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[No part number yet] Looking for recommendation for charging a two cell (7.4V nominal) Lithium-ion battery over USB.

Todd Skinner
Prodigy 50 points
Other Parts Discussed in Thread: BQ2057T, BQ24618, BQ24133

Hi,

I am looking into a battery charger IC for a 7.4V, 2.4Ah battery that I would like to charge over USB.  I believe a dedicated USB wall charger can supply 1-2 Amps, so a 2Amp max supply should be sufficient.  The product will have a long production life, but low volume (~200 per year) so a newer product that might be around for awhile would be ideal.

I identified two possible ICs:

BQ2057T

BQ24618 - USB friendly, I am not sure if I need this or not.

Any suggestions or advice would be appreciated.

Todd

  • 0
    TI__Expert 3160 points
    Todd,

    Can you clarify that you mean only to charge via a USB cable and wall charger so there is no need to properly meet charging requirements via actual USB port? You can also check the bq24133 as a simple stand-alone charger.

    You will of course also need a buck converter to raise the voltage up high enough to charge a 2S battery.

    Thanks,
    Rachel
  • 0 in reply to Rachel Moore
    Prodigy 50 points
    Rachel,

    It would primarily be charged via USB wall charger, but the customer could use an actual USB port on a computer if desired. The charging time would increase significantly, but the customer would like this option. Thank you for the recommendation on the BQ24133.

    Thanks,
    Todd
  • 0 in reply to Rachel Moore
    TI__Guru**** 165886 points
    I think Rachel meant to say "you will of course also need a BOOST converter....".
  • 0 in reply to Jeff F
    TI__Expert 3160 points
    Todd,

    While it is possible to charge 2S batteries from an actual USB port, it's not as straight forward as from a 5V wall adapter. Please make sure to take the time to consider all the input current limitations and what is needed to be USB complaint.

    Thanks for the correction Jeff. :)

    Thanks,
    Rachel
  • 0 in reply to Rachel Moore
    Prodigy 50 points
    Rachel,

    I currently use an FTDI chip in my application for UART to USB communication. FTDI has a good application note (AN_175) on how to use the FT-X series to detect if a dedicated charging port or a USB Host is connected. I will use the FT-230X, BQ24133 (with a boost converter) as a starting point and go from there. Thanks for pointing me in the right direction.

    Thanks,
    Todd