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Dual Battery Setup

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Chevykid350, Apr 18, 2003.

  1. Chevykid350

    Chevykid350 Registered Member

    Apr 2, 2002
    Likes Received:
    Elizabeth, Co
    Question for all of you guys. I have a 78 GMC pickup and I just got done welding in dual battery tays now my question is how do I wire them up??


  2. dremu

    dremu Officious Thread Derailer Premium Member GMOTM Winner

    Feb 27, 2000
    Likes Received:
    East of San Francisco
    Bunch o' posts about this -- do a search.

    Short answer: three basic options, in increasing order of cost and complexity.

    1. Parallel both batteries (plus to plus, minus to body) and be done with it. I've done this on my Burb -- I'm lazy, and I just wanted extra starting power.

    2. Isolate the batteries with a solenoid. This is how the factory set these up. The soleniod connects the aux battery to the main battery (and therefore alternator) when the key is on, hopefully meaning that the engine is running. Solenoid is $10-20 at your local NAPA and is pretty easy to wire. I have this on both my Blazers -- I can run accessories from the aux battery with the key off and kill it, and then crank the key and off we go.

    3. Isolate the batteries with a solid-state isolator (diodes). This is more expensnive but you can do some really cool things ... Hellroaring has switch boxes and stuff that go into this category of expensive and crazy to wire.

    Depends on what you wanna do with the batteries -- are you winching, lighting, or just starting in the cold?

    -- A
  3. rick88blaze

    rick88blaze 1/2 ton status

    Jan 24, 2003
    Likes Received:
    Knob Noster, Mo.
    painless wiring makes a wiring harness for the dual battery setup, check with summit or jegs they both carry it, sorry can't remember what it costs.


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