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BQ24193: Voltage measurement output

Frank White
Prodigy 30 points
Part Number: BQ24193
Other Parts Discussed in Thread: BQ27441EVM-G1A, EV2400

Is it possible to determine or read the battery voltage either by i2C or by altering the device settings and observing the status lines changing?  For my design, if the system is dormant for several months I want to discharge the battery to about 3.6V but do not have an analog input to my micro.

Thanks

  • 0
    TI__Expert 8230 points

    Hello Frank,

    The bq24193 doesn't have an integrated ADC.

    If the device is in the charging state, you could attempt to reduce the charge voltage limit and monitor the charging status register until it reports "Charging Done", but this would only work during charging. If charge's disable, the device charging status would just read "Not Charging". 

    If using the bq24193, the recommended method would be to use a fuel gauge to obtain voltage measurements over I2C using the MCU. Another option is using devices from the bq2589x family that do have an ADC that can measure VBAT.

  • 0 in reply to Fernando Lopez
    Prodigy 30 points

    Fernando, thanks for your response.  The system does have the BQ27441 gas gauge so we will get the voltage from that.  Yesterday I got the EV2400 USB to i2C interface and the BQ27441EVM-G1A but have hit a snag.  My system has a large Li-ion battery: 14400mAh capacity and 52000mWh energy.  In the dev tool GUI, I go to Parameter Q&A to configure the gauge but cannot enter these large values.  (Max capacity appears to be 8000, energy 32767).  Going to the Tech' guide sluuac9a.pdf, page 31 reveals the device limitations, however, what happens if our application programmers stuff values in excess of these into the registers?

    How is offset 10 (design capacity) different to offset 14 (default design capacity) - and why is there a limitation difference?

    Frank.

  • 0 in reply to Frank White
    TI__Guru* 76230 points

    Hi Frank

    I will recommend you use a different system side gauge like the bq27531. That allows more for a larger pack. Also, you can scale the current related parameters including the design capacity and current as described in the app note and this one pager.

    5037.how to guage high capacity packs.pdf

    thanks

    Onyx