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HuckleCat's avatar
HuckleCat
Explorer
Oct 01, 2017

Coach Battery Setup

I have a single 12V battery as a coach battery.
It was set up like this when I bought it. It is a 1975 model class A.
What is this thing pictured?

I need to replace or modify it. When plugged into shore power everything works and the battery charges. However, I think there is something the matter with it. The positive wire at the left gets hot and evidently has done so in the past as it is charred a bit. The positive wire to the left is connected to the battery, the one to the right right goes into the inverter / charger. Would like to have 2 - 6V batteries but not sure what the fused device is.
??? What's this ???
  • HuckleCat's avatar
    HuckleCat
    Explorer
    Oct 02, 2017
    MrWizard wrote:
    HuckleCat wrote:
    I have a single 12V battery as a coach battery.
    It was set up like this when I bought it. It is a 1975 model class A.
    What is this thing pictured?

    I need to replace or modify it. When plugged into shore power everything works and the battery charges. However, I think there is something the matter with it. The positive wire at the left gets hot and evidently has done so in the past as it is charred a bit. The positive wire to the left is connected to the battery, the one to the right right goes into the inverter / charger. Would like to have 2 - 6V batteries but not sure what the fused device is.
    ??? What's this ???


    the built in converter does NOT work ?

    but this wiring gets HOT when your battery charger is running from shore power ?

    assumng your charger leads are connected directly to the battery ?

    then these fuses lead to something using power ?

    PULL the fuses, find out what does not work with out the fuses

    1975 ? does your fridge have 12vdc run setting ?


    Built in converter / charger works - one wire on that assembly was getting hot when plugged to shore power - likely as you said from corrosion and such.

    With those fuses out everything works except the charging of the batteries.

    The charging lead runs into one side of that fuse block and then from the other side a lead goes to the battery.
  • MrWizard's avatar
    MrWizard
    Moderator
    Oct 02, 2017
    HuckleCat wrote:
    I have a single 12V battery as a coach battery.
    It was set up like this when I bought it. It is a 1975 model class A.
    What is this thing pictured?

    I need to replace or modify it. When plugged into shore power everything works and the battery charges. However, I think there is something the matter with it. The positive wire at the left gets hot and evidently has done so in the past as it is charred a bit. The positive wire to the left is connected to the battery, the one to the right right goes into the inverter / charger. Would like to have 2 - 6V batteries but not sure what the fused device is.
    ??? What's this ???


    the built in converter does NOT work ?

    but this wiring gets HOT when your battery charger is running from shore power ?

    assumng your charger leads are connected directly to the battery ?

    then these fuses lead to something using power ?

    PULL the fuses, find out what does not work with out the fuses

    1975 ? does your fridge have 12vdc run setting ?
  • DrewE's avatar
    DrewE
    Explorer II
    Oct 01, 2017
    For the proper fuse size, what's the gauge of the wire protected by the fuse and what's the expected load? Generally fuses are sized based on the wire size, unless the wire is upsized to minimize voltage drop, in which case it's more a reasonable size for the load.

    If it's 8 gauge or heavier wire, 40A is fine. It's probably okay for 10 gauge in this situation, too, though I'd be careful particularly if the wire is enclosed such that it can't dissipate heat too effectively. At any rate, a 40A fuse would provide the same level of protection as the existing fusing with the existing fuses.
  • HuckleCat's avatar
    HuckleCat
    Explorer
    Oct 01, 2017
    time2roll wrote:
    That fuse holder is shot.



    Sounds good, looks like I can replace this antique fuse holder. I cannot determine what amp needed as the old glass tube types may be incorrect. They were 20amp - so one 40 amp blade type would work safely?
    Thanks also Wizard and Drew. That black connector thing in the photo was my charger getting the battery charged since the other thing is disconnected.
  • DrewE's avatar
    DrewE
    Explorer II
    Oct 01, 2017
    If you're really wondering why the two fuses in parallel, I can only assume it's because they couldn't source a single fuse of a sufficiently high rating at the time. The construction could be replaced with a single fuse or DC circuit breaker (and that would not be a bad idea, especially as it seems to be in less than great condition).
  • MrWizard's avatar
    MrWizard
    Moderator
    Oct 01, 2017
    the 'black' thing is a power plug, connecting something in the RV

    the fuse holders at the bottom of the picture, are a 'set' of parallel fuses

    probably going from the charge converter to the battery

    unplug, unscrew and clean all those connections, clean the wire terminals, get new screws or clean those, rust/corrosion causes resistance, resistance where a battery is charging, creates heat,
    check your battery, take it to an auto parts store and have it tested
    a shorted cell, will create high current and lots of heat

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