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Big 3 Upgrade Question

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  • Big 3 Upgrade Question

    When upgrading the big 3, can I leave the existing ground wire and alternator wires connected or is it a must to disconnect them?

    I'd prefer to leave them in place and run a new wires to my second battery so as to make things easy to return to stock when selling the vehicle.

    Would this cause any problems?
    The specific setup I am considering is:
    stock battery with stock connections.
    0/2 run from stock battery + to second battery +.
    0/1 run from second battery + to alternator.
    0/1 run from second battery - to engine block.
    0/1 run from second battery - to chassis.

    Any experts with advice/suggestions on a more ideal setup to suit my needs?

    Thanks in advance!

  • #2
    If you want to do this you don't need the wire to the battery. Just to the Alternator. You SHOULD use a battery isolator of some sort. A high power solenoid designed to be on all the time is your best bet here. Should be active when the car is running.

    As far as the ground goes you could connect the wire directly to the engine block if you so desire. If you decide to hook this wire in your vehicle to the chassis then you will need to upgrade the wire from the chassis to the engine block to handle the extra power.

    No need to connect to the primary battery at all. But like I said, make sure you use some sort of isolator.


    • #3
      Grounds need not be disconnected other than the usual rule - ie, whenever dealing with hot wires (+12V), make sure the battery(s) ground is (are) disconnected.

      Though improving grounds are part of the Big 3, they are often done by ADDING new grounds as that does (or should) not impact vehicle ad equipment warranties. Plus ground redundancy is usually desirable.

      The battery connections should be improved if they are to carry bigger loads (ie, when the alternator is not charging (sufficiently)), or if their cabling voltage drop is to be decreased.

      And definitely a battery isolator for paralleled batteries. Though a manual or IGN +12V controlled isolator is better than nothing (provided the interconnect can handle the (shared) cranking current), and automated isolator is best.
      This can simply mean that the relay is controlled by the alternator's charge light circuit instead of IGN +12V etc. Search for the "UIBI" in this site.


      • #4
        Thanks to you both!

        Battery Isolator looks like the best bet for my situation. But alas! It appears I have much to learn. I'd like to do things the 'right' way, whichever way that may be...

        When searching UIBI I'm finding it hard to understand the basics of what is being proposed. Perhaps it is my ignorance of battery tech in general or specific to charging (or in this case the function of an isolator).

        Where is the Isolator typically installed?
        What connections need to be made?
        Alternator to the isolator and isolator to each battery +... is it that simple?
        What is a charge lamp and where is it found?

        To get a better understanding of grounding:
        I should connect each battery directly to the engine block but need not ground the batteries directly to the chassis?
        Does it matter if I use the same ground point to go from the battery to the engine block as from the engine block to the chassis?

        If it helps I can upload some pictures.
        And thanks for all the info. I've found such confusing (perhaps conflicting) information when I hit search.


        • #5
          Usually battery -ves (grounds) are to the chassis. The engine is also grounded to the chassis. FYI - the same was just stated on after somebody questioned the Big 3 and referred to "absolute ground" - a term that I find somewhat ludicrous.
          Some add a battery- to engine ground. That provides redundancy in case the engine to chassis or chassis to batt- is lost. It also further improves ground bonding, ie, decreases ground resistance.

          I sometimes ad the extra batt- to engine because despite most load grounds being body/chassis connected or maybe bat- connected, the starter motor is one BIG load that depends on the engine to batt- ground.

          Dual or extra batteries - think of it in 2 steps.
          First - the installation where you install a 2nd battery somewhere, ground its -ve to chassis, and connect its +ve to the main battery's +ve.
          That interconnection is usually a heavy gauge wire that has a fuse AT EACH BATTERY END as near each battery as practicable. Those fuses are to protect the cable in case it shorts to ground - you don;t want to melt the cable or blow the battery(s) and possibly (or probably!) start a fire.
          Hence stage 1 - a fuse and cable and fuse to the 2nd battery. And grounded to chassis, and/else an (extra?) -ve to -ve cable.
          That is a simple ADD-ON process. It involves no changes to the original wiring, merely the addition of new wiring.

          The second step - isolation.
          This is based on the philosophy that batteries should not be left connected in parallel unless they are being charged. (Or in some cases, being used for a long reserve time for a load.) If left permanently connected, premature failure of one battery will fail the other battery as well.
          The other reason is when you have a load running off the 2nd battery but you don't want the main battery to go flat.
          In both cases, an isolator is used to keep the batteries separated except when required or desired.
          This can be done with a heavy duty switch, though usually a relay is used.
          That relay can be manually controlled - whether thru IGN +12V, ACC +12V, an HU's remote amp turn-ion, or a separate switch, etc.
          But what if you forget to turn off the HU or amp or switch, or leave the IGN or ACC on? You may be unable to crank the vehicle.

          Hence automated battery isolators.
          Ignoring diode and MOSFET isolators, they uses relays (aka contactors, solenoids, etc).
          Essentially they try to determine if the system is charging, and - if it is - they join the batteries.
          Voltage sensing and "smart" isolators were developed for systems that had no charge indication per se - eg, stator systems as found in marine apps, and some RVs and motorbikes etc.
          They were also developed as a simple "add on" at he cost of expense and complication for systems that had charge indicators. They may also have been developed to dupe people out of their money by referring to crap like priority charging etc.

          Most cars and trucks have a charge indicator. It's called the charge light.
          Instead of having someone's complex auto-sensing voltage circuit with whatever cut-in and cut-out voltage and whatever delay times that connects to a relay, why not use the charge light circuit to turn on the same relay?
          Hence the UIBI - the "Ultimate Intelligence Battery Isolator".
          It's the same relay that (you'd want to or ) is being used by the voltage sensing or "smart" isolator, but it's connected to an existing circuit instead of some expensive circuit with dubious advantage.
          There are some dependencies - ie, you have to be able to find the thinner charge-Light wire that exits the alternator (or its regulator) usually labelled D+ or L, and it had to be able to energise the relay coil with its +12V. But limited L or D+ output capability can be fixed (buffered) with a smaller intermediate relay, or a transistor or MOSFET etc, and that should be far simpler a and cheaper than a voltage sensing circuit.

          Anyhow, hopefully you can now understand other info about UIBIs and isolators etc.
          The isolator is placed anywhere on the battery interlink between the 2 fuses. Usually it's near the main battery since that is close to the alternator.

          So, first install the 2nd battery with the 2 fuses (unless they are located next to each other or have physical security (no chance of shorts).
          Later add the isolator. That may be after you have determined the required capacity, or have sufficient funds, or realise what happens if one battery drags down the other.
          Later you should be able to add manual switches or other triggers if it's a UIBi or a voltage/smart isolator with an addition manual input (ie, energise for cranking or jump-start, or amplifier, or winching, etc).

          PS - here's a diagram UIBI or charge-light controlled isolator from the12volt's Battery Isolator choice!:
          Last edited by OldSpark; 10-22-2012, 02:35 AM. Reason: ps...