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dual batteries

Discussion in 'The Garage' started by big83chevy4x4, Jan 11, 2004.

  1. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    i want to put dual batteries in my k20. how have you guys made a mount under the hood for the second battery. i want to wire it so that i can switch it from one to the other and to both. any one have a wiring diagram of this. picd would be helpful also /forums/images/graemlins/thumb.gif
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I got a 2nd tray from a Diesel truck in the junkyard.

    And here's how I wired it.

    [​IMG]
     
  3. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    I took a regular passenger side tray, drilled out the spot welds, flipped the leg that goes to the wheelwell around, and welded it back together.


    To do what you want you're going to need a battery isolator, a 3 way switch (single pole dual throw), and a standard switch.
     
  4. bryguy00b

    bryguy00b 3/4 ton status

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    mind labeling some of that!?
     
  5. rick88blaze

    rick88blaze 1/2 ton status

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    got mine out of a diesel truck in a junk yard. also, check out here they've got a pretty good setup. i'll be going to that eventually. right now i've got this isolator made by surepower.

    Rick
     
  6. SF87K5

    SF87K5 1/2 ton status

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    my duals in my 79 were wired pos to pos and then both batts had there own ground. It worked grate, here is a pic of them.
    [​IMG]
     
  7. bryguy00b

    bryguy00b 3/4 ton status

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    so you ran them connected to each positive, and them grounded both of them seperatly. what does this setup alow you to do?
     
  8. SF87K5

    SF87K5 1/2 ton status

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    [ QUOTE ]
    so you ran them connected to each positive, and them grounded both of them seperatly. what does this setup alow you to do?

    [/ QUOTE ]

    Yes thats how I ran them. It alowed me to run stuff off one batt and the engine off the other. Plus it would charge both batts. It was cool cuz I could jumpstart myself. LOL /forums/images/graemlins/thumb.gif
     
  9. Muddytazz

    Muddytazz 1 ton status

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    So doing it that way, the main battery just runs the motor/stuff and the other battery just runs your other things like acc. lights, winch, etc? You don't get a drain?
     
  10. bryguy00b

    bryguy00b 3/4 ton status

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    so u dont need an isolater for this setup? and u cant switch from battery to battery correct? so then do they do that "dualing battery" thing when the engine is of?
     
  11. SF87K5

    SF87K5 1/2 ton status

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    Thats how my battery were when I bought the K5. I never had a problem with it. That is how I will be setting up my duals on my 85 also.
     
  12. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    You need to have a complete circuit to charge a battery. IE: the ground terminal of the battery must be connected to the ground on the alternator.
     
  13. SF87K5

    SF87K5 1/2 ton status

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    one was to the alt and the other to the frame rail.
     
  14. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    You need to have a complete circuit to charge a battery. IE: the ground terminal of the battery must be connected to the ground on the alternator.

    [/ QUOTE ]

    GROUND on a vehicle simply means hooked to the chassis somewhere. Every metal part of the vehicle is grounded and it makes little or no difference where you hook your grounds, as long as you get a good connection.
     
  15. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    The way he originally worded it he made it sound like the grounds were switched (which doesn't make sense, but I've seen stranger things).

    In his second post, the one I replied to, is where I got confused.

    In his third post (in reply to mine) he cleared up the confusion. It appears he's got them wired just like a diesel (in parallel all the time) with no battery isolation of any kind.

    The way he has his wired if there is a drain on the system that kills one battery it'll kill the other. He's not actually running his accessories off one battery and his engine off another. He's running everything off wherever the highest voltage is. When the truck is running, that'd be the alternator. When the alternator isn't producing more voltage than the batteries, that'd be whichever battery has the most voltage at its terminals at a certain current. This is due to internal impedances of the battery and how fast the chemical reaction can happen along with the resistance of the wire.



    I said ground on the alternator to make sure we're talking about the same thing. I was over-dumbing it down. Ground is relative anyway. Hell, often ground at your alternator and somewhere else in your truck is several hundred millivolts different.
     
  16. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    worded it he made it sound like the grounds were switched (which doesn't make sense, but I've seen stranger things).

    [/ QUOTE ]

    My ground is in a sense switched for the 2nd battery. If I had put the quick disconnect in the positive cable, when I disconnected it and threw it down on the frame, I'd have a fire! With the switch in the ground cable, I can disconnect one side of it with no worries.

    And you're correct, the way his are wired, nothing is isolated and nothing is specifically running off the 2nd battery.

    I don't really think that there's any reason to isolate a battery anyway. Trucks are wired from the factory with batteries in parallel, I can't see it as a problem, although I don't leave mine connected and park my truck for weeks at a time to see if I can kill my batteries. /forums/images/graemlins/rotfl.gif
     
  17. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    If you lived here, you'd run an isolator if you had two batteries. Even the diesel guys run isolators. It's better to have one battery dead instead of two. It sure would suck when an oxidized plate loses a chunk and shorts a cell and kills both batteries.

    My Dad had a diesel car that he parted out 15 years ago. It had a solenoid between the batteries with two fusable links coming off it going to the glow plugs. I was going to use it on my truck but I went and bought a Ford solenoid for $3.

    I just drew up in PSpice how I have my dual batteries wired. It looks kind of crappy because it's a jpeg but it'll have to suffice.

    [​IMG]


    There are zero splices. All connections are done with bolt-through ends that have been crimped and then soldered on. It is very important to solder everything. If I had a dollar for every rat's nest I've fixed that had shoddy splices and crimp on only connectors I'd have enough to buy me a winch. It's best to shrink tube everything but I don't have large shrink tube and only use electrical tape. Remember, when wrapping with electrical tape the thickness of the wrap should be NO LESS than the original insulator.

    You can make your own custom cable ends for large diameter wire using copper pipe. Find copper pipe that fits relatively snugly over the copper conductor. Buy a couple feet of it. Purchase some 60/40 solder if you don't have any. Cut off a 2" piece and crimp about 1" of it in a vice so it is perfectly flat. Drill a hole in the flat spot the diameter of the fastener you're going to use. Remember, the rule of thumb is to have close to as much copper left on each side of the hole equal to the radius of the hole you drilled. Now drill a small hole (1/8" will work) into the uncrushed part of the terminal but close to the crushed part. This will be used to fill the terminal with solder. Now stick the wire into the terminal all the way and use a punch to crush the pipe. I usually only use one punch mark but some people do another punch mark 180° away. Now use a propane torch and fill the terminal with solder. Don't forget to tin any leftover exposed copper.


    There are two main takeoffs at the positive terminal of the main battery: #1 The 2 gauge wire that comes off the battery to go to the solenoid then to the auxilary battery. #2 The 4 or 2 gauge wire that goes down to the starter.

    At the starter, there are now three wires connected to the large positive terminal: #1 The 4 or 2 gauge wire that comes from the main battery. #2 The 10 gauge or larger wire that goes to the alternator. #3 The 10 gauge wire that goes to the fuse that goes to the battery isolator that goes to the auxilary battery.
     
  18. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    i think this is waht im looking for. thanks
     
  19. bryguy00b

    bryguy00b 3/4 ton status

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    ok so it looks like u have to do some splicing in the wires at certain points right..what do u use to do that?
     
  20. bryguy00b

    bryguy00b 3/4 ton status

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    and the reason i want 2 batterys is for the cold winters..
     

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