# Dual alternator install?



## ScnicExcellence

I already have two brand new batteries one 650 cca an one 700 or 750 i think. I just got them. I have a 105 amp alternator that was rebuilt last year. I am waiting on the alternator shop to get back to me on a 160 to 200 amp alternator that i want ot install as a second alternator. so i would ideally have 305 amps or 265 amps. Depends on what they get me. 
I want to run dual alternators because i would really like to not have any dimming or power loss using the plow or the salter that i am putting on this week.

I don't need to be told that the 200 amp alternator will be enough, i have alreadyd ecided i want to put dual setup. The only thing i am looking for is info on how to wire them up. Would i just split the excitor wire to the second one, then run a new charge wire from second alternator to the second battery. Or just run a charge wire connecting the two alternators then run them to the bigger battery that is used for the plow and salter. Any help would be good. thanks


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## B&B

A couple issues you'll run into right away with your current plan...

You can't run two different sized alternators and then tie them together. The higher output alt will over power the smaller one thus causing it to do the majority of the work. The smaller one will just be along for the ride. Thus it's not doing a thing by being on there in the first place.

Second, you can't charge two differently sized batteries with two differently sized alternators with ANYTHING in the system tied together... including any ground connections which is nearly impossible.

Dual alt's and dual batteries is of course do-able but everything has to match perfectly. Even with the best matched components they can still cause their own issues with maximizing the life of the components.


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## ScnicExcellence

Well i wnet out and tested the two batteries and there is a bad connection between the two so i cleaned it up just for plowing today. I am going to replace the connections with new ones and i am thinking that a second alternator that is 105 or 110 amp whatever mine is now. Then install that as the second one. 

I thought that the different size alternators might cause a problem but didn't think the batteries mattered.


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## sweetk30

batterys need to be the same brand / size / cca specs / and age.

and read this here for high output alts. http://www.plowsite.com/showthread.php?t=92879


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## Thermos017

sweetk30;910170 said:


> batterys need to be the same brand / size / cca specs / and age...


not the case if you wire the batteries/alternators seperately. when you add a second alternator, and wire the two sepperately, it is the same concept as having two totally seperate rigs. you split the exciter to the two, and that is the only wiring they should have in common. your charge leads and ALL positive leads should be kept seperate between the two systems. the main battery should be wired just like a single battery setup from factory is. any common wiring between batteries should be removed from the system. run a charge lead from the second alternator to the aux battery. if your second alternator has a second wire in the plug for monitoring battery voltage you can run that either to the charge post on the back of the alternator or all the way to the battery. really doesn't matter, as the charge lead is going to have battery voltage at it at all times. if your alternator has this lead it MUST be hooked up. if you don't hook it up you will burn up your battery in a hurry. just remember the exciter wire (and of course grounds to engine and chasis) should be the ONLY thing in common between the two different charging systems.

here is a diagram, just in case i confused you.


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## Rat_Power_78

sweetk30;910170 said:


> batterys need to be the same brand / size / cca specs / and age.


x2 on this. Killed a brand new battery of the same size/brand/etc within 6 months when I paired the new one with a few years old one. Sucks to have to buy the same parts twice.


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## 2COR517

It's on my wish list Thermos......

Been there for a while


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## Thermos017

Rat_Power_78;915384 said:


> x2 on this. Killed a brand new battery of the same size/brand/etc within 6 months when I paired the new one with a few years old one. Sucks to have to buy the same parts twice.


the original post was about a dual alternator, not just about dual batteries. again, when you use a second alternator, or even if you're using a good battery isolater, the matched batteries don't matter. you only need matched batteries when you are using one alternator to charge two batteries, without an isolater or diodes, using a common connection between positive posts.

we are going on our 3rd season of a dual battery setup in a 97 silverado with an isolater. one battery is about 5 years old, napa brand, and 600cca. the other (aux) battery is 3 years old, schwabb brand, and i believe 750 or 775cca. i'm not positive i have the cca's right there, but i know it's at least a 150 difference between the two. after upgrading the charge wires to the primary battery last week the batteries are both charging quite nicely and we have yet to kill a battery or alternator with this setup.

if you wire your dual ALTERNATOR setup as shown in my diagram above, it doesn't matter if one is a 10 year old 500cca, and the other is a brand new, manufactured last week, 1000cca. as long as they are wired properly it DOESN"T matter.


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## mcwlandscaping

You can get that same amperage and even more out of one custom alternator for a hell of a lot less money than you would be putting into the setup your trying to piece together.


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## JD Dave

Our new 08 has dual alternators but I didn't even want them. My 02 has a 160 amp alternator and even with the hydraulic wing Ebling I never ran out of juice. I know you said not to talk you out of duals but I think you might have a problem somewhere else. You don't have happy hands do you?


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## 2COR517

mcwlandscaping;916215 said:


> You can get that same amperage and even more out of *one* custom alternator for a hell of a lot less money than you would be putting into the setup your trying to piece together.


That's the downfall - ONE alternator. With two isolated systems, if you have an alternator failure, you can bridge the two sides together and keep going. In this business, your alternator is only slightly less important than your engine or transmission.

As for the cost, it's not a big deal. It wouldn't be much more than a nice DB Electric unit. Just time to build the brackets more than anything. And I would rather have two $200 alts then one $400 alt.


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## Thermos017

EXCELLENT points 2COR. I've seen a lot of threads in the past couple days about charging systems. everybody wants dual matched batteries coming from one alternator. does anybody else consider repairs and replacement when (not if) one part fails? you are replacing TWO batteries instead of one (even if only one of them fails), if you use a parallel charging system. 

as a mechanic for the company i work at, one of my primary duties is to reduce maintenance cost and down time. There is no possible way i could justify to the boss that he needs to buy 2 $150 batteries, and replace both of them every time one fails. as opposed to one $80 isolator, and one $150 battery (leaving an $80 battery to run the truck), and only have to replace the one battery that fails. as far as down time, 2COR covered that one well too. if we had room for the extra alternator there would be no down time with the exception of the 10 minutes it takes to change the alternator. we could continue working off the one good one until our part arrived. unfortunately i can't convince the boss just yet that he needs to sacrifice his A/C for an extra alt.(damn ac doesn't work right anyways)


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## ScnicExcellence

JD Dave;916259 said:


> Our new 08 has dual alternators but I didn't even want them. My 02 has a 160 amp alternator and even with the hydraulic wing Ebling I never ran out of juice. I know you said not to talk you out of duals but I think you might have a problem somewhere else. You don't have happy hands do you?


I want the dual alternator hooked up like was stated to have one alternator run the plow battery and one to run the truck. It will not cost me alot more to run the dual alternator rather than the single bigger amp. The alternator will cost me $160 for the 160 amp and then to make the brackets and buy the new belt i am sure would not cost more than $30. I would rather spend $30 extra now and have a smaller chance of having a break down because i was running only a small amount of amps for what i have hooked up. As well if one does go then i got the other that i can just run a wire across the batteries and have it parallel again, take 5 minutes to do this.


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## ScnicExcellence

ok so i just got my price on the 180 amp alternator not the 160 and it is only $145 with core trade in. So i am keeping my 105 amp one and now going to junkers to get a scrap alternator for $10 to use as the core. Then getting the 180 amp alternator. I don't think i will be able to make the brackets before the new year so i am just going to run the 180 amp alternator and keep the 105 as a backup. if i like how it is working i will leave the second alternator out and run only the hih output one. if i think i could use a bit more juice then i will run the second alternator after new years. 

Gotta see how it works for me on christmas.

Never fails that there will be a snow event on one of those days.


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## ScnicExcellence

well i went to pick up the alternator. When i got there the guy raised the price a bit like $25 but the alternator he gave me runs at 198 amps apparently. i will be putting it in tomorrow, then to see how much of a difference it will make. 

how much of a difference has anybody seen with the 200 amp alternator with two batteries.


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## DRIFTER92

Anyone got pictures/links of a bracket for an OEM 145 Amp Alternator, with belt length for a 2006 Chevy 3500 6.6 D.Max/Allison? I have looked on the net and the only link i found i called a fax machine... The wife finds anything in 5 seconds on the internet and i can spend hours and know less than when i started!

Thanks!


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## gearhead

DRIFTER92;955187 said:


> Anyone got pictures/links of a bracket for an OEM 145 Amp Alternator, with belt length for a 2006 Chevy 3500 6.6 D.Max/Allison? I have looked on the net and the only link i found i called a fax machine... The wife finds anything in 5 seconds on the internet and i can spend hours and know less than when i started!
> 
> Thanks!


contact these guy's, they have a kit to install a twin set-up.
I just got a belt from them for a twin 145.

http://www.merchant-automotive.com/


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## Nasty-Z

ScnicExcellence;918481 said:


> I don't think i will be able to make the brackets before the new year so i am just going to run the 180 amp alternator and keep the 105 as a backup. if i like how it is working i will leave the second alternator out and run only the hih output one. if i think i could use a bit more juice then i will run the second alternator after new years.


Actually the brackets you need are probably already on your engine , the AIR pump mounting location makes a great spot for a 2nd alternator , you didn't mention which engine you have so :

Big Block Chevy :










Small Block Chevy :










FWIW , the two CS130 alternators are 145 amps a piece , and carge two batteries independently of each other , I also wired a cutoff switch inline so if one alternator goes bad I could run on the other one .

Just some ideas for you

TOM


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## RichG53

I do not see any advantage to running two separate Alts. and two separate Bats.
... No matter what you run off each one you are still running off of one Bat..
In stead of duel bats were you have more total amps . or reserves...
Unless I am missing some thing....


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## Nasty-Z

RichG53;957905 said:


> I do not see any advantage to running two separate Alts. and two separate Bats.
> ... No matter what you run off each one you are still running off of one Bat..
> In stead of duel bats were you have more total amps . or reserves...
> Unless I am missing some thing....


Hey , to each their own , you may be right , I may be right , who knows 

I know this way works for me , I like having one dedicated charging system for the plow , not having to draw 180 amps time after time , lift after lift , etc... while trying to also power the truck's electronics , wipers , defroster , heater , radios , you get the picture .

Like I said , it works for me :salute:

TOM


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## DRIFTER92

I know that after about 8 hours plowing i noticed my truck was getting a little tired. I've got dual batteries, 06 Silverado 3500 6.6, 145 AMP alternator. I checked the price for a bad ass 240 AMP but it was over $300. So let me see here... go get an OEM 145 AMP off ebay for $120 and a longer belt and a bracket so at the most $200 since i just need a picture to copy a bracket anyway. This does 2 things, no more dimming lights or worries. Also if one quits I'm not down. For $200 i dont see how it could be a bad idea at all? Unless im missing something?


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## 2COR517

RichG53;957905 said:


> I do not see any advantage to running two separate Alts. and two separate Bats.
> ... No matter what you run off each one you are still running off of one Bat..
> In stead of duel bats were you have more total amps . or reserves...
> Unless I am missing some thing....





2COR517;916581 said:


> That's the downfall - ONE alternator. With two isolated systems, if you have an alternator failure, you can bridge the two sides together and keep going. In this business, your alternator is only slightly less important than your engine or transmission.
> 
> As for the cost, it's not a big deal. It wouldn't be much more than a nice DB Electric unit. Just time to build the brackets more than anything. And I would rather have two $200 alts then one $400 alt.


Redundancy is the single biggest advantage IMO.


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## jimz2500

Here is what I did. 200 amp runs the plow and lights
....150 amp runs the truck
.....two seperate batteries also
.....made my own brackets
....found a belt at AZ.
....belt coverage on an alternator getting constant, high amperage drawn from it is important.
....200 amp alt($250),Belt($20),Idler pulley($12),wiring and steal($35)....not having to worry about not making money(Pricele$$)


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## 2COR517

Nice looking job. What's this?


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## jimz2500

Thanks 2cor57
hahahaha...the picture is very cluttered as I coudn't wait to take pictures.
The plow on the truck is an early Boss V-blade...
Chain lift,lol...
Those are the hoses heading fom the solenoid block out to the plow.


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## VPRacing

Nasty-Z;957715 said:


> Actually the brackets you need are probably already on your engine , the AIR pump mounting location makes a great spot for a 2nd alternator , you didn't mention which engine you have so :
> 
> Big Block Chevy :


I like this idea... Any chance you would have a belt size for this setup?

I have a 90 Chevy with the 7.4L and would like to put a 2nd alt on it. The factory alt gets tired after a 10hr shift so I want to beef up the system a little. Not even positive what size the factory alt is.


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## Nasty-Z

If you install it exactally as I have in the picture , it uses a 99.5"-100" belt , I use NAPA part # 25-060994, and have had no problems.

Factory alternator should be 105 amps on yours. 

The main alternator in my setup is a straight plate CS-130 at 145 amps , auxillary alternator is a left offset plate CS-130 again at 145amps . Left offset plate CS-130 can be found as original equiptment on a '94 C-3500 / 454. 

TOM


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## bchurch05

i have a duramax the has dual alternators and it works the tits. never draws the batterys down no matter what i am running i can take a picture of the setup and try and get a part number and belt length if you are still interested it is a factory set up from chevy. they make a bracket to add a second alternator.


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## VPRacing

Nasty-Z;990021 said:


> If you install it exactally as I have in the picture , it uses a 99.5"-100" belt , I use NAPA part # 25-060994, and have had no problems.
> 
> Factory alternator should be 105 amps on yours.
> 
> The main alternator in my setup is a straight plate CS-130 at 145 amps , auxillary alternator is a left offset plate CS-130 again at 145amps . Left offset plate CS-130 can be found as original equiptment on a '94 C-3500 / 454.
> 
> TOM


Straight plate - Left offset plate

Are you talking about the mounting holes?

When I got my truck it had a brand new factory alternator on it and I just happen to know a guy that has a brand new factory one for a 94 - 105 amp for $35 if I want it, has the mounting holes just like pictured.

Is there any major drawback to putting a 2nd 105 amp on it compared to swapping the factory one out for a 145 and buying another 145? They are roughly $200ea if I were to get them from a parts store.

Thanks for the info!


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## Nasty-Z

Yes , straight plate is exactally that , mounting holes are straight across fromne another, left offset plate is one who's top hole is offset to the left when viewed from the pulley end of the alternator,

No drawback at all , a 105 would be just fine, I built starters and alternators for a few years and still have some hook ups when it comes to good parts fo them, that's the only reason mine are 145+/-.

TOM


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## DRIFTER92

bchurch05;990215 said:


> i have a duramax the has dual alternators and it works the tits. never draws the batterys down no matter what i am running i can take a picture of the setup and try and get a part number and belt length if you are still interested it is a factory set up from chevy. they make a bracket to add a second alternator.


I posted this in another thread somewhere...

Dual Alternators on an 06 Duramax.
Well doing some digging i have found some info that i can share instead of asking questions all the time. If you've got an 06-07 Duramax here are the part numbers you need for the "ambulance" package.

15847291 New OEM Alt.. 145 Amp (EBAY) $100.00
98072072 Aux Pulley 18.00
11515769 Aux Pulley Bolt 4.00
97300657 Belt 3476mm 59.00
97356246 Aux Bracket 70.00
11516360 Aux Bracket Bolts 6.00 (3/4" too long) 
15306329 Connector with leads 18.00
---------------------------------------------------------------------------------------------
TOTAL: $275.00

Thought this might help people in my position save some time on getting this stuff if they were interested and see what i have in it. These are also 20% off GM std prices, find a buddy to get you the deal. How is it GM went out of business again??? lol BTW the "Ambulance Package" was $983.91 for all this being bought from GM.

I will NEVER put a belt on my truck again, NEVER. If you have a duramax go look and see why you dont want to. i actually cut a fin off the shroud just to get to the tensioner to release it... Is it really that big of a deal to add a few inches to a truck here or there? The pharmaceutical industry has it figured out but not GM?


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## B&B

DRIFTER92;990533 said:


> Dual Alternators on an 06 Duramax.
> Well doing some digging i have found some info that i can share instead of asking questions all the time. If you've got an 06-07 Duramax here are the part numbers you need for the "ambulance" package.
> 
> 15847291 New OEM Alt.. 145 Amp (EBAY) $100.00
> 98072072 Aux Pulley 18.00
> 11515769 Aux Pulley Bolt 4.00
> 97300657 Belt 3476mm 59.00
> 97356246 Aux Bracket 70.00
> 11516360 Aux Bracket Bolts 6.00 (3/4" too long)
> 15306329 Connector with leads 18.00
> ---------------------------------------------------------------------------------------------
> TOTAL: $275.00
> 
> Thought this might help people in my position save some time on getting this stuff if they were interested and see what i have in it. These are also 20% off GM std prices, find a buddy to get you the deal. How is it GM went out of business again??? lol BTW the "Ambulance Package" was $983.91 for all this being bought from GM.


Nice p/n list for others and thanks for posting it but you're price comparison with getting the dual alts as an option is a little skewed. The YF2 ambulance package included more than just dual alts, it also included a rather expensive G80 locking diff ($320 by itself) and a few other details specifically for fleet ambulance use. And also your $100 ebay alt is a rebuild/reman. Not what you'd receive in a new truck with the YF2 option.

If you wanted a truck with dual alts you'd simply spec it with the KD9 dual alt option by itself and only cost an additional $260. Just wanted to clarify.


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## DRIFTER92

BUT THEY SAID IT WAS NEW!!! :laughing: it works i dont mind  

The first one literally fell off the truck when i got it, it was all busted up, but they sent me another new shiny one its definately not used maybe defective then fixed but not used.


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