batteries

Discussion in 'Tech/Mech General' started by big al 1, Jul 22, 2012.

  1. big al 1

    big al 1 Read Only Funster

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    can anyone tell me if i can use an 85 amp & a 110 amp together & would i need tto modify the charging system thnks
     
  2. Terry

    Terry Funster

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    Hi and welcome :thumb: YES and need to know what charger you have now ? In theory you have 200 amps ish so need around a 20 amp charger :thumb: but a 10 amp will do -just takes twice as long :Smile: and a 5 amp will take 4 x longer -
    terry
     
  3. pappajohn

    pappajohn Funster Life Member

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    Taken from a previous post by me...


    Quote:
    Originally Posted by loubsterlouise
    Well for a start I was led to believe that batteries only charged to the lesser or weaker one so why connect all 3 if 2 have larger capacities.I wouldn't know where 2get bits from or what bits required.Finally not very confident with electrics and with 2small kids wouldn't want to get it wrong.




    then you were lead to believe wrongly.....a myth.

    you can connect any sized battery to any other sized battery without problem.

    the only time it really matters is if one battery is beyond help.....or is a different type...gel, AGM etc.

    a simple example.

    take a sink basin, a washing up bowl and a large jug.

    basin = 125ah battery, bowl = 100ah battery and jug = 75ah battery.

    now stand the jug in the bowl and the bowl in the sink and start to fill the jug.

    once the jug is full the water will overflow into the bowl and in turn the bowl will overflow into the sink.

    all three are now full.

    same applies to batteries.

    once the 75ah is full it wont take any more charge but the charger will continue to charge the 100ah until that is full, then it will continue to charge the 125ah until that too is full.

    you will then have one large battery of 200ah capacity.

    the charger doesn't 'see' 3 batteries...only one 200ah battery.

    if one battery is faulty or old it will then impact on the total capacity...it wont take/hold a full charge but the two good ones will still be fully charged but will show an overall reduced capacity due to the duff battery..
     
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  4. Wildman

    Wildman Read Only Funster

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    how ever the self discharge of the duff battery will affect the other two as they try to equalise the voltage and hence the two good batteries whilst capeable of holding a full charge will not in most cases ever get there.
    Hence the advice to always buy a matched pair rather than adding a second battery to an existing one of unknown age or condition.
     
    Last edited: Jul 22, 2012
  5. pappajohn

    pappajohn Funster Life Member

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    think we need to agree to disagree Roger.
    i take your point when the bank is off charge, but not when being charged...the good batteries will still accept a full charge but will then be dragged down by the bad battery once off charge..


    quote....but will show an overall reduced capacity due to the duff battery..
     
  6. Terry

    Terry Funster

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    Easy way is to test battery's if one proves duff don't use it :BigGrin::thumb:
    terry
     
  7. DesRes

    DesRes Funster

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    It will be fine, don't fret, do it, your charging system will cope.:thumb:
     
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  8. haganap

    haganap Funster Life Member

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    interesting, last time I was given that advice I ended up with two kids :Eeek:
     
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  9. thesonya

    thesonya Read Only Funster

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    good, interesting
    [​IMG]
     
  10. PaulyP

    PaulyP Funster

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    What happens then - does the floor get wet !:Rofl1::Rofl1:
     
  11. Incamania

    Incamania Funster

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    Hi Big al 1
    This subject of charging 2 batteries from a single source crops up regularly and many knowledgeable replies have been posted, fortunately there is a simple non technical solution to the problem - purchase ,as I did, a 2 ACCUMULATOR CHARGER from www.kemo-electronica.eu . Their part number is M102N. If I remember correctly the unit costs about £15 and works well. I have 3 different capacity batteries which I recharge as required from output 2 whilst leaving my 90Ah leisure battery permanently connected to output 1.
    Connecting up the unit is straight forward as full instruction are supplied.
    The basic connection set up is source eg solar panel - panel regulator - M102N input - output 1 to one battery, output 2 to your other battery. You will only need to make up suitable connecting leads and site the unit which measures approx W84 H58 D33 mm.Don't forget in line fusing. Full instruction and cct diag are supplied. Delivery was quick.
    I don't have any connection with this company - just a satisfied user.:thumb:
    Hope this helps.
    Brian
     
  12. Reallyretired

    Reallyretired Funster

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    Thing is most motorhomes have their batteries in a bank i.e. connected together. The two output charger would only have a use if the two sets of batteries were connected to separate equipment on the output side, as I assume yours are. Most setups are not however, so this charger would not serve any purpose for most people.
     
  13. Wildman

    Wildman Read Only Funster

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    We don't disagree at all John, when on charge the good batteries will charge fully, I agree.
    when off charge the good batteries will discharge via the duff battery as the voltages equalise... you agree.
    No need to confuse people further.
     
  14. JJ

    JJ Funster

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    Well done DesRes... a one sentence, understandable post which speaks the truth (for almost all situations...)

    JJ :Cool:
     
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