200amp alt, excessive headlight dimming. Bad battery? Flawed electrical?

[hollywood084 10+ year member]

I just installed a 200amp alternator on my 2005 jetta (old style), did the big 3 with some 1/0, and ran 1/0 power to the trunk. I have a new optima 34r red top. I'm running a 12" shocker super xtreme with an earthquake ph-d2. When I crank it up, the headlights dim real bad. On a steady tone, they stay dim, so I don't think it's the alternator reacting slow. They MAY brighten very slightly on a steady tone, but it's hardly noticeable, if anything at all. The dash will dim slightly also.

If I were to compare it to my old 95' beretta with the stock alt and 2 batteries, the dimming seems worse. This is all while driving. I have no idea what it could be.

I few idea's I have:

-bad ground at the amp (although I don't know why I'm even considering it :\ )

-car's computer limiting output.

-battery is bad. Doubtful because the car cranks over great, but, it was completely drained due to the old alternator going bad. Charged it with 12amps for about 30-60 mins, then 8amps the rest of the way.

-it's just the way it's going to be

I expect some headlight dimming, but not at the level it is now. Not to mention the dashboard.

But as I said, I really don't have a clue.

The first car off battery voltage I got was 12.28-12.35, it was not directly on the battery posts, but on the terminals connected to them. I turned the car on and got a 14.42-14.45 at idle and 2krpm, directly on the posts. Then I measured again directly on the posts with the car off and got a 12.53ish.

Additionally, something came on when the car was running, sounded like a fan (but it wasn't the radiator fan.) I'm pretty sure it was some secondary air intake thing, came from towards the bottom of the engine. I've read about it before but forgot what it's called. Anyways, the voltage dropped to the low-mid 12's then back up to 14 while it was still on I believe. I'm going to get some reading with the sub playing.

I disconnected the battery chassis ground and hooked up my charger with a 2amp charge and the charger reads 14.8 volts, and 80% charge and rising quickly. With my charger, the battery% display climbs very quickly until it get's to the actual level of the battery, then the display slows down to actual charging speed. Maybe there is a slight, but abnormal draw when my car is off?

15.2v and 88% is what it steadied at. Voltage is a little high according to the optima website, but there's nothing I can do about that.

Click to read more...

 

[goingdef 10+ year member]

One thing I know about those battery's is if you over charge them at all they will vent and become pretty much useless I had it happen to one of my yellow tops once, listen for a hissing around the little gray circles on top while it's charging, also a red top will not give you the same results as a yellow will the red top is not a deep cycle battery and can't take the same type of abuse that the yellow can take

 

[hollywood084 10+ year member]

One thing I know about those battery's is if you over charge them at all they will vent and become pretty much useless I had it happen to one of my yellow tops once, listen for a hissing around the little gray circles on top while it's charging, also a red top will not give you the same results as a yellow will the red top is not a deep cycle battery and can't take the same type of abuse that the yellow can take

I have no idea why I decided to go with the red over yellow. But what's done is done. The battery hasn't been over charged though. The charger will prevent it from happening also. It also has an agm mode.

 

[goingdef 10+ year member]

I have no idea why I decided to go with the red over yellow. But what's done is done. The battery hasn't been over charged though. The charger will prevent it from happening also. It also has an agm mode.

Well thats a plus you might be able to exchange it at the auto parts store that you bought it at if you wanted to try a yellow top they have never given me any problems over swapping out battery's

 

[hollywood084 10+ year member]

It's already down to 12.7 and still dropping no more than 2 minutes off the charger. Optima's site says between 12.6-12.8v though. I'll see if it goes back down to 12.3

 

[hollywood084 10+ year member]

It's at a steady 12.59-12.6 for about 2 hrs now. Other than the battery, what else might it be, if anything?

 

[hollywood084 10+ year member]

Ran some more tests today and last night. Last night with the system blasting with the car off, headlights on, I had slight to no dimming. Turned it on, it was dimming again.

Got home from work today, and the highest voltage at the terminals with the car running was 14.0v. With the headlights, fog lights, and a/c full blast I got about 12.5-12.6v. With the headlights off it was just over 13v. With the a/c off it was back up to 14v. With the car off it's between 12.5-12.6v. Very strange because I've seen 14.4v with the car running.

 

[smoka 10+ year member]

It sounds like your batt is going bad and also too small.

Unless you bump excessively with the car off then you should not have to put the batt on an external charger.

 

[smoka 10+ year member]

Last night with the system blasting with the car off, headlights on, I had slight to no dimming. Turned it on, it was dimming again.

That alt is bad too from what you just posted.

 

[hollywood084 10+ year member]

I'm hoping it's not the case. But it is strange that the battery alone will have minimal to no dimming, but the alternator power + the battery power dims a lot.

 

[ahole-ic]

I'm hoping it's not the case. But it is strange that the battery alone will have minimal to no dimming, but the alternator power + the battery power dims a lot.

That is not at all strange. The dimming comes into play when the voltage drops from 14v to 12v and the battery starts discharging. When running only on battery the voltage stays constant. Your lights are dimming badly because the a/c is on and it robs your electrical system of a lot of power. Turn it off and you won't have such a bad dip. Your battery is not bad and there is no indiction whatsoever that it might be. Your alternator is not bad and there is no idication that it might be. Just learn how to unburden your electrical system by shutting off everything you can before you turn your stereo up.

 

[ejschultz 10+ year member]

I'd say swap the alternator for another alternator. A 200 amp alternator should be able to handle that type of power. Also, 1st-optima-batteries.com is a great site to get Optima batteries from. I've purchased 3 from them in the past. I'd definitely do business with them again. I'm going to get a yellow top in my Jeep once the crappy Duralast in there takes a dump.

 

[hollywood084 10+ year member]

That is not at all strange. The dimming comes into play when the voltage drops from 14v to 12v and the battery starts discharging. When running only on battery the voltage stays constant. Your lights are dimming badly because the a/c is on and it robs your electrical system of a lot of power. Turn it off and you won't have such a bad dip. Your battery is not bad and there is no indiction whatsoever that it might be. Your alternator is not bad and there is no idication that it might be. Just learn how to unburden your electrical system by shutting off everything you can before you turn your stereo up.

I've already tested with the a/c off. In the test with the a/c on, the stereo was off.

 

[hollywood084 10+ year member]

I'd say swap the alternator for another alternator. A 200 amp alternator should be able to handle that type of power. Also, 1st-optima-batteries.com is a great site to get Optima batteries from. I've purchased 3 from them in the past. I'd definitely do business with them again. I'm going to get a yellow top in my Jeep once the crappy Duralast in there takes a dump.

Well, I wish it were that simple. But being with out a car, getting to work, and convincing the builder of the alternator to let me exchange is a different story :\.

 

[ejschultz 10+ year member]

What kind of alternator is it?