A Question of Two Batteries

Discussion in 'Tech/Mech General' started by ian4apenny, Sep 8, 2016.

  1. ian4apenny

    ian4apenny Funster

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    Just changed motorhomes and being 'a bit of a scrooge', I removed the 2nd Leisure battery fitted to my former 2 year old motorhome with a view to using it on the new one. Trouble is, the "older" battery is rated at 100Ah and the battery on the new MH is rated at 90Ah. The batteries are also different makes- although they are both proper camping leisure batteries.
    Can anyone tell me how they should be connected and whether they need any fuses (or resistors) between them?
     
  2. scotjimland

    scotjimland Funster Life Member

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    If beside each other and connected in parallel with short cable, you don't need fuses...

    connect + pos to + pos and -neg to -neg

    For optimal performance they should be the same make, age and capacity.. in the real world, it doesn't matter too much ..



    [​IMG]
     
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  3. ian4apenny

    ian4apenny Funster

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    Absolutely excellent Scotjimland. My job for the weekend.
    Thanks Ian
     
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  4. Thursdays Child

    Thursdays Child Funster

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    Would I be right in thinking that both batteries, connected as above, would be recharged by a) the engine whilst on the move and b) by the charging unit when hooked up to the mains ?
    Also, when in use would both batteries be drained together or one after the other ?
    Thanks
     
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  5. scotjimland

    scotjimland Funster Life Member

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    a) yes,
    b) yes,

    and drained together
     
  6. Thursdays Child

    Thursdays Child Funster

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    Many thanks, Jim
     
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  7. pappajohn

    pappajohn Funster Life Member

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    Make and capacity don't matter.
    The charger will only see them as one 190ah battery.
    Age, on the other hand, does matter.
    If the older one is more than a couple of years old it may have a reduced capacity and will pull the better one down to a reduced capacity as it tries to bring the older back to full capacity when not on charge..
     
  8. ian4apenny

    ian4apenny Funster

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    Thanks TC for asking the other questions I should have asked and Scotjimland & Pappajohn for supplying the answers. The battery from my past MH is indeed no older than 2 years.
     
  9. Neilfg

    Neilfg Funster

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    For the charging to work at best they would both need to be the same type ie. Gel, AGM, or Lead Acid, also the control panel again depending on the make and features may need to be setup for the larger Ah.
     
  10. Thursdays Child

    Thursdays Child Funster

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    and thanks to pappajohn.
    We don't want the weight and "nuisance" of a generator or the expense of a roof mounted solar panel, so a second battery would seem to suit us best.
     
  11. pappajohn

    pappajohn Funster Life Member

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    Solar panel won't cost a lot more than a decent battery, but will be considerably lighter.
    Average 110ah battery may be 20+kg
     
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