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Thread: To isolate or to hard wire together??

  1. #1
    OLC Member binrat's Avatar
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    Default To isolate or to hard wire together??

    My truck is a 2012 Sierra 1500 with a 5.3 engine if that matters. Soon to have power into the back piggyback off of the trailer harness. The battery is going south bit by bit without me so its time. I have a second tray in the truck (it came that way) and have had the cables maybe since 2012. Just need to get the batteries which I think are going to be Crappy tire AGM battery.
    I have had other trucks which I did the dual battery setup which was just hardwired together with no isolation and have had no problems. But, I've been reading where that is pretty well an obsolete way.
    If I did go with some sort of separation, it would be a started solenoid from a Ford and a trigger wire off of the fuse panel.

    Thoughts on the way you would do it.

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    Do NOT want the starter solenoid from Ford.

    I know first hand that will not last as the solenoid is not rated for continuous use.

    You do want a continuous use rated solenoid from your favorite parts store. I have had one hooked up for the camper battery and that has lasted 11 years. The ford starter solenoid I first set up didn't last a week...

  3. #3
    OLC Member binrat's Avatar
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    Good point, just may keep it simple and hard wire the 2 batteries together.

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    OLC Member klahanie's Avatar
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    I'd probably want some kind of isolation, especially if supplying something that might draw power continuously (like a fridge or standby radio) or using dissimilar or different aged batteries. If using a plug end into the trailer harness socket then there's a disconnect right there - just in case. Last truck I simple used a solenoid - that was before the internet told us we need an expensive switch/management system ! Might have been a battery solenoid vs starter, idk, regardless it worked just fine. Agreed on the continuous rating, you can also get latching solenoid - they might last longer. And/or you could make a jumper for the 2 line terminals, just in case.

    As you probably know if the battery charge wire is small gauge you may not get much juice into the 2nd battery, but no harm in trying if you already posses a cable.

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    OLC Member uriedog's Avatar
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    I really like the continuous duty solenoid, and #2 or 2/0 AWG for the connection. #10 will take a long time to put a charge back in the batteries.

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    #10

    That's all I'm running to charge the two 12v camper batteries. (at the back of a 10 foot adventurer)

    Actually, that's all the camper has for inside wiring as a connection from the truck to batteries. (came from the factory that way...)

    What I would need to check is voltage in the camper and at the battery to see what the loss is and what the truck alternator would supply to the camper batteries.
    I know I checked it once before and there was no issue. It was 14+ volts...

    End of march, camper is all sealed up for the winter...

  7. #7
    OLC Member ssrig55's Avatar
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    My input is DO NOT USE A CHEAP SOLENOID! I have tried several types and lo and behold one has caught fire and burned up!!
    The worse types are the silver ones with threaded posts, they burn real good and if while it is burning is near another flammable item will get that going too.

    I was lucky as I was right there when it went up so managed to dump an extinguisher on it before my backhoe burnt to the ground.

    The other was a unit made for the job but had been re called because of......................yes...fire!

    Got rid of it and went out and purchased a battery to battery charger that has all the proper features, ie, 3 phases of charging etc.
    maybe the motto is to not scrimp on this item. This is what I use.


    web site for it:
    http://sterling-power.com/collection...ers-waterproof
    Very easy to connect.

    IF you are wiring it fresh I would go pretty big wire if the charge time is short and the alternator can handle it, otherwise most vehicles I have seen really have thin gauge that is not very efficient, particularly getting the battery up to a float faze of charging. Most systems get a charge back into the battery but the life of the battery is reduced when it does not get the charge it needs.

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    OLC Member klahanie's Avatar
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    Reread the OP, think I misunderstood. If the idea is to retro fit to the oem 2 batt underhood set up then yes I'd be sorely temped to simply hardwire with an oem parallel cable (my ford diesel was 2ga (?) given that a similar set up had been sufficient in previous vehicles, as stated in the OP.

    Of course it depends on what the second battery is wanted for. And I still like the idea of the provision for separation, if only for peace of mind when leaving the vehicle unattended as a flat battery is something we worry about. We use a manual battery selector switch. Here are two more automatic options fwiw:
    http://www.amazon.com/Cole-Hersee-48.../dp/B00LMGPHW2

    http://www.defender.com/product.jsp?path=-1|328|2290051|2290060&id=1508894

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    Quote Originally Posted by klahanie View Post
    Reread the OP, think I misunderstood. If the idea is to retro fit to the oem 2 batt underhood set up then yes I'd be sorely temped to simply hardwire with an oem parallel cable (my ford diesel was 2ga (?) given that a similar set up had been sufficient in previous vehicles, as stated in the OP.

    Of course it depends on what the second battery is wanted for. And I still like the idea of the provision for separation, if only for peace of mind when leaving the vehicle unattended as a flat battery is something we worry about. We use a manual battery selector switch. Here are two more automatic options fwiw:
    http://www.amazon.com/Cole-Hersee-48.../dp/B00LMGPHW2


    http://www.defender.com/product.jsp?path=-1|328|2290051|2290060&id=1508894

    @ Klahanie
    Just for giggles check the resistance between the two negative battery posts on your Ford diesel.
    Buddy's truck was reading 32 ohms....
    Explained why things weren't running right. Drivers side battery was only getting 10.5V charge as a result and the drivers side battery is what runs everything.

    Ford decided to terminate the negative ground wires to two different locations (separate frame rails)

  10. #10
    OLC Member binrat's Avatar
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    Quote Originally Posted by klahanie View Post
    Reread the OP, think I misunderstood. If the idea is to retro fit to the oem 2 batt underhood set up then yes I'd be sorely temped to simply hardwire with an oem parallel cable (my ford diesel was 2ga (?) given that a similar set up had been sufficient in previous vehicles, as stated in the OP.

    Of course it depends on what the second battery is wanted for. And I still like the idea of the provision for separation, if only for peace of mind when leaving the vehicle unattended as a flat battery is something we worry about. We use a manual battery selector switch. Here are two more automatic options fwiw:
    http://www.amazon.com/Cole-Hersee-48.../dp/B00LMGPHW2

    http://www.defender.com/product.jsp?path=-1|328|2290051|2290060&id=1508894
    Yes, dual batteries under the hood for more capacity.
    I've been thinking (god help me) about installing a simple marine battery disconnect switch for times when I want separation.

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