batteries, 1200 watts, lights dimming

Hi everyone i have a question. I have a 1200 watt mono block amp that is pushing a single 12 at 1 ohm. And i have a red top optima and a 180 amp ho alternator up front. But my lights are dimming when playing my music up. Now my question is i was told the yellow top optima's are great battery's for car audio and wanted to know if just one of these battery's would be more then enough for my single 1200 watt amp or would i need a better battery.

Have you done the Big3 upgrade?

https://www.the12volt.com/installbay/forum_posts.asp~TID~73496~PN~1

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

yes i have with 0 gauge.

What's system voltage when this happens?

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I'm sorry i don't understand what you are saying.

Do you have a DMM (digital multi-meter) so that you can monitor DC voltage at the battery while the lights are dimming?

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

no sorry no i don't only thing close i can get to one of them which i know chance are it wont do the job is one of them voltage reading off a top of a cap.

That will work, but I don't know how accurate it'll be. Play the system to loud listening levels (where you encounter the lights dimming) with the lights on.
Now monitor the voltage and see where it bottoms out at.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

when you say bottom out you mean voltage starts to drop ?

Basically. You'll want to see how far it goes down. -Don't let it go down past ~12volts, though. If it gets too low, turn the volume down or whatever.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

ok so when i get it to where it stays over 12 volts how long do i leave the system playing at that volume or what do i need to do then ?

You don't want it to get down to 12volts. We need to see where it's dropping to.

If it goes too low, you'll need a larger alternator.

Are you sure your gains are set correctly?

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

a larger alternator really i figure 180 amp is more then enough for 1000 watts. well i did the gain by ear but i'm taking the car in tomorrow to have this car audio place set all my settings for me on the amp and deck and stuff. i just figure with 1000 watts i would need a 2nd battery or somthing ?

1000wRMS really isn't that much. Your "180amp" alternator should have no problem keeping up adequate voltage.

Did you ever see what your voltage was dropping to?

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

yeah i did but it was telling me 10 volts so i had to wait tell pay day to get me ameter. so with the car at idle head lights on and heater on it jumps from 13.2 to 14.2 volts and after a bit it will drop to 12.6v and back up to 13.2 but it stays between 13.2 and 14.2 most the time.

An ammeter? You you mean DMM or voltmeter? (Ammeters in cars are useless - except for telling you what demand is (or if wired as a traditional ammeter, your alternator's shortfall at that load and RPM).

The voltage at the battery or alternator should ideally remain constant (13.8-14.4V). Voltage at the amp then reflects losses...

Maybe your alternator is going out, I have a 70amp alternator and autozone battery that pushes a JL Audio JX1000 at 2 ohms (1000watts) and my headlights do not dim at all. I am going to a PowerBasturds alternator when I get $350 bucks.

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2004 Hyundai Sonata
Kenwood KDC-X599 HU
2-Sundown X-18D4
2-SQ Q4500.1
2-SQ Q90.4
1-Massive DBX4
8-Niche 5.25 mids
8-Niche Tweeters
4-Skar 8" mid-bass
OhioGen 220a alt
OhioGen 350a alt
156.0

the alternator is good i took it in and had it tested at a alternator shop and they said it charge fine. now my headlights don't dimm its the dash lights that do just thought i put that in for you. and another thing my last system i had which was 1 12 inch punch p1 sub off a rockford fosgate 300.1 amp the voltage jump up and down on my stock alternator as well.

Did you ever test the system voltage with a meter?

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Yeah i did lastnight at work with a headlights on and my heater on at idle. With the system on all the way up it drops down to 13.2v each time the bass hits and goes back to 14.2v. But after a while it will drop to 12.6v for a split sec and go back to 14.2v. But with the system turn down it stays at 14.2v and never moves even if im driving.

shadowm891 wrote:

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Yeah i did lastnight at work with a headlights on and my heater on at idle. With the system on all the way up it drops down to 13.2v each time the bass hits and goes back to 14.2v. But after a while it will drop to 12.6v for a split sec and go back to 14.2v. But with the system turn down it stays at 14.2v and never moves even if im driving.

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That could be many things, but first I'd check the ground return resistance and make sure it's less than one ohm.  Make sure the Big 3 upgrade is intact and all connections are tight and there is no corrosion at your battery.  Very likely your alt can't keep up with the load either because it is too small or it is turning too slowly.  Try upping your idle speed and if that works, you may want to change the alt pulley or upgrade to one with more output at idle.

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Alright ill check that out but i have a question. I was surfing youtube and i came across a 101 lesson thing and i did the math and it said i need a 100 amp per hour battery for 1200 watts. And the red top i have now is 50 amps per hour do you think this could be the problem. Btw the red top up front.

DYohn] wrote:

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...check the ground return resistance and make sure it's less than one ohm.

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That's the second time I have seen such a high figure...
Where does it come from? I know AC ground systems usually specify a max 1 Ohm resistance(sic - it should be impedance!)

1 ohm at 100A means a 100V drop. That is not possible in a 12V system.

Are you sure you don't mean 1 milli-Ohm else 10mOhm (for a 1V drop)?


shadowm891 - you do realize that a 180A alternator is NOT 180A at idle - maybe not even 100A?
Also some alternators are slower to respond than others.


Except for the Ohmage, I can only repeat what DYohn wrote.
If the dip occurs across the alternator, then it is the alternator.
Anywhere else is a distribution (wiring) issue.


And that battery size won't effect dips - they still have similar internal impedances and should supply adequate current when needed. The AH rating is a total capacity measure and does not (on its own) reflect it current or short-circuit current capability.

Yeah i understand im not getting 180 at idle i'm only getting 105 but to my car useing some of that 105 as well just not sure how much. All i know is my stock was 75amps and a car use 40% of that but im not sure if that is at idle or with car moving now.what gets me is i have a underdrive pully on it to so its moving but ill check my grounds and all.

Less than one ohm is just a good rule of thumb for car audio.  Ideally you want it to be zero (or at least less than the meter's ability to indicate) of course.

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DYohn] wrote:

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Less than one ohm is just a good rule of thumb for car audio. 

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So a 10V drop for a 10A audio load is acceptable?
I don't think so....

One Ohm for speaker wiring maybe, but NOT the power path.
I think there is some confusion over what that ROT refers to.

Please, of course you're right.  That is unacceptable.  Like I said, ground return resistance should be as low as possible,.  Zero is the goal.  0.1 ohms is typical.  But I always use "less than one ohm" as the rule of thumb when trying to help people troubleshoot via the Internet because 1) it makes them measure, which most people never do 2) who knows what kind of meter they may have? 3) who knows if they know how to use the meter properly to remove lead resistance from the indication? 4) it keeps the conversation going.  And remember this is DC 12V power, not AC.  Impedance is not part of the equation.

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It sounds like an "old Ohmmeter" rule - make sure the "meter" reads under 1 Ohm...". Alas these days with digital (DMMs etc) we should be more precise.

And the voltage drop will be V = I x R. I'm saying that to the novices so they can check what info they are given (ie, is 100A thru 0.1 Ohm reasonable? IE: V = 100A x 0.1R = 10V which is obviously not a good GND voltage drop in a 12V system!

As many know, I rarely quote or use resistances. I ask what a reasonable max voltage drop is, then calculate the R from V/I where the "customer" decides the V and should know the I (or power from which I can be guesstimated) - eg, 1V @ 100A => 1V/100A = 0.01 Ohms max resistance.
Besides which the voltage across something (like a GND path) is easier to measure than resistance - and more "practical" assuming that is at max else known Amps
IMO if a figure like "x Ohms" is stated, it should have its assumption (ie, max 1V drop or max 1A load etc).   

And yes - a minimal voltage drop (ie, minimum resistance).

Sorry if impedance confused things, but that was wrt to house earthing/grounding Standards (the point being that a ground stake 300m away is useless for lightning protection etc), and batteries which have internal impedances rather than an "internal resistance" - though that does not impact the sort of DC stuff we do here. (Dare I mention Bleeder's and OldFart's that suggest AC on a vehicle's +12VDC due to motors and SMPS dc-dc converters (USB chargers, big amps, PC & laptop supplies etc?)

Thanks DYohn. (I like your tease for conversation. $%$#@!!) (LOL)