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battery discharging circuit/ battery full charge detection

Discussion in 'Power Electronics' started by haneef, Mar 18, 2010.

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  1. haneef


    Mar 18, 2010
    Hello...I want to build a circuit for battery discharging...or even to detect a battery when it is fully charged.....can anyone please help me??
  2. neon


    Oct 21, 2006
    to discharge a battery all you need is a load. If you want to discharge it at a certain rate just put a power transistor across and vary the base. to detect a fully charge battery a comparator will do it or even a LED if designed carefully
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    It also depends on the battery type (a lot).

    Detecting discharge is usually based on voltage (but that voltage varies with load)

    Detecting a full charge is sometimes based on voltage alone, sometimes often there's a top-up charge applies after reaching a certain voltage. Other battery types a full charge is indicated by the rate of change of temperature, or even a small dip in the voltage.
  4. haneef


    Mar 18, 2010
    Hi der...thanx alot for your reply..actually i am a little weak in practicals..can you guys please tell me how to attach the load...i want to discharge the battery after it is fully charged or i want to connnect an led showing full charge...can you please show me the circuit..please...u can email it to me at [email protected]
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    A load is anything that you connect to the battery causing current to be drawn. It could be a lamp, a resistor, or some fancy electronics. Here is a simple example.

    To determine when the battery is fully discharged you need to know (at a minimum) what type of battery and what nominal voltage it has.

    To connect a LED showing full charge, well, that is a complex topic...
  6. GreenGiant


    Feb 9, 2012
    Not entirely correct, you can check a battery's true voltage while it is charging if the voltage reading comes directly from the tabs of the batteries

    This should yield the voltage of the battery, rather than a charge/discharge voltage, though you will sometimes get discrepancies when close to fully charged/discharged
  7. BobK


    Jan 5, 2010
    Plus the internal resistance times the charging current.

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