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Dual alternator install?

Discussion in 'Chevy Trucks' started by ScnicExcellence, Dec 16, 2009.

  1. ScnicExcellence

    ScnicExcellence Senior Member
    Messages: 352

    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
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    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.
  3. ScnicExcellence

    ScnicExcellence Senior Member
    Messages: 352

    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.
  4. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

  5. Thermos017

    Thermos017 Member
    Messages: 59

    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.
    Last edited: Dec 19, 2009
  6. Rat_Power_78

    Rat_Power_78 Senior Member
    Messages: 184

    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.
  7. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

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

    Been there for a while :(
  8. Thermos017

    Thermos017 Member
    Messages: 59

    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.
  9. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    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.
  10. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,194

    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?
  11. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    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.
  12. Thermos017

    Thermos017 Member
    Messages: 59

    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)
  13. ScnicExcellence

    ScnicExcellence Senior Member
    Messages: 352

    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.
  14. ScnicExcellence

    ScnicExcellence Senior Member
    Messages: 352

    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.
  15. ScnicExcellence

    ScnicExcellence Senior Member
    Messages: 352

    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.
  16. DRIFTER92

    DRIFTER92 Senior Member
    Messages: 124

    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!

  17. gearhead

    gearhead Member
    from ind.
    Messages: 57

    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.

  18. Nasty-Z

    Nasty-Z Senior Member
    Messages: 370

    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

  19. RichG53

    RichG53 PlowSite.com Addict
    Messages: 1,135

    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....
  20. Nasty-Z

    Nasty-Z Senior Member
    Messages: 370

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

    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: