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BQ40Z50-R1: Companion parts for BQ40Z50-R1 for USB charge

Paul Beam74
Prodigy 20 points
Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQ40Z50, BQ27Z561-R1, BQ25895

I have a 1S4P 10 A-Hr Li-ion battery pack composed of 18650 cells that I want to charge via USB (or other external adapter).  What companion parts should I be looking at to be compliant with USB charging specifications and be stand alone?  When the battery pack is plugged in to my instrument, the I2C on the BQ40Z50 can be used as a fuel gauge, but it may be charged by itself where there is no host to program or monitor registers.  Ultimately, what I am looking for is the functionality of a standard USB battery pack where you put 5V in to charge, and you get 5V out.  

  • 0
    TI__Mastermind 24870 points

    Hello Paul,

    I'm moving this to the chargers forum.

    For the 1S4P pack, I suggest you look at some of our single cell gas gauges, mainly the bq27z561-R1. The bq40z50-Rx is too much for just a single cell pack.

  • 0 in reply to Kang Kang
    Prodigy 20 points

    OK.  I misunderstood.  Since I had multiple cells in parallel, I thought the z50 was the appropriate part -- it was also suggested by the battery vendor.

    If I use a fuel gauge with a charge controller like the bq25895, what do I do with the thermistor as it is either consumed by the fuel gauge or I believe the z561 has it internal?  Do I just mark the charger happy and depend upon the z561 to protect the cell?

  • 0 in reply to Paul Beam74
    TI__Guru**** 166546 points

    Paul,

    The charger and gauge bias the thermistor differently so you have to choose one or the other.  Most customers choose to connect the thermistor to the gauge and then use matched resistor divider from VREG to TS to GND to "make the charger happy".

    Regards,

    Jeff