View Full Version : Dual altenators on Vortec 350

01-21-2009, 12:27 AM
Has anyone done this? I've been toying with the idea for a few weeks. I know I can buy a 250 amp from DB Electrical, but I would rather have two separate systems. Since listening to my 155 amp Napa altenator growl like a tomcat for several hours after getting really toasty the other night and praying she would get me home, I am pretty serious about the the dual alt. project. Nothing fancy, probably a 12SI 100 amp or so, wired to the aux battery. I would switch the plow and sander and some aux lighting to this alt/batt. There is physical space to the left (from the seat) of the AC compressor. The upper radiator hose would run between the second alt and AC. Plenty of spots for brackets, which I presume would have to be fabricated. I have a welder friend. Between the two of us, we are pretty creative. The belt is going to be the trick. Easiest - bolt a pulley on the AC clutch or PS pulley. Second - bolt a pulley on the crank, but it doesn't look like a clear shot to the second alt. Third - longer serpentine belt. If I go over the rad hose, it would greatly reduce the contact area on the AC clutch. I'm not sure if the AC would stall without enough contact to the belt. Or try to add another idler under the rad hose between the AC and second alt. Any suggestions or pictures if you've done this would be greatly appreciated.

01-21-2009, 08:02 AM
How's about triples? :D

01-21-2009, 08:11 AM
How's about triples? :D

and how many batteries are in that truck B&B

01-21-2009, 10:30 AM
B&B - as usual, you are the man. Did you do that job? That looks like a newer 5.3 or 6.0. Does that truck have AC?

Sno Biz
01-21-2009, 10:51 AM
Now thats a sic set up... :eek:

01-22-2009, 01:12 AM
The first one was actually a store bought kit to run triples on the '99-current LS series engines. Have done one other one since..but I made the second one from scratch since I thoughtfully made templates from the store bought kit before I installed it. ;)

The truck had 5 12V electric pumps on it....pumped some kind of additive for asphalt on the job site. So with 5 pumps running continually for an hour at a time they needed something robust to supply the electrical demands. The alternators were rated at 150 amp EACH with three group 78 batteries mounted between the frame rails providing the reserve. Turned out to be a pretty cool setup and as far as I know they never had any issues with it.

With a little planning and fabrication work you can run dual (or triple) alts on just about anything, although with the current alternator technology out there now multiple alternators aren't needed as much as they once were. There's several companies out there now building 300 amp alternators that'll fit in the stock location.

01-23-2009, 10:04 PM
Low budget on my 94
works good
200amp powermaster for 950cca battery for plow
150amp upped CS130 for 850cca battery for rest of truck

01-24-2009, 07:15 AM
Jim - I like it.

01-24-2009, 07:12 PM
Thank you sir, it works very well.
I am thankful for friends with warm garages and extra eyes watching the project along.

02-05-2009, 08:26 AM
great info but i have some questions. sounds like most of you guys use the second alt to charge a second battery independent of the main/truck battery. how would you wire both alts to charge one bank of batteries(i have two batteries wired in parallel)

02-05-2009, 09:43 AM
I would presume that you could to that. It wouldn't be any different then when you jumpstart a vehicle and both vehicles are charging both batteries at the same time, after the second vehicle starts. I'm not sure though if one alternator would actually be doing all the work it it's regulator was set slightly higher. I suppose if you had one regulator controlling both alternators, then it would be fine. Maybe someone with more experience will chime in.

02-05-2009, 04:53 PM

if you can read through this you will find your answer.

Its an old thread from another who knows where forum, but informative.

02-09-2009, 07:55 AM
we just added a 220amp unit and a second battery to our 5.7L. works great. before it didnt matter if you raised the rpm's or not, the voltmeter would still drop fast while using the plow or raising the bed. now it drops very little and if you tap the gas pedal then the needle shoots right back up.