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dual battery set-up

Discussion in '40- & 55-Series Tech' started by darkman, Nov 5, 2003.

  1. darkman

    darkman

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    I have just installed a second battery box in my 40 with the intent of installing a second (auxiliary) battery. I am wondering about the best way to wire this up.

    I noticed an auxillary battery kit on the Man-a-fre page; however, it seems a bit expensive for me.

    I am looking for a way to charge both batteries but have the auxillary battery capable of being isolated ....

    Any ideas would be appreciated

    Mike
     
  2. dd113

    dd113

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    NAPA sells the isolators for around $35. Buy good quality wireing and follow the instructions.
     
  3. FJAfrica

    FJAfrica

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  4. hammerhead

    hammerhead

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    I used a battery isolator relay, acquired at the local parts house, that resembles a ford starter relay. I can run the camp lights and stereo till the deck won't play anymore and still start the truck no sweat. As soon as I do it's business as usual.
     
  5. MarkFJ40

    MarkFJ40

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    I thought those parts store isolators got burnt up by winching ?
     
  6. dd113

    dd113

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    [quote author=MarkFJ40 link=board=1;threadid=7176;start=msg59900#msg59900 date=1068151417]
    I thought those parts store isolators got burnt up by winching ?
    [/quote]

    Good point. I have used the set up while winching with no issues but I can see where it might be an issue.

    FJAfrica: can you explain how the charging diodes work (theory) and what size type are needed? The disconnect switch is just a throw switch?
     
  7. gkhal1

    gkhal1

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    I went with the painless wiring dual batt. 250amp current control. tho, one could get all these components separately.
    I'm going to add a marine batt. switch somewhere to be able to cut all power and fully disable the pig. And maybe put a marine 2 batt. switch (3 position) on the winch to give me ability to pick which batt. to use when winching.

    anyone run the painless kit?
     
  8. arutgers

    arutgers

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    Theory: diodes conduct only in one direction; not in the opposite direction. In the diagram current can flow from alternator through each diode to the batteries. Current cannot flow from one battery to the other, because this is blocked by the diode. Diodes cause a voltage drop of about 0.7 V.
    The ampere-rating of each diode should be equal or more than the alternator can deliver. That would be around 40 Amps in a 12 V system with a standard alternator.

    The diagram FJAfrica refers to, has a disadvantage. If your alternator has an internal voltage regulator the regulator is confused by the voltage drop caused by the diode. The battery voltage will be 0.7 V too low and not be fully charged.
    With an external regulator you can connect the +12V to the main battery. The regulator will compensate the 0.7 V voltage drop and keep your main battery fully charged.

    Ton
     
  9. hammerhead

    hammerhead

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    [quote author=MarkFJ40 link=board=1;threadid=7176;start=msg59900#msg59900 date=1068151417]
    I thought those parts store isolators got burnt up by winching ?
    [/quote]Yes and no. I have an extra ford starter relay for just that reason. At any time I can turn on a higher amperage connection to enable my rig to jump start itself or I can use it for winching. I also use it for jumpstarting others.
     
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