stock bat + yella top + 190a Alt and still dimming, WTF?

[mrjoeyjiffy 10+ year member]

Big 3, got 1/0 gauge running to the rear, stock bat in front, yellow top in the rear, running an earthquake 5000 on 2 jbl W12GTi's and I get BAD dimming when listening at full loudness. Will a battery isolater help this issue?

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[smoka 10+ year member]

An isolator will help extend the life of your batts, but it won't give you more power. How old are your batts? What voltage does it drop to?

You also might have a bottleneck at your ground location.

 

[ExpiredDrummer 10+ year member]

i second that bottleneck theory

 

[Mike465 10+ year member]

Well lets see, Your running a 5k amp at a 14.4 volt electrical system so using basic ohms law to find your current draw you get 347.22amps. You have a 190amp alt and two batteries. Your amp is pulling more current than the alt can produce for you electrical. Thats why you are still having dimming issues.

 

[mrjoeyjiffy 10+ year member]

my batt under the hood is actually brand new(my other one shitted out on me like 2 weeks ago) the yellow top SHOULD be a year and a half old, although after dealing with the assholes i got it from i wouldnt be surprised if it were used or something. My alternator does not put out full juice at idle, so at idle if i really pound on it it will go as low as 10v, if im driving and pounding on it it usually doesnt drop below 12.5 ish.

Can you expand more on the ground bottleneck theory? this is news to me, however I did move my amp after they installed it and got terrible alternator whine, even when i moved my amp back to the spot they put it in the alt whine was still there, only after grounding the rca's did the alternator whine go away. Is that indicitave of this bottleneck you speak of?

any help is appreciated.

 

[mrjoeyjiffy 10+ year member]

I KNOW this old pile of shit isnt a TRUE 5000w, i think my JBLs would be on fire.

 

[Mr. Slate 10+ year member]

Add another yellow top.

 

[Mike465 10+ year member]

my batt under the hood is actually brand new(my other one shitted out on me like 2 weeks ago) the yellow top SHOULD be a year and a half old, although after dealing with the assholes i got it from i wouldnt be surprised if it were used or something. My alternator does not put out full juice at idle, so at idle if i really pound on it it will go as low as 10v, if im driving and pounding on it it usually doesnt drop below 12.5 ish.
Can you expand more on the ground bottleneck theory? this is news to me, however I did move my amp after they installed it and got terrible alternator whine, even when i moved my amp back to the spot they put it in the alt whine was still there, only after grounding the rca's did the alternator whine go away. Is that indicitave of this bottleneck you speak of?

any help is appreciated.

Maybe this will help you understand it better.

Lets say you have a half full (or half empty) 1000 gallon container of water and your filling the container with a water hose. At the same time there is a fire hose connected to the bottom of the 1000 gallon tank allowing water to flow out of the tank. Lets say that it takes ten mins for the tank to almost empty.

Now if we go to a 2000 gallon tank with a water house hose still filling it up and a fire hose on the bottom of the tank allowing it to drain. This time it takes 20 mins for it to almost empty.

Now lets take that same 1000 gallon tank and replace the water hose for filling the tank to a fire house and the rate of fill is equal to the rate or dranage of the fire hose attached to the bottom of the tank. Now the tank remains the same water lever because the rate of fill and dranage is the same.

Just because you add more batteries to a system does not mean you are not going to get voltage drop. All you are doing is adding to the resurve and it slows the rate of voltage drop in the circuit. The only way you are going to be able to fix this if you get a much higher current alt or run a multi alt setup.

 

[99mitseclipse 10+ year member]

Check your ground, but I agree with the amp pulling more power. With the two batteries you only are putting in about (guessing on the stock) 80 amp hours. Your amplifier is drawing alot more, at minimum twice as much.

 

[smoka 10+ year member]

Well lets see, Your running a 5k amp at a 14.4 volt electrical system so using basic ohms law to find your current draw you get 347.22amps. You have a 190amp alt and two batteries. Your amp is pulling more current than the alt can produce for you electrical. Thats why you are still having dimming issues.

You are assuming the amp is a constant load, which it is not. Since music is dynamic, you will only be seeing a fraction of that load on average unless you listen to nothing but test tones etc.

The idea is to get enough batt capacity to handle the spikes in output while the alt can constantly charge the batts.

If that was a true 5k amp, then ya you probably should look into a bigger (or dual) alt with at least 3 group 31's. But if its more like 3kw, then that size alt plus 2 decent large batts in the back should be able to keep voltage up.

 

[mrjoeyjiffy 10+ year member]

so even with the upgraded alt and 2 batteries i still dont have enough? **** //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[smoka 10+ year member]

Can you expand more on the ground bottleneck theory? this is news to me, however I did move my amp after they installed it and got terrible alternator whine, even when i moved my amp back to the spot they put it in the alt whine was still there, only after grounding the rca's did the alternator whine go away. Is that indicitave of this bottleneck you speak of?

Your ground may be good, but you have to realize that you move just as much current through the ground connection as the positive. So if your ground passes through too many welds etc, then it might show low resistance when theres no power running, but when high current passes through it you may start to see a higher resistance at some point (hence the bottleneck), and that resistance will cause voltage drop.

Read this

http://www.caraudio.com/forum/showpost.php?p=6507801&postcount=8

 

[smoka 10+ year member]

so even with the upgraded alt and 2 batteries i still dont have enough? **** //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

Do you know the fuse rating on that big amp? It will help us determine the 'real' power of it.

Personally, if I were you, I would get at least 3 group 31 batts (all the same age if possible) in the back and just get rid of the front batt. IF that doesn't solve your problem, then a large or second alt would be needed.

P.S. An easy way to solve your grounding bottleneck problem (if that even IS a problem) is to just run an extra 1/0 of ground.