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Lead Acid Battery Charger Help Request

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by jagzviruz, Dec 9, 2006.

  1. jagzviruz

    jagzviruz New Member

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    Hi people ..

    I am trying to make a Lead Acid Battery charger for a
    Sunca 6V 4.5Ah
    Can anyone help me with a schematic ? I would like to make it a dual purpose for a 12 V as well..I was wondering if a Bridge out put to LM317 to Output terminals will suffice to make a charger ??And yeah how should we conect the terminals for the charger ? I mean

    + of charger to + of battery or
    + of charger to - of Battery ?
     
  2. Hero999

    Hero999 Banned

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    If you really need to ask this then perhaps you don't have enough experiance to build this project.
     
  3. bizzareodave

    bizzareodave New Member

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    LOL!

    AAaaand, a single LM317 won't cut it...

    note: I'm agreeing heavily with Hero999
     
  4. dave

    Dave New Member

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  5. RODALCO

    RODALCO Well-Known Member

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    Get some experience first, and do some reading re chargers.
    Some of your suggestion re connecting the accu will be instant smoke or fire.

    Be safe and buy yourself a charger from the local shop with does the job instead of burning your house down.
     
  6. mvs sarma

    mvs sarma Well-Known Member

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    Last edited: Jul 7, 2008
  7. bizzareodave

    bizzareodave New Member

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    I don't know where you got that from, but I would recommend around 14V charge voltage for a 12V SLA, and the circuit you posted up before would take a bloody long time to charge a 4.5Ah SLA.

    As RODALCO suggested, just go buy one it will be cheaper and safer.


    But if you insist on making one yourself, take a look at the L296 from ST Microelectronics

    Code (text):
    http://www.st.com/stonline/products/literature/ds/1333/l296.htm
    It is a DC switching regulator up to 40V 4A output. Make sure you heat sink it well if you intend on using it...
     
  8. fever

    fever New Member

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  9. jagzviruz

    jagzviruz New Member

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    Thanks everyone for your advices .. have been busy over the past few days ... and thanks for advicng me to buy the charger .. but i plan upon makng the kit .. coz nothing beats the risk to burn the house down ..
     
    • Like Like x 1
  10. sam2

    sam2 New Member

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  11. bunghole

    bunghole New Member

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    mvs sarma,
    i looks at the diagram and want to know which side the battery links to, if its a "cycle use" charger and if you can use it to charge a 12v 18.0Ah lead acid battery and what kind of supply you need for it
    ,Thanks
     
  12. mvs sarma

    mvs sarma Well-Known Member

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    you have to supply DC to it as input at pins called '0' and '+'

    the output will be taken for charging at pins called '-' and '+' and these are on the right side of the image where you also find pin details of LM317.

    Initially you have to calculate the values for 13.8 volts and the current sense resistor value for the current you needed.

    Obviously +ve of bty is connected to +ve of charger output-- (this prevents any accidental wrong connection with all knowledge one has-- ref to post originators-doubt)
     
  13. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi jagviruz,
    Attached two versions of a sealed lead acid charger.
    By choosing the components shown, you can charge 6v or 12v batteries.

    The layout pcb is also shown, but the transformer tags shown may differ
    from yours, take care.

    Regards
    EricG
     
    Last edited: Jul 7, 2008
  14. mvs sarma

    mvs sarma Well-Known Member

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    Hi EricG,

    Perhaps the fuse F2 shold be after D2 and before the Battery +ve.

    It is not easy to adjust 13.8v output as with bty it will fall and without a demmy load (dMM) being the only load diode D2 drop cant not be measureable. thus it may be better to have a resistor of say 6.8K or 12K (depening on Bty,) so that the voltage can be set.

    Finally the circuit may not have short cct protection with bypass transistor.
     
    Last edited: Jan 16, 2007
  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi sarma,
    the fuse #2, is to protect you in the event if you ever short the output
    terminals with the battery connected. Shorting a sealed lead acid battery
    is not a good idea. They get very hot and vent electrolyte, blowing out
    the seals.

    I designed the charger to be a 'floating type' constant voltage charger, so
    the equipment that the charger/battery powers, can be connected all the
    time.[ set fthe output for 13.8v or 6.9v to suit your battery]

    You could add an extra fuse if you wish.

    Hope this helps

    Regards
    EricG
    I dont understand the question about the diode/resistor, please explain.
     
  16. mvs sarma

    mvs sarma Well-Known Member

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    Hi EricG,

    that if fine ,thanks
     
  17. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi sarma,
    the reason why I do not have a dummy load across the output is so that the
    battery is not slowly discharged, when the mains supply is not connected.
    Thats why the diode is also included, no discharge path thru the adjustment
    resistors.

    If you want to add current limiting, connect a low value, high wattage
    resistor in the emitter path of the power transistor. The 7812 will internally
    limit to about 1 amp.

    Regards
    EricG
     
  18. mvs sarma

    mvs sarma Well-Known Member

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    Hi, i mean to say that (without floating issue), if there is no load the output will be measured by DMM without the diode drop of say 0.7Volts. thus if we adjust 13.8V, by the time actual load is given the output will be less by 0.7 ie., 13.1 volts approx.

    whereas if you have a output bleeding resistor just after diode to neg comm, this issue will not arise.
    A 1 mA load may not matter I believe.
    Hope i am more clear now-- sorry for lack of vocabulary
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi sarma,
    you will find that with the battery connected that there will be sufficient residual current flowing into the battery via the diode that you will be able adjust the voltage ok.
    I have about 100+ laser systems using the charger setup, no problems in the past 10 years.

    Give it a try.
    Regards
    EricG
     

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