2nd alternator and battery

blazin97 · 03-18-2008, 01:08 PM

Ok so this is my first post on here so I hope you guys can be cool and help me. My problem is my lights dim really bad when I have my system up. I know the basics of this stuff but not all of it, yet.
I upgraded the big 3 with 4 gauge(Battery- to chassis, chassis to engine and alternator to battery+), got a 2 farad capacitor, and grounded amp and capacitor to 2 seperate spots on the chassis and the lights still dim bad.
I have heard of others putting in a second alternator and battery and want to do it to my truck. I got a 120 amp alternator out of my buddies DeVille and mounted it to where my a/c compressor was(got rid of a/c). Now I have to wire it up and that is my problem, the Caddy has the 3 wire. The wires are: red 10 gauge goes to starter solonoid, gray 14-16 gauge goes to idiot light on the dash, and red 14-16 gauge goes to ingition which switches on the alternators field windings. Now where can I hook up the 14-16 gauge red wire to so the alternator can charge the 2nd battery without overcharging it? Do I need something elso or what? Also I don't want a manual switch.
Thanks

tgraham · 03-18-2008, 01:56 PM

You need a battery isolator which is capable of handling two alternators.

frollo · 03-18-2008, 01:58 PM

good god are you powering a complete outdoor concert venue? can't help you on the other alternator though gl!

blazin97 · 03-18-2008, 02:33 PM

I was hoping to run it as its own system as alt to bat.

Quote: Originally Posted by frollo

good god are you powering a complete outdoor concert venue? can't help you on the other alternator though gl!

I have a 2 1000 watt amps plus other accessories.

Sonicxtacy02 · 03-18-2008, 02:38 PM

Quote: Originally Posted by blazin97

I was hoping to run it as its own system as alt to bat.

I have a 2 1000 watt amps plus other accessories.

that means nothing. Take it from someone who paid $$$ for a dual battery setup. Unless ur spending hours playing music in ya car with the car off there's no point to a second battery for car audio/electronics. If u still wish to go this route however all you need is said battery, a stinger200 isolater and a low gauge wire.

blazin97 · 03-18-2008, 03:33 PM

Quote: Originally Posted by Sonicxtacy02

that means nothing. Take it from someone who paid $$$ for a dual battery setup. Unless ur spending hours playing music in ya car with the car off there's no point to a second battery for car audio/electronics. If u still wish to go this route however all you need is said battery, a stinger200 isolater and a low gauge wire.

It will help with the lights diming and other accessories I want to run. Would 4 gauge be ok for the power wire or should I use the 0 gauge I have?
Would I wire that to the red 14-16 gauge that goes to the ignition? How low of a gauge? 14/16/18/20???

Sonicxtacy02 · 03-18-2008, 03:47 PM

Quote: Originally Posted by blazin97

It will help with the lights diming and other accessories I want to run. Would 4 gauge be ok for the power wire or should I use the 0 gauge I have?
Would I wire that to the red 14-16 gauge that goes to the ignition? How low of a gauge? 14/16/18/20???

No. Most likely it wont help you with your dimming options because you will not be feeding 2 battery's worth of energy into 1 "dimming" problem. It doesnt work that way. When the vehicle is on your alternator is pretty much the culprit of dimming issues, and adding an additional battery for it to charge wont help the problem it will potentially make it worse. If you're looking for something thats gonna assist with dimming try a capicator or correct whatever electrical flaw there is in the system (which could be a matter of a NEW battery or something like rewiring EVERYTHING). Two batteries will only benefit you if u plan on playing music with the car off.. period!

that being said .. i ran a 4 gauge and it was fine. For the ignition i used a 14 or 12 gauge wire.. i cant remember. YRMV

blazin97 · 03-18-2008, 06:18 PM

Quote: Originally Posted by Sonicxtacy02

No. Most likely it wont help you with your dimming options because you will not be feeding 2 battery's worth of energy into 1 "dimming" problem. It doesnt work that way. When the vehicle is on your alternator is pretty much the culprit of dimming issues, and adding an additional battery for it to charge wont help the problem it will potentially make it worse. If you're looking for something thats gonna assist with dimming try a capicator or correct whatever electrical flaw there is in the system (which could be a matter of a NEW battery or something like rewiring EVERYTHING). Two batteries will only benefit you if u plan on playing music with the car off.. period!

that being said .. i ran a 4 gauge and it was fine. For the ignition i used a 14 or 12 gauge wire.. i cant remember. YRMV

Thanks for the replies but I want this to be its own system. New alternator ran to new battery to stereo, not linked to the current alt and battery.

Sonicxtacy02 · 03-18-2008, 07:25 PM

Quote: Originally Posted by blazin97

Thanks for the replies but I want this to be its own system. New alternator ran to new battery to stereo, not linked to the current alt and battery.

ok then thats totally outta my realm. I dont know of anyone in this forum that have gone THAT far.. u'd need to talk to some big SPL guys for that i thnk

ozzy71 · 03-18-2008, 11:49 PM

3-wire is the way to go when adding a second alternator... keep this in mind though.. you will be dumping MPG like crazy.

That said-- let me try to help you instead of redirect you.

Which GM 3-wire alternator do you have? Or-- Exactly what car did it come out of?

AC Delco Rating Clocking Delco Part # *Lester catalog Pt#
10SI 63amps 3:00 321-39 7127-3
10SI 63amps 9:00 321-41 7127-9
10SI 63amps 12:00 321-43 7127-12
10SI 63amps 6:00 321-135 7127-6
12SI 94amps 3:00 321-266 7294-3
12SI 94amps 9:00 321-269 7294-9
12SI 94amps 12:00 --------- 7294-12
12SI 78amps 3:00 321-247 or 321-357 278-3
12SI 78amps 9:00 321-244 7278-9
12SI 78amps 12:00 321-249 or 321-254 7278-12

blazin97 · 03-19-2008, 02:41 AM

Quote: Originally Posted by ozzy71

3-wire is the way to go when adding a second alternator... keep this in mind though.. you will be dumping MPG like crazy.

That said-- let me try to help you instead of redirect you.

Which GM 3-wire alternator do you have? Or-- Exactly what car did it come out of?

AC Delco Rating Clocking Delco Part # *Lester catalog Pt#
10SI 63amps 3:00 321-39 7127-3
10SI 63amps 9:00 321-41 7127-9
10SI 63amps 12:00 321-43 7127-12
10SI 63amps 6:00 321-135 7127-6
12SI 94amps 3:00 321-266 7294-3
12SI 94amps 9:00 321-269 7294-9
12SI 94amps 12:00 --------- 7294-12
12SI 78amps 3:00 321-247 or 321-357 278-3
12SI 78amps 9:00 321-244 7278-9
12SI 78amps 12:00 321-249 or 321-254 7278-12

Thanks man, I believe it was a 87 caddy deville.

JC-S60 · 03-19-2008, 04:15 AM

You will need a voltage regulator for the separate cirquit, so the battery doesn't get overcharged (unless it's already integrated into the alternator).

Good luck!

Joachim

ozzy71 · 03-19-2008, 07:17 AM

I have never seen a 3-wire alternator that is not internally regulated.

blazin97 · 03-19-2008, 05:40 PM

Quote: Originally Posted by ozzy71

I have never seen a 3-wire alternator that is not internally regulated.

How do I know if its internally regulated? If it helps it of a mid 80's Caddy. Its already mounted on the truck so i can test whatever
Thanks

ozzy71 · 03-20-2008, 09:35 PM

If this unit indeed came off of a 1987 deville:

It is a 120amp unit and it is externally regulated.

Here are some photos of things to look for:

3-wire connector:

Rear-photo of alternator

photo of external regulator

Your regulator may already be on your alternator. Any chance you can upload a photo of your alternator?? I mostly need the rear of the unit.

Also, do you already have the 3-wire pigtail? Keep in mind the photos I am showing you are from an autoparts store's online information-- so I need you to verify that it is correct.

I built a battery isolator and installed a 2nd battery in my shoebox scion for $10... it works perfectly... and is easy to do.