Wiring 2 alternators to completely separate batteries


Michael Poole

CarAudio.com Newbie
Oct 17, 2018
4
0
Hey guys I'm brand new to this forum and need a little help. I apologize up front if this question has already been answered. If so please shoot me a link. I've scoped the internet far and wide and can't find a good answer. Anyway, let's get to the point. I'm in the works of new audio build and I want to run a high output alternator straight to a battery bank that will power all of my subs (8 in total totaling 2700 watts rms) then I want to run a step above stock alternator to the start battery and high/mid range speakers. So here's the problem (or at least I think so). The alternator grounds to the engine directly through the mounting bolts so unless I make an insane alternator mount I can't avoid having 2 power sources sharing the same ground. 

Is this even a problem? Can you share the same ground or will you ultimately be connecting the batteries together? I want the systems to be completely separate but the more I think about it the more I think I'm not going to be able to do it. 

Any help would be appreciated. Sorry if the question is layed out poorly hard to think of the right words and terminology.

As a side note in case anyone is curious, the build I'm on is 2 15" JLW0v3's, 2 12" JLW0v3, 2 10" JLW0v3's, 2 8" JLW3v3, 2 6.5" JL C7 speakers, 2 1" JL C7 tweeters, 2 5.5" JL C5 speakers, and 2 .75" JL C5 tweeters. 8 subs 8 speakers as many different sizes as possible all on a pioneer p99 in a chevy astro. All JL amps as well except for the highs and mids only because I love pioneer for multi channel applications. 

 

Popwarhomie

Team Lethal Pressure
Jan 22, 2010
6,407
336
Florida
Oh god......2 15s, 2 12s, 2 10s, 2 8s, 2 6.5s.  Terrible idea.

BTW 2000 watts is not even close to needing two alternators. My single DC power 270xp runs my 5 batteries and 6 amps just fine.

 
OP
Michael Poole

Michael Poole

CarAudio.com Newbie
Oct 17, 2018
4
0
I'm all ears on why this is a bad idea, please explain. I want as many sizes as possible to focus specific hz levels to the speakers who play it best. best example is 8" subs vs 15" subs. 8s just don't play low frequencies as well as 15s and vice versa. Also the reason I want 2 alternators is because the hot idle amperage of the best alternator I can find (which is the 270xp from dc power inc.) is not enough to handle the max amps needed to power all of the subs, that mixed with the power needed to run the car, lights, spark plugs, heater, A/C, etc. not to mention the high end speakers. Total wattage is 3500 by the way. Another side note, this build is focused on sound quality not shake. Hence the p99, multiple speaker sizes, and crossovers.

 
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Popwarhomie

Team Lethal Pressure
Jan 22, 2010
6,407
336
Florida
I'm all ears on why this is a bad idea, please explain. I want as many sizes as possible to focus specific hz levels to the speakers who play it best. best example is 8" subs vs 15" subs. 8s just don't play low frequencies as well as 15s and vice versa. Also the reason I want 2 alternators is because the hot idle amperage of the best alternator I can find is not enough to handle the max amps needed to power all of the subs, that mixed with the power needed to run the car, lights, spark plugs, heater, A/C, etc. not to mention the high end speakers. Total wattage is 3500 by the way. Another side note, this build is focused on sound quality not shake. Hence the p99, multiple speaker sizes, and crossovers.
That is incorrect. Ive had 8" subwoofers all the way to 21" subwoofers.  An 8" subwoofer will play just as high and low as a 21". Its all in building the proper enclosure. Mixing subwoofer sizes causes cancellation.  Nothing sound quality about running 8 different sized subwoofers in 4 different boxes.   You must not be looking at the correct alternator companies. Excessive amperage will build a 400 amp large case alt for many different vehicles.    3500rms is nothing for a single alternator. 

 
OP
Michael Poole

Michael Poole

CarAudio.com Newbie
Oct 17, 2018
4
0
All of the enclosures are built to exact specifications.

I know where you're coming from.  enclosures, amps, and audio processors must be perfect to produce the right sound, but I have personal experience with 2 JL W0v3 10's and 2 JLW0v3 12's both in the bass wedge box from JL (so perfect enclosures) both have the same exact driver on the same exact power supply. The 12s did much better with low frequencies than the 10's this was in the same car at the same time. Saying that an 8" sub can do the same thing a 21"  sub can is like saying you can get bass from a tweeter if the enclosure is right (in my opinion) 

 

Popwarhomie

Team Lethal Pressure
Jan 22, 2010
6,407
336
Florida
All of the enclosures are built to exact specifications.

I know where you're coming from.  enclosures, amps, and audio processors must be perfect to produce the right sound, but I have personal experience with 2 JL W0v3 10's and 2 JLW0v3 12's both in the bass wedge box from JL (so perfect enclosures) both have the same exact driver on the same exact power supply. The 12s did much better with low frequencies than the 10's this was in the same car at the same time. Saying that an 8" sub can do the same thing a 21"  sub can is like saying you can get bass from a tweeter if the enclosure is right (in my opinion) 
What do I know about car audio. You clearly know more than I do.  Good luck with your build then. 

 

shredder2

Oldmang
Nov 19, 2017
2,341
251
Az
"perfect enclosures"
That above is quite an assumption... especially in a mobile environment.

Every enclosure I've ever designed has been a collection of compromises... some minor some large... some goal orientation,  others install specific but never mixing driver sizes... well... ever since the mid-80's  (high school).

Calling a basswedge "perfect" ... lol

Welcome to the forum, looks like you need some solid advice.

You debated solid advice with "personal experience"?.. this forum IS entertaining... good luck

 
OP
Michael Poole

Michael Poole

CarAudio.com Newbie
Oct 17, 2018
4
0
I believe you know a lot about car audio but you still haven't answered my original question. We can bicker all day and all night but it sounds like I'm going to have to learn the hard way. Maybe I'll catch you at a car audio competition and you can hear my system. Until then let's keep the thread to the original question. Thanks for the advice, I will be looking into the subject in depth before moving forward. A link to some information on mixing drivers and why it is bad would be highly appreciated 

 

Popwarhomie

Team Lethal Pressure
Jan 22, 2010
6,407
336
Florida
I believe you know a lot about car audio but you still haven't answered my original question. We can bicker all day and all night but it sounds like I'm going to have to learn the hard way. Maybe I'll catch you at a car audio competition and you can hear my system. Until then let's keep the thread to the original question. Thanks for the advice, I will be looking into the subject in depth before moving forward. A link to some information on mixing drivers and why it is bad would be highly appreciated 
Have you even been to a show and seen someone compete with mixed subwoofer sizes? Ive been going for 10 years now and have never seen anyone. Thats for a reason. Use the search feature here or even google "mixing subwoofer sizes" I also answered your alternator question. EA can make a 400 amp alt that will be more than enough to supply a 3500rms amp.

 

DirtyDuzit

Member
Mar 6, 2014
89
6
AZ
Popwar is right mixing subs is stupid.

To your original point no reason to make separate systems make a joined system.

 

nate0

Junior Member
Apr 18, 2018
176
21
Phoenix, AZ
It is ok to share the same ground. Beneficial though? Debatable. I do not really understand your concern...If you think otherwise, try it and see. 

Same for mixing Sub-woofer sizes.  Advice is advice, you take it or leave it, if you doubt or have a better idea try and see for your self. 

The depth of how sound, resonance, acoustics, etc. and all this stuff works is vast.  Folks all over the world learning better ways to build and achieve stuff that has never been thought of. I was remembering back in the 90s when I was even just scratching the car stereo scene's surface from my perspective seemed like I had seen it all.  Then I was reading a post from a 90's car audio veteran (I guess you could call them that...) who would build enclosures that would compliment or take into consideration the air space in the cabin of the vehicle.  Supplementing and using the vehicles resonance to achieve SQ, efficiency and loudness with what seemed like hardly any power...Calculating that stuff back then had to be done with out little gadgets that you can simply connect to your phone nowadays...

 It is very likely they gave a few pointers like above for a reason ;).

 

wew lad

wew lad inc
Mar 22, 2015
5,811
81
MA
"What is cancellation, for $500 Alex."

I have no idea how you plan to run 16 speakers off of one headunit and no processing. You're going to need a 16ch dsp and 4 4ch amps unless you butcher the shit out of everything

 
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