Dual Alternators for Dual Battery Setup

Discussion in '80-Series Tech' started by FloridaFJ80, Sep 26, 2012.

  1. FloridaFJ80

    FloridaFJ80

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    Before I decide on the best route for my dual battery setup would be, i wanted to bring the idea of dual alternators for discussion.

    Mainly what I am trying to achieve is the following:
    • Seperate the OEM electronics from the added Accessories
    • Dont want to make any changes to OEM electronics schema
    • Retain factory functionality
    • Be able to run all accessories on second battery and be able to drain battery and be able to start vehicle from main battery
    • Be able to jump the main battery in case of discharge with jumper cables
    • In the event the main alternator goes, be able to charge main battery with second alternator

    While camping I like to have the radio on, and I plan on having a nice audio setup with amp and subwoofer. One of my concerns is since I dont want to make any changes, will the headunit draw enough power to eventually drain the main battery. All AMP's will be powered from second battery. Assume both batteries are Optima Yellow tops.

    In case of a Main battery drain, how could I from the cabin jump start the battery? I dont want to use jumper cables.

    Is there a way to charge the main battery from the second alternator, in the event the main ALT craps out, without unhooking and moving anything, a complete High availability redundant alternator system at the flick of a switch? Is this even possible?

    I think the benefits are interesting, if you could have a fully redundant charging system.

    Any ideas?


    [​IMG]
  2. Offroads4x4

    Offroads4x4

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  3. Otamiway

    Otamiway SILVER Star

    Hey Frank,

    I like your idea for the dual alternator and redundant setup. I am sure the electrical gurus will chime in.

    My current setup uses a Wrangler NW dual battery setup that does most of what you need (Start from 2nd battery and isolates them etc.)

    I have the Photoman bracket and under-drive pulley on a Sequoia 150amp alternator to handle my power needs for now. I am considering a 3rd battery for a future converter and rear winch

    Subscribed
  4. FloridaFJ80

    FloridaFJ80

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    Thanks Stu and Offroads4x4 for chiming in. I am sure there is a system out there particularly for what I want to achieve, and I agree with Offroads it would need to be a marine solution.

    I just think that we all invest so much money into a dual battery setup, but most don't address the need for a back up alternator. Most have it included as their parts backup. but if your out in the trail or in the middle of nowhere, you dont want to be stranded and if you have a backup alternator, performing some roadside fixes in the middle of the night.

    I plan to build my rig for overland travel, and hopefully in a few years I can travel south to Argentina and follow in DMC (expeditionamericas.com) footsteps.
  5. sprfrkr

    sprfrkr

    Messages:
    105
    IMHO, I'd rather upgrade the existing alternator to higher output rather than introduce another parasitic belt driven point of failure to the system. If you only want to run the radio and such, then you can run a cranking battery and a deep cycle battery which is used in boats. Turn to batter #2 while sitting without the engine on, run it dead if you like. Then switch to 1+2 to restart and recharge. Turn off #2 after a little while. There are automated solutions for this, but a manual switch is easiest and works just as well.
  6. ironhippy

    ironhippy

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    Location:
    NB, Canada
    I installed an aftermarket head unit in my truck and when wiring it up, I wired the head unit power to my aux fuse panel. I have the ACC from the head unit wiring harness wired to a on/off/on switch, so I can turn the radio from ACC to Off to Always on.

    So my headunit's constant power is always drawing from my fuse panel which is wired to my AUX battery.
    My stereo's ACC power is switched to come on with the ignition (stock ACC) or to come on when the switch is flipped to another feed from my fuse panel.

    This allows me to keep the stock head unit functionality which I use 90% of the time, but it also allows me to start my truck without turning on the stereo (ACC = off) or to turn on the stereo without having the key in the ignition (ACC = power from fuse) and the head unit only draws from the aux battery.

    It adds complications but something like that would allow you to wire up your head unit directly to your aux battery so you can listen to the radio without using your main (stock) battery at all.
  7. CycloSteve

    CycloSteve SILVER Star

    x2 on the BlueSea setup. No need for a 2nd Alternator, and debatable if you really need a larger alternator (though I did do the 150a Photoman/Sequoia setup). Higher amps on the alt only count when charging or running a heavy load such as a winch or a boat-load of aftermarket lights. When the truck is turned off alternator size does not matter. In your case the size of the batteries and reserves are much more important.

    http://www.wholesalemarine.com/p/BSS-7650/Blue+Sea+Systems+Add+a+Battery+Solenoid+7650.html?utm_source=feed&utm_medium=cpc&utm_campaign=google&gclid=CIS0yrXe07ICFaaDQgodU04AEw

    If you go with that or similar you can use the 2nd battery to start, or even combine two half-dead batteries to start.

    I built my dual battery setup as a separate "household" curcuit, which is much more like how boats are wired. Keeps things simple and isolated. I also like the idea above of a dual throw switch which allows the headunit to run on one battery or the other. Usually not running my radio in camp, but can see the attraction to wiring it that way.

    :cheers:

    Steve
    Last edited: Sep 26, 2012
  8. ironhippy

    ironhippy

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    Just to be clear, my headunit is always "running" off my aux battery (although wiring a switch to toggle would be simple enough)

    My switch is on the ACC or the "on" power wire. So when I toggle my switch, it changes when the radio will come on. By default my radio works like stock, turns on with the key, turns off with the key. I just wanted to the ability to turn the radio off completely (when trouble shooting or starting the truck a bunch, I don't want to constantly reset my headunit) or to have the head unit always on regardless if the key is in the ignition or not (this is nice when the doors might be open and I want to listen to the radio, don't have to worry about the annoying beep or worry about draining my starting battery)
  9. rusty_tlc

    rusty_tlc Dain Bramaged Member

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    Where do you stop the redundancy train?

    I've rarely been stranded by a bad alt, if you are keeping an eye on the charging circuit you can usually limp to some kind of resource. Just be sure to set up your electrical such that you always have the starting battery in reserve and you should be fine.

    A far more useful add on would be on board air which would most of us use on every trip.

    Even solar charging would be IMHO a better add on than a second alt.


    If your really hard core and really want a second alt make sure you can also use it as an On Board Welder, an internet search will quickly show you how this can be done.
  10. 86tuning

    86tuning

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    Yep. Toyota alternators are considered to be some of the best in reliability and longevity. They'll also give some warning before failing, at which point you should get a Toyota reman or new one, depending on budget.

    I'd do the dual battery setup for sure. But skip the dual alts and go with onboard air instead.
  11. Offroads4x4

    Offroads4x4

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  12. Tapage

    Tapage Club 4X4 Panamá SILVER Star

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    dual alternator were used in daily basis in Venezuela years ago .. but that was due to lack of reliability on aftermaket hi amp alternators .. and price .. ( importing it ) .. having a good main unit and good " isolator " will do what do you want without needing to mess with more wiring and another pulley belts etc ..

    just my .0002 cents ..
  13. kilrspd

    kilrspd

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    what about the idea of 2 alt. 1 for operation and one for welding purposes?
  14. IBCRUSN

    IBCRUSN

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    ding, ding, ding we have a winner!!! As stated the Denso alternators are as reliable as an alternator can get. If you're not going to install a York a second alternator setup as a welder would be very useful. Outside of a fabricating a bracket, converting a GM or Ford alternator is quite easy (Google weldernator). Couple that with some sort of a throttle control OEM or DYI and you're set. With a little practice you'll be able to safely repair and get yourself, your buddy or a broken Jeep back to civilization.

    Upgrade your existing alternator with a Sequoia alternator and go dual battery and you can do everything you're looking to with the added charging system.
    Last edited: Sep 26, 2012
  15. alia176

    alia176 SILVER Star

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    It seems like a simple solution could be employed in response to the OP's question but I could be wrong. I too run a stereo with a sub and all that while camping or sitting in the driveway for hours. Oh yeah, the Engel is running 24x7 while camping as well.

    Plan A

    I suggest doing the simplest thing first: run a group 31 as your main battery and experiment with it to see if you kill it using your mondo stereo system. Something like a PC2150 from Odyssey or a Group 31 DieHard Platinum battery. Why am I suggesting this size? Look at the spec: http://www.odysseybatteries.com/battery/pc2150.htm *** 205 min capacity at 25 amps *** I don't think your stereo system draws 25 amps but if it did, then the battery is good for 4 hours at that draw rate. If you still kill the battery, then do plan B.

    Plan B would be to go with two good size batteries and a dual battery charging solution of some sort. In my case, a group 35 for the main, a group 65 for the aux with Wrangler dual batt system. You could install a group 31 batt as your aux batt for all aftermarket needs and keep your current main battery as is.

    Thing of it this way, when you have two huge bath tubs, trickling water out of it for hours shouldn't be a problem.

    Adding a second alternator is not necessary IMHO. It creates more complexity and the cost may exceed either of my plans outlined above. Remember, our alternators use two belts so you'd have to come up with a similar solution for alt #2. How are you going to achieve this? Why two belts? It's because the alt requires enough power to probably overwhelm a single belt system and may end up slipping quite a bit under a heavy load. A serpentine belt would work too I suppose.
  16. rusty_tlc

    rusty_tlc Dain Bramaged Member

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    Great idea I wonder why it took so long for somebody to suggest it? ;)

    Sounds like a ton of work since you would need to convert everything else over to the serpentine.

    Personally I like a belt for each device, serpentine systems seem like putting all your eggs in one basket to me.
  17. Tapage

    Tapage Club 4X4 Panamá SILVER Star

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    I agreed .. but in the bright side you only need to carry one belt as spare ..
  18. rusty_tlc

    rusty_tlc Dain Bramaged Member

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    What happens when your AC pump seizes up? You listen to it howl until you can get to a replacement?
  19. Photoman

    Photoman SILVER Star

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    At one time I started to tinker with adding a serpentine belt. My thought at the time was for adding a second alternator or moving the alternator up higher, a hydraulic pump for a winch or hydro, or for oba. I sized and made a serpentine pulley for the front of the crank and machined and fabricated some of the other pieces. I ran out of time when I was fabricating the upper mount.
    To try to change to a single serpentine belt would mean converting the crank pulley over which is an expensive proposition along with everything else.

    Bill
    Serpentine pulley stuff 029.jpg Serpentine pulley stuff 023.jpg
  20. Tapage

    Tapage Club 4X4 Panamá SILVER Star

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    good point .. it never happen to me tho .. but I've got few tensioner bearings seized in my life ...

    So I guess every design have it strong and weak points ..

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