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hi need help with a dc charging issue

Discussion in 'General Electronics Discussion' started by davit, May 5, 2021.

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  1. davit

    davit

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    Aug 16, 2017
    i have a one amp draw on the 12v output but even if i disconnect this my R/H bank of batterys dont charge up as fully as the L / H side do, should my charging point be relocated , hope my diagram makes sense
    many thanks for looking
    davit pics062.jpg
     
  2. Bluejets

    Bluejets

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    Oct 5, 2014
    how do you know this.....??
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Due to the additional 12 V output the R/H side will be discharged more than the L/H side. So even after disconnecting the 12 V load it will take longer for the R/H side to get fully charged than for the L/H side.
    To verify: charge all four batteries fully (no loads attached). Then discharge using the 24 V port only (no current through the 21 V port. Then charge the 24 V setup as shown in your diagram, no loads attached.
     
  4. davit

    davit

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    Aug 16, 2017
    hi
    thanks for the reply
    after 2 days of 10amp charging volts on l/h bank are over 13v while the r/h bank show 12.4 , my 24v charger drops down to zero as though all batteries are fully charged, it takes another night of 12v charging on the r/h bank seperatly to bring them fully up to speed ,
    thanks
    davit
     
  5. davit

    davit

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    Aug 16, 2017
    hi thanks for your reply
    i actualy did as you sugested but as posted above the r/h bank are not fully charged, totally removed (0.5 amp 12v load.) to no avail.
    thanks
    davit
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Then your batteries may be faulty.
     
  7. davit

    davit

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    Aug 16, 2017
    they are differant sizes but new, and test ok , do you think it might help to move the positive 24v input to the top right battery where the output is, thanks again
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

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    I don't think that will help.
    What happens when you charge each battery individually?
     
  9. davit

    davit

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    Aug 16, 2017
    they all charge up ok individually, they are on my boat and spread around so as to help balance also access
    is tricky a central charge point is needed, thanks for your reply will try and dig out pics of boat setup
     
  10. Kiwi

    Kiwi

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    Jan 28, 2013
    Drawing current off the centre of a 24v battery bank is a recipe for disaster, unless there is a means to replace this current.
    Your R/H batteries will go flat, and the L/H batteries will be overcharged.

    First thing to do is remove all the batteries from the boat.
    Connect all four batteries in parallel to give 12v and then charge then up on a 12v charger.
    This will even out the battery charge across all the batteries.
    Then get the batteries tested.

    You need to change the connection points for the 12v output to the posts on the L/H batteries, not the R/H batteries.

    You then need to fit a battery charge equaliser.
    The Redarc CE10 is the one I normally use. Redarc is in Australia, so don't know if they are available where you are.
    10A Charge Equaliser | REDARC Electronics
    The CE10 will keep the centre tap voltage at half the battery voltage. If the alternator voltage is 27.6v, the centre tap will be 13.8v.
     
    Harald Kapp likes this.
  11. davit

    davit

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    Aug 16, 2017
    hi kiwi
    thanks for the reply
    and the link to redarc unfortunaly i cannot afford this item, what i can do is completely remove the 12v feed from the set up
    would this cure this charging issue ?? if needs must i could allways have a totally seperate 12v battery for any 12v draw that i might need, many thanks
    davit
     
  12. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Probably cheaper to use a 24 V to 12 V step down converter instead of an additional battery and charger.
     
    davit likes this.
  13. Kiwi

    Kiwi

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    Jan 28, 2013
    Yes, removing the 12v load will solve the battery charging imbalance.
    You still really need to hook all the batteries up as a 12v bank and charge them to even them out.

    I see you are in the UK, so you should be able to get a reasonably priced 24v-12v reducer for your 12v load.
    The electronics guys will call them "step down converters" but us in the automotive industry usually just call them reducers. Same thing, different name.
     
    davit likes this.
  14. davit

    davit

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    Aug 16, 2017
    thanks to kwwi and harald, you have both been really helpfull embaressed i did not think of using a reducer , have now got one
    on order, might be awhile before i can test it on the water, ( due to covid situation / restrictions ), will let you know i get on later,
    thank you both again what a wonderfull forum
    cheers
    davit
     
  15. Kiwi

    Kiwi

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    Jan 28, 2013
    No problems, glad to help.
     
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