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BQ24401 Pulse Charging Method

Knighty
Intellectual 380 points
Other Parts Discussed in Thread: BQ24401, BQ2000T, BQ2000, BQ24400

Hi all,

I am working on 2 cells NICd charger. Can anyone share BQ24401 reference design or app. note to implement pulse charging?

Thanks,

PP.

  • 0
    TI__Guru**** 150650 points

    What do you mean by pulse charging?

    Here is an app note describing the function of this IC: http://focus.ti.com/lit/an/slua064b/slua064b.pdf

    This IC is a version of the bq2000T.  The bq2000T also supports charging of lithium cells.  There is an EVM available for the bq2000T: http://focus.ti.com/docs/toolsw/folders/print/dv2000ts1.html

  • 0 in reply to Chris Glaser
    Intellectual 380 points

    Hello Chris,

    I mean, feeding the charge current to the battery in pulses. Understand that this method can reduce unwanted chemical reaction at the electrode surface. Not  sure BQ2000T can do this.

  • 0 in reply to Knighty
    TI__Guru**** 150650 points

    I haven't heard of using pulse charging for nickel cells.  It is common to use for lead acid cells in float mode.  As you noted, giving lead acid cells pulses of higher currents instead of a lower DC current can lengthen the cell's life.

    For nickel cells, detecting termination requires a constant current source to be applied to the pack and then looking at either the pack voltage or pack temperature to detect termination.  Applying a variable current will result in possibly missing the termination point and over charging the cells.

    The bq2000 and bq24400 do pulse the battery in both top-off and trickle charge modes.  This is explained in the datasheet on page 8: "During top-off, current is delivered to the battery in pulses that occur each second.  The fixed pulse width allows an average current of 1/16 of the fast charge current to be delivered to the battery every second."