relivent to my current situation mainly because I ve never really considered the voltage in a vehicle anything other that 12 volts. But apparently it s a bit more than 12 volts most of the time which is probably why you see the 14+ volt specs for amps💡 I guess I never thought about it, but when I see, over and over, amp specs for 14+volts, I had to understand why it wasn t for 12 volts.


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## diy.phil (May 23, 2011)

Sometimes it's 30V or 36V too for a split second (load dump situation) but modern vehicles behave better. Car electronics/circuit people have to be sure the circuit/parts can survive a voltage spike. Normally it's in the 12V to 15V range, and slightly lower when the battery is weak.


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## Kimo (Jan 17, 2021)

Victor_inox said:


> Would you run a car without battery or weak battery for that matter?
> Why wouldn`t you, your alternator providing plenty of current.
> Sometimes laws of physics slightly more complicated than simple logic.


Concider this, cars didn't come with batteries originally, cars were started by cranking the motor and in doing so, the spark needed to keep running was produced by what we now know as an alternator. Batteries were added later in order to not have to manually crank the motor over to start.


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## JohnnyOhh (Feb 19, 2015)

you can view the electrical system voltage directly on a lot of newer cars via the car's internal CAN comm network too. if you were curious.... you can look at it over time, temp, etc. This can vary car to car.

on some cars, you can see the voltage directly on the instrument cluster, depending on settings, etc. if your car doesn't do that, you can buy cheap OBD2 adapters that has Bluetooth and then you can plug this in and monitor the voltage on your cell phone via Bluetooth connection. (this is how i do it currently) here's a couple links.

Hardware:

"KITBEST OBD2 Scanner Bluetooth Car Diagnostic Code Reader Scan Tool for Android - - $12"



Amazon.com



Sofwtare/App:

"Torque Lite (OBD2 & Car) - - by Ian Hawkins - - Free & Pay version, I use free version"








Torque Lite (OBD2 & Car) - Apps on Google Play


Measure vehicle BHP & Torque Clear car OBD DTC faults, View data in Google Earth




play.google.com







magmun said:


> This thread is so relivent to my current situation mainly because I ve never really considered the voltage in a vehicle anything other that 12 volts. But apparently it s a bit more than 12 volts most of the time which is probably why you see the 14+ volt specs for amps💡 I guess I never thought about it, but when I see, over and over, amp specs for 14+volts, I had to understand why it wasn t for 12 volts.


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## Holmz (Jul 12, 2017)

Kimo said:


> Concider this, cars didn't come with batteries originally, cars were started by cranking the motor and in doing so, the spark needed to keep running was produced by what we now know as an alternator. Batteries were added later in order to not have to manually crank the motor over to start.


I thought they used magenteos?
And also in air planes.
And also old kick start 2-strokes?


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