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6 to 10 cell NiMh charger needed

Giampiero Corsi
Prodigy 10 points
Other Parts Discussed in Thread: BQ24400, BQ2002, TPS3808, BQ2000, BQ2004

Can you suggest me an i.c. to charge battery pack of 6 or 10 cell NiMh (1.2V 2500mA/h) at about 1A, with detector of battery discharged (an output that sense the low voltage of battery to switch off the device). This device work only-one (without  a microprocessor), it is preferred few external components and a little case. Thank you

  • 0
    TI__Guru**** 150930 points

    Thank you for using TI and welcome to the e2e forums.  First, let me ask you to use a more descriptive post title.  We have hundreds of battery chargers, so you'll need to put some more detail in your title to help others see what type you need.  I have edited your title to be more appropriate to your question.

    Some basic nickel chargers are the bq24400/1 and the bq2002.  The input voltage and cell count you have will dictate which IC is better suited to your application.

    I'm not sure what the low battery feature that you desire is.  These chargers safely charge nickel cells.  If the cell voltage is too low, they start with trickle charge.  If you want a separate circuit to notify you when the battery is too low, a voltage supervisor is your best bet.  ICs like the TPS3808 work well here.

    Finally, you might want to use a higher charge current to accurately sense when fast charge should end.  You can talk with your battery manufacturer about what they recommend, but generally a charge rate of at least C/3 is needed for nickel cells.  I would recommend more like C/2 or C.  With 1 A and a 2.5 Ahr pack, you have 0.4C.

  • 0
    TI__Mastermind 31120 points

    TI has the bq2000 and bq2004 Nickel Chargers, but they are 7V processes and require many external components for the device to work.  TI does not have any small area designs for nickel chargers, but we have an extensive line of Li-Ion chargers which is the battery of choice for most applications because of their high energy density and ease of charging (partial or full charge).

    Nickel chargers have to maintain a constant curernt (CC) charge, at C/3 or greater, until the battery is full and rises in temperature (drops in impedance) to detect a full cell, which typically eliminates use of a USB source.

    Li-Ion cells charge at CC-CV (constant current-constant voltage) and the current tapers as the battery becomes full.  A lower CC is fine since the current will eventually taper anyway, thus most any source can be used to charge a Li-Ion cell.