Time for a beefier alt, or do I need another battery?

[bananapehl777]

Hello all,

I'm brand new to this forum and I am really excited to connect with everyone else who's as obnoxious as I am driving their cars down the street! But I do have a question for those who are a bit more experienced than I am, as I don't want to waste money throwing upgrades at my system that it doesn't need.

I currently am running 1700W RMS in my 2005 Subaru Outback XT (it has all the bells and whistles, from heated seats to heated mirrors and wiper de-icer, basically there is a lot of factory electrical parts) and ever since I installed the system, I've had headlight dimming and sometimes at an idle, my engine RPMs will drop when the bass hits. Currently, I have a DC Power 270 AMP alternator, Big 3, and an Interstate MTP 35 as my only battery. My question is, is the headlight dimming and engine RPM loss due to the fact that my alternator is too weak for my system, or is my battery too weak for my system and I need to add a second one? I have a feeling I need to upgrade to a second battery, but others have told me that the symptoms I'm having is due to the alternator, and that adding a second battery will make it worse because it puts more of a strain on the alternator. I believe DC Power says at idle my alternator puts out 180 AMPs, but I'm not sure what that means, because I'm not sure if engine revolutions is the same as alternator revolutions (i.e. if my engine is idling at 700 RPM, is the alternator revolving at that too?) Any advice is greatly appreciated!

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[Bobbytwonames 5,000+ posts]

You really shouldn't be getting headlights dimming with your setup. Try a good sized AGM first. Just my $.02

 

[bananapehl777]

You really shouldn't be getting headlights dimming with your setup. Try a good sized AGM first. Just my $.02

Thank you, I may go with the AGM first and then go from there. When I was planning this system, I was trying to make sure that the electrical system wouldn't be a problem, yet here we are lol.

 

[Popwarhomie 5,000+ posts]

Halogen headlights are very sensitive to voltage drop. 1700 rms before rise shouldn't cause any crazy voltage drop. You shouldn't be seeing any drop with a DC power 270 as well.


I would guess your battery is dying.

You are going to have RPM drop. As the alternator will strain the engine when its working hard. In my 2010 I have to turn the stereo down to get on the highway.... lol

 

[bananapehl777]

Halogen headlights are very sensitive to voltage drop. 1700 rms before rise shouldn't cause any crazy voltage drop. You shouldn't be seeing any drop with a DC power 270 as well.


I would guess your battery is dying.

You are going to have RPM drop. As the alternator will strain the engine when its working hard. In my 2010 I have to turn the stereo down to get on the highway.... lol

I did think my battery was dying, so I just replaced it with a brand new one, but the same model, the Interstate MTP 35. The headlight dimming is still there, but not as bad I think. I think the addition of an AGM is going to help considerably. I may also install a voltmeter just to keep tabs on the system when I install the second battery. I have heard that halogens are very sensitive, but even the dash lights (which are not halogen) dim a little with bass notes. What my system really does not like is the punch bass where the subs are playing quick, short bursts. Makes my headlights into strobe lights almost lol.

 

[ThxOne Premium Member]

Remember, the alternator is NOT what is powering your stereo. When the stereo demands power it pulls it from the battery as the battery is designed to discharge large amounts of power quickly. The alternator will then kick in and slowly fill the battery back up and will only do this at a set rate, set by the voltage regulator. Pretty sure you did well upgrading the Alt as the stock one is about 110a.

So, you have plenty of alternator power to keep up with things and then some. You have purchased a new battery so that should not be an issue either. This "Big 3" you have done... what cables are going where and what size are they? They should be no smaller than 0awg and should be pure copper wires. How are these cables terminated? What battery terminals are you using? It is ok for headlights to flicker... not dim. A quick flicker when heavy bass notes hit is pretty normal with higher power if everything is good and tight. Dimming is a sign that there is a bad battery, too small of cables and or bad/poor grounds. Lastly an amp pushing a load it is not designed to push could cause the amp to draw too much current.

 

[Bobbytwonames 5,000+ posts]

Remember, the alternator is NOT what is powering your stereo. When the stereo demands power it pulls it from the battery as the battery is designed to discharge large amounts of power quickly. The alternator will then kick in and slowly fill the battery back up and will only do this at a set rate, set by the voltage regulator. Pretty sure you did well upgrading the Alt as the stock one is about 110a.

So, you have plenty of alternator power to keep up with things and then some. You have purchased a new battery so that should not be an issue either. This "Big 3" you have done... what cables are going where and what size are they? They should be no smaller than 0awg and should be pure copper wires. How are these cables terminated? What battery terminals are you using? It is ok for headlights to flicker... not dim. A quick flicker when heavy bass notes hit is pretty normal with higher power if everything is good and tight. Dimming is a sign that there is a bad battery, too small of cables and or bad/poor grounds. Lastly an amp pushing a load it is not designed to push could cause the amp to draw too much current.

It always goes back to math for the most part. Variations in cars is a factor, but math is math. Do your math and adjust accordingly. Every car is different. My car was a unicorn. Modern cars have a lot of **** going on with computers and stuff. "It's better to be a 1/2" too big than a 1/2" too small," That's what she said.

 

[yamomluvsme]

Remember, the alternator is NOT what is powering your stereo. When the stereo demands power it pulls it from the battery as the battery is designed to discharge large amounts of power quickly. The alternator will then kick in and slowly fill the battery back up and will only do this at a set rate, set by the voltage regulator. Pretty sure you did well upgrading the Alt as the stock one is about 110a.

So, you have plenty of alternator power to keep up with things and then some. You have purchased a new battery so that should not be an issue either. This "Big 3" you have done... what cables are going where and what size are they? They should be no smaller than 0awg and should be pure copper wires. How are these cables terminated? What battery terminals are you using? It is ok for headlights to flicker... not dim. A quick flicker when heavy bass notes hit is pretty normal with higher power if everything is good and tight. Dimming is a sign that there is a bad battery, too small of cables and or bad/poor grounds. Lastly an amp pushing a load it is not designed to push could cause the amp to draw too much current.

the alternator is a generator except its output is DC. it can and will power everything and its constantly charging. voltage sag is the problem capacitors are ideal for this situation. put a small cap inline with the lights. or get a cap bank or VERY low esr battery. deep cycles have a much higher ESR. don't use them for car audio

 

[n2audio 5,000+ posts]

Remember, the alternator is NOT what is powering your stereo. When the stereo demands power it pulls it from the battery as the battery is designed to discharge large amounts of power quickly.

Is that a typo? Because anyone familiar with the basics of automotive charging systems knows the alt is always the primary source when the engine is running.

 

[ThxOne Premium Member]

It is not a typographical error. To prove my point, remove your battery and start your car. The alternator is like a battery tender/charger in a way when the vehicle is running. Which is why it has a voltage regulator. When it senses the drop in voltage (from the battery) it will supply more power to the battery to bring it back up to the correct voltage. The battery is what is connected to the fuse panel, not the alternator because the battery is supplying the power, the alternator is maintaining the battery. Can an alternator run a car, sure, but that is NOT its job.

 

[ScottyBoyBasshead]

Hello all,

I'm brand new to this forum and I am really excited to connect with everyone else who's as obnoxious as I am driving their cars down the street! But I do have a question for those who are a bit more experienced than I am, as I don't want to waste money throwing upgrades at my system that it doesn't need.

I currently am running 1700W RMS in my 2005 Subaru Outback XT (it has all the bells and whistles, from heated seats to heated mirrors and wiper de-icer, basically there is a lot of factory electrical parts) and ever since I installed the system, I've had headlight dimming and sometimes at an idle, my engine RPMs will drop when the bass hits. Currently, I have a DC Power 270 AMP alternator, Big 3, and an Interstate MTP 35 as my only battery. My question is, is the headlight dimming and engine RPM loss due to the fact that my alternator is too weak for my system, or is my battery too weak for my system and I need to add a second one? I have a feeling I need to upgrade to a second battery, but others have told me that the symptoms I'm having is due to the alternator, and that adding a second battery will make it worse because it puts more of a strain on the alternator. I believe DC Power says at idle my alternator puts out 180 AMPs, but I'm not sure what that means, because I'm not sure if engine revolutions is the same as alternator revolutions (i.e. if my engine is idling at 700 RPM, is the alternator revolving at that too?) Any advice is greatly appreciated!

Yeah, you should add an XS Power battery. I got the D3400 and my headlight dimming is much more faint, but I've heard that if you got halogen headlights, it's gonna be inevitable. Your amp demands so much power that you're gonna see it in the headlights. If u got a upgraded alt, then a agm will work wonders for ya. I'm running 2000 watts on a factory 150 amp alt and xs power d3400 agm and seen a major difference. But, I still technically should get an alt. Just don't wanna spend the money.

 

[BCotrell]

Is that amperage rating 180 for 700 rpms? The newer Subarus tends to be on the tail of gutless unless you have their teenager cars (for the sake of efficiency they promote) which correlated to generally lower idle rpm than a ho alternator may be designed for.

anyways, if you’re listening to the stereo with engine on disregard posts nerding out on alt/battery stance...car is on alternator is providing more than enough amperage to feed a 1700 watt amp musically

-Are Big 3 grounds all good? What wire you use?
-at the amp what is the voltage (Drop) from baseline(14 ish with car on) that you’re seeing on when you have music up and car is on?

 

[n2audio 5,000+ posts]

It is not a typographical error. To prove my point, remove your battery and start your car. The alternator is like a battery tender/charger in a way when the vehicle is running. Which is why it has a voltage regulator. When it senses the drop in voltage (from the battery) it will supply more power to the battery to bring it back up to the correct voltage. The battery is what is connected to the fuse panel, not the alternator because the battery is supplying the power, the alternator is maintaining the battery. Can an alternator run a car, sure, but that is NOT its job.

This is wrong. Totally and completely wrong.
You have NO understanding of how sources of electrical power work.

 

[ThxOne Premium Member]

This is wrong. Totally and completely wrong.
You have NO understanding of how sources of electrical power work.

If you say so.

 

[n2audio 5,000+ posts]

If you say so.

You should read and understand this: http://www.bcae1.com/charging.htm
Doesn't get much more basic than that.