Wiring spare battery?

Discussion in 'Motorhome Chat' started by Touchwood, Apr 6, 2014.

  1. Touchwood

    Touchwood Funster

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    I carry a spare habitation battery, but currently its not wired in parallel with the main habitation battery as they're different sizes and I understand that they would need to be the same to have them permanently connected.

    I wonder, however, what would happen if I wired them with a switch in the circuit so I could switch between them? I could then alternate them easily by flicking the switch. All advice welcome.
     
  2. Geo

    Geo Trader - Funster

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    It would work:thumb:
    But dont get totaly hung up on same size batterys
    Yes its good best practice

    example 100amp + 100 amp = 1 big 200amp battery

    example 100amp + 80 amp = 1 big 180 amp battery
    still better than your 100 amp single
    Charging might be slightly altered but no biggy in my opinion we will get the purist view though im sure
     
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  3. tonyidle

    tonyidle Funster

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    Agreed - I'd simply wire them in parallel.
     
  4. pappajohn

    pappajohn Funster Life Member

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    as Geo said........

    your charger and 12v system only see one large battery, not a myriad of different sized smaller ones.

    the only time it could be detrimental is if one battery is failing and has a lower capacity than it should have, then the better battery wont fully charge either as the combined voltage and amps will fool the charger into thinking the BIG battery is fully charged
     
  5. irnbru

    irnbru Funster Life Member

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    I had a mechanic do this to our MH last week. He attached a 115 to the existing 80. We aren't going away in the MH now until easter so cannot test till then but hopefully our heating will no longer fail.
     
  6. aba

    aba

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    The only time you may have a problem is if one of the batteries is a lead acid and the other one a gel battery.
    Although I don't quite understand why if they are both 12 volt.
     
  7. TheBig1

    TheBig1 Funster Life Member

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    gel batteries and lead acid need different charging regimes and one takes a higher initial voltage for longer then a maintenance charge to keep it topped up.
     
  8. irnbru

    irnbru Funster Life Member

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    Please, How can you tell if one is gel or not...?
     
  9. Geo

    Geo Trader - Funster

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    Ordinary Batteries have a water type electrolyte (Battery Acid) easy to spill and splash

    Gel Cell batteries contain a silica type gel that the battery electrolyte is suspended in, this thick wallpaper paste like material allows electrons to flow between plates but will not leak from the battery if the case is broken.

    If you are going to remove a battery top up lid, Wear protective goggles + Gloves and wash any skin with large amounts of water if splashed

    Batteries should:Doh: Are mostly clearly marked
    G
     
    Last edited: Apr 7, 2014
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