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Old 01-27-2019, 01:44 PM
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Keep throwing a low voltage code

Let me start this by saying I enjoy music. Everything from old rock, jazz, new hip-hop, rap, country ect.... If it's good, I listen to it. Now onto the low voltage code.....

2009 JKU. For over 3 years now I've had Rocksford Fostgate all around and a JVC head unit. 3-ways in the bar, 6.5" mids in the kicker panels(that was a fun install) and tweeters. So 6 months ago I decided to install a sub as well. Went with a 12" RF Punch and a 3000 watt amp so I don't have to worry about power and if I want to add another sub there will be no issues, only the sub is powered by the amp. Everything runs great, no grounding issues, speakers/sub run great, all installed properly.

Right after Christmas I got a low voltage code, I checked the voltage of my alternator, the battery, even my amp's/sub's capacitor and all said it was good. So I cleared the code then it came back 4 days later. At this point I checked all wiring and all fuses, no issues, cleared the code again. It came back again, there's 4-5 days between when I clear the code and it coming back. Unfortunately I forget the code but I will write it down when it throws again.

So the question is could this be related to the sub install or maybe my alternator is going out? OE alternator so maybe? I have a Optima Yellow top battery that's 2 years old.



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Old 01-27-2019, 03:24 PM   #2
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Optima batteries are nowhere near the product they used to be when they earned a stellar reputation. Johnson Controls bought them and moved the entire manufacturing line to Mexico several years ago where, in my personal opinion, their quality and durability took a major hit. I personally have had three Optima batteries in a row die prematurely and I won't use them any more.

It's possible your Optima is just no longer to develop the amps required by your subwoofer. I'd take it to a battery specialty shop and have them perform a "load test" which is the only way to know a battery's true health. Properly conducted, a load test places a major load on the battery for a minimum of 10 seconds while its voltage is monitored. The battery is bad if the voltage drops off too much during that test.

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Old 01-27-2019, 05:36 PM
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It's possible your Optima is just no longer to develop the amps required by your subwoofer. I'd take it to a battery specialty shop and have them perform a "load test" which is the only way to know a battery's true health.
That's what the capacitor is for.... it preloads the power to push to the amp and sub.... it's preloading fine. Also already did this before the sub because my winch was acting up and it turned out to be a loose ground. I have no issues with optima.
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Old 01-28-2019, 07:56 AM   #4
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I didn't see where you mentioned how loud you listen to music.


A capacitor is meant to get you through the occasional peak in the music as a buffer between the amplifier and battery/alternator. What is rarely mentioned is that it's not a fix all for an insufficient electrical system that's being taxed by a case of crankitupitus. If you listen at loud volumes, the capacitor doesn't have a chance to reload after the first few seconds and then is basically worthless after that.


As an academic exercise, I'd like to know the conditional threshold that throws the low voltage code. Is it caused from a burst, or sustained condition and at what voltage, etc? This might tell you a lot.
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Old 01-28-2019, 11:13 AM   #5
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Originally Posted by CManHugh View Post
That's what the capacitor is for.... it preloads the power to push to the amp and sub.... it's preloading fine. Also already did this before the sub because my winch was acting up and it turned out to be a loose ground. I have no issues with optima.
As a guy who spent most of his career in the technical side of the electronics industry, capacitors can only do so much. Not to mention with a good battery you don't need a capacitor to keep up with peak current demands like from a subwoofer amp. And not forgetting capacitors don't recharge instantly after responding to a peak current demand so they can't keep up with everything. We never needed external/aux capacitors for stadium, arena, or theater size audio systems as they have more than adequate power supplies.
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Old 01-28-2019, 11:37 AM   #6
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You say you have no issues with the Battery but yet are getting a low voltage code.
It is the battery that supplies the voltage, the alt recharges the bat as it is used but it is the bat that supplies the base voltage.


With everything running and the tunes turned down then you should see about 14v.
Anything less than 13.5 you have an issue.
I would always replace a bat and alt together, they work off of each other so much that when one starts to go the other isn't far behind.


Now the big question that hasn't been asked yet is when does the code actually happen?
While actually driving with the radio up or after it has sat, over night/over the weekend?
If its while driving then my guess is the alt can't keep up with the newly added amp.
How many 75amp fuses are on this 3k watt amp?
Do you know what the current draw is on it?
How many spare amps did your stock alt have left?
Not knowing what else you may have drawing current, lights, winch, etc etc...
And one single sub, 2ohm 4ohm or 8ohm, or even sub 2ohm if you spent some money...
Hope you left some money in the bank for a high output alt


If its after the Jeep has sat for a bit then its the battery, chances are one of the cells has gone, so its basically in limp mode, working for now but it'll die totally soon, all while over working your alt and burning it out also.
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Old 01-28-2019, 11:43 AM   #7
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Originally Posted by Jerry Bransford View Post
We never needed external/aux capacitors for stadium, arena, or theater size audio systems as they have more than adequate power supplies.

Get out of here with your shoreline 220v-440v $500k systems
I think one of your gens is running out of Diesel, better call in another tanker
Oh and I think I heard a Ground Loop
Careful touching that mic stand
Did you bring an extra throw rug
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Old 01-28-2019, 09:17 PM
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Thank you all for the responses. Next time it throws the code I will get it. I just remember the reader saying "Low Voltage".

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I didn't see where you mentioned how loud you listen to music.

As an academic exercise, I'd like to know the conditional threshold that throws the low voltage code. Is it caused from a burst, or sustained condition and at what voltage, etc? This might tell you a lot.
I'll say when no one is around I do listen to it very loud but the code is not thrown at this point. Most of the time it's been thrown driving to and from work while listening to talk radio with the sub turned nearly all the way down (amp came with a gain knob).

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As a guy who spent most of his career in the technical side of the electronics industry, capacitors can only do so much. Not to mention with a good battery you don't need a capacitor to keep up with peak current demands like from a subwoofer amp. And not forgetting capacitors don't recharge instantly after responding to a peak current demand so they can't keep up with everything.
Agreed. I believe the OE alternator might not be keeping up?

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You say you have no issues with the Battery but yet are getting a low voltage code.
It is the battery that supplies the voltage, the alt recharges the bat as it is used but it is the bat that supplies the base voltage.

With everything running and the tunes turned down then you should see about 14v.
Anything less than 13.5 you have an issue.
I would always replace a bat and alt together, they work off of each other so much that when one starts to go the other isn't far behind.

If its after the Jeep has sat for a bit then its the battery, chances are one of the cells has gone, so its basically in limp mode, working for now but it'll die totally soon, all while over working your alt and burning it out also.
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Now the big question that hasn't been asked yet is when does the code actually happen?
When not listening to music loud, usually just crusing listening to talk radio

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Originally Posted by screwlose View Post
While actually driving with the radio up or after it has sat, over night/over the weekend?
No, it'll sit there with no issues

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Originally Posted by screwlose View Post
How many 75amp fuses are on this 3k watt amp?
2 in-line

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Originally Posted by screwlose View Post
Do you know what the current draw is on it?
Haven't tested that, can I do that with my fluke?

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Originally Posted by screwlose View Post
How many spare amps did your stock alt have left?
Not sure how to test this or many spare amps are left over however, the stock is 140amps right?

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Originally Posted by screwlose View Post
Not knowing what else you may have drawing current, lights, winch, etc etc..
I don't run sub when using the lights and winch

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Originally Posted by screwlose View Post
And one single sub, 2ohm 4ohm or 8ohm, or even sub 2ohm if you spent some money...
4 ohm

Quote:
Originally Posted by screwlose View Post
Hope you left some money in the bank for a high output alt.
Should I get 160+amp alt? Can someone point me in the right direction for one?

Battery suggestions? I've had nothing but redtops and yellowtops for the past 10years with no issues. I actually took a 4 year old redtop(2012-2016) out of my truck and put it in my swamp buggy and have had no issues for 3 years.

Edit: After doing a bit of research I found the Mean-Green MG1388 200a alternator, would this work with stock belt or would I have to resize?
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Old 01-29-2019, 07:48 AM   #9
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2 75amp fuses, then thats not a 3k watt amp, I don't care what the box said, 3 would be more like it.
But with 2 that means that amp is designed to at most pull 150amps, normally prob in the 20-60amps range.

Best way to measure current is with an amp clamp, easy addon for your fluke.


The stocker alt should put out 140, but thats to also run your Jeep.
Normally a stock alt has about 20-30 spare amps available.


Check these guys out on the youtubes, they've been doing it a long time
https://www.youtube.com/user/fivesta...ereoinc/videos
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Old 01-29-2019, 10:55 AM   #10
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Id get the battery tested, but given your previous post I'm suspecting a battery or alternator problem. I'm not even confident that the stereo has anything to do with it.
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Old 01-29-2019, 05:30 PM   #11
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I believe the OE alternator might not be keeping up?
That's the battery's job, not the alternator. Otherwise we wouldn't be able to run big winches that can easily draw more than 400 amps which is well over 3X the output capacity of the alternator.

And despite all the car audio guys still claiming Optima Red Top or Yellow Top batteries are the way to go, they're not keeping up with the battery industry. Optima's battery quality took a giant nose dive after Johnson Controls bought them and moved the manufacturing down to Mexico. I'll say this again... I had three Optimas fail prematurely myself... two Yellow Tops and one Blue Top which is just a Yellow Top with different connectors.

With the large gauge power wiring you're running, as evident in your photo, you wouldn't be having the low voltage issue if your Optima battery was able to keep up.
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Old 01-29-2019, 06:13 PM
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2 75amp fuses, then thats not a 3k watt amp, I don't care what the box said, 3 would be more like it.
But with 2 that means that amp is designed to at most pull 150amps, normally prob in the 20-60amps range.

Best way to measure current is with an amp clamp, easy addon for your fluke.

[/URL]
Sorry I misspoke.... There's two inline 30amp fuses and 1 300amp fuse. It's a Soundbox kit that is rated up to 5500w peak


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Originally Posted by Jerry Bransford View Post
That's the battery's job, not the alternator. Otherwise we wouldn't be able to run big winches that can easily draw more than 400 amps which is well over 3X the output capacity of the alternator.

And despite all the car audio guys still claiming Optima Red Top or Yellow Top batteries are the way to go, they're not keeping up with the battery industry. Optima's battery quality took a giant nose dive after Johnson Controls bought them and moved the manufacturing down to Mexico. I'll say this again... I had three Optimas fail prematurely myself... two Yellow Tops and one Blue Top which is just a Yellow Top with different connectors.

With the large gauge power wiring you're running, as evident in your photo, you wouldn't be having the low voltage issue if your Optima battery was able to keep up.
Alright, what battery should I go with? Don't say Interstate because I had one of those fail on me before I switched to Optima. Also if the alternator should be pushing enough power to keep the battery from draining and throwing a low voltage code right?
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Old 01-29-2019, 06:52 PM   #13
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Alright, what battery should I go with? Don't say Interstate because I had one of those fail on me before I switched to Optima. Also if the alternator should be pushing enough power to keep the battery from draining and throwing a low voltage code right?
An Odyssey PC1500DT is very tough to beat, most including me consider it the best quality AGM battery available for our Jeeps. The Bosch Platinum is another great choice of AGM battery.

And alternators can't keep up with instant current demands like a battery can. It's the battery that has to be up to the task, not the alternator. That's how we can run winches that draw over 400 amps on heavy pulls with standard 117 amp alternators... it's the battery that is responsible for providing the vast majority of the power/amperes. The alternator can't keep up.

Or you could just turn the volume down a tad. If I had treated my ears better when I was younger, as a musician and a Vietnam vet, I wouldn't have tinnitus now together with needing to wear two hearing aids.
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Old 01-30-2019, 06:50 AM   #14
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And there are several reasons why they make dual battery kits and high output alts.
Hell when you get into the Pro level Stereo or any kind of radio system buss bars with 4 5 or 6 batteries become pretty common.
With only 2 30amp fuses, that amp isn't pulling much power.
And I'll 2nd the Odyssey and Bosch batts and also throw in Stinger.
A good trickle charger is never a bad idea to have as a backup too if you have a power outlet anywhere near where you park.
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Old 01-30-2019, 11:00 PM
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An Odyssey PC1500DT is very tough to beat, most including me consider it the best quality AGM battery available for our Jeeps. The Bosch Platinum is another great choice of AGM battery.

Or you could just turn the volume down a tad. If I had treated my ears better when I was younger, as a musician and a Vietnam vet, I wouldn't have tinnitus now together with needing to wear two hearing aids.
I will look into the Odyssey and Bosch. Like I said before the code has only been thrown when the system is turned down but I don't have the code so I guess we'll come to that road when we reach it. I was in the Marine Corps from 06-14, have tinnitus as well and was told I need hearing aids prior to getting out. I just listen to the music louder haha.
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