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ADD DEEP CYCLE QUESTIONS

Discussion in '3rd Gen. Tacomas (2016+)' started by edyuen888, Sep 6, 2020.

  1. Sep 6, 2020 at 9:17 AM
    #1
    edyuen888

    edyuen888 [OP] Well-Known Member

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    Apologies if this is covered already.

    I have a group 27 AGM deep that I want to put in the bed for my dometic.
    I want it to charge while driving and discharge 24/7 without discharging my starting AGM.
    Can I just hook it up in parallel to my main battery so it will get charged? And do I need to have an isolating switch so it dose’t drain the Starter batt?
    Just want a simple layout really.
    Any information helps thanks.
     
  2. Sep 6, 2020 at 9:30 AM
    #2
    JEEPNIK

    JEEPNIK Well-Known Member

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    Simplest was is to use a battery isolator switch. With the engine running the switch closes and allows the battery to charge. Once the ignition is switched off the switch opens and anything connected to the second battery can't draw power from the starting battery. Wiring is simple. The biggest thing to remember is to use a large enough cable to ensure that the battery is recharged efficiently.
     
  3. Sep 6, 2020 at 9:48 AM
    #3
    Stocklocker

    Stocklocker Well-Known Member

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    The batteries will drain together unless you employ some form of isolator to disconnect the two, or isolate one from the other electronically.

    Oversize the cables to the bed or you will never properly charge the second battery. Minimum size to consider would be 2AWG.
     
  4. Sep 6, 2020 at 10:44 AM
    #4
    edyuen888

    edyuen888 [OP] Well-Known Member

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    Ok so use a switch and large gauge cable!
    Is there overkill on cable or should I just go really really big?
     
    BigWhiteTRD likes this.
  5. Sep 6, 2020 at 11:52 AM
    #5
    Stocklocker

    Stocklocker Well-Known Member

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    There is no upper size limit, but there is a point of diminishing returns.

    Ideally you want the charging voltage at the starter battery to be the same at the aux battery. To achieve this you either need large enough cable to minimize voltage drop, or you need a DC/DC battery charger for the Aux battery, which adds unnecessary expense and complexity.

    Yes you do need a battery isolator switch or a solid state battery isolator. The switch units work better as they do not have any internal voltage drop like the Solid state isolator blocks do.
     
    BigWhiteTRD and edyuen888 [OP] like this.
  6. Sep 6, 2020 at 5:59 PM
    #6
    BigWhiteTRD

    BigWhiteTRD Official thread killer (only crickets remain)

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    I concur with the above recommendations.

    Below are the parts I used to do a similar job. Note, I also had a few added requirements for self jump-starting and dual battery winching in addition to not draining the start battery. (Note I am willing to pay a bit of a premium for 'good' wire). Items shown are not necessarily from best price source but were just handy.

    https://skycraftsurplus.com/10awg-nickel-plated-aircaft-wire-white-m227593-01-9-rp8049.html

    https://www.amazon.com/Blue-Sea-Systems-Automatic-Charging/dp/B001VIXLRO/

    https://www.amazon.com/Bay-Marine-Single-Terminal-included/dp/B07LC3Q4LD/
     
    Last edited: Sep 6, 2020
    edyuen888 [OP] likes this.

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