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BQ35100: some questions

R.Fukunaga
Expert 2525 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO, EV2400

Tool/software:

Hi all,

My customer would like to ask you some questions of BQ35100.

1) Parallel connection of batteries
I am thinking of connecting multiple batteries in parallel. Is there any problem?

2) Pull-up destination of ALERT pin
According to Figure12 in the datasheet, ALERT pin is connected to REG25 (2.5 V internal LDO output).
According to the specifications of ALERT pin in Pin Function, it is described as an open drain output.
If it is an open drain, I am thinking of using external power supply (REGIN input) as the pull-up destination. Is there any problem?

3) About calibration
According to the data sheet 8.2.2.1 Preparation for Gauging, it is read that calibration is required by an application called BQStudio.
I am assuming that the I2C connection destination is an embedded microcomputer. Do I need to install a separate connector to connect to the PC for calibration?

(4) About the external thermistor
You said you can choose between a temperature sensor built in the IC and an external thermistor.
An external thermistor is used to measure the exact temperature of the battery when the distance between the IC and the battery is far.
Is the temperature sensor built in the IC sufficient if the distance between the IC and the battery is close?

Best Regards,

Ryusuke

  • 0
    TI__Mastermind 27405 points

    Hello Ryusuke,

    This question has been assigned and will be reviewed when possible.

    Thank you,
    Alan

  • +1 in reply to Alan Frias
    TI__Mastermind 26875 points

    Hi,

    1) no issue

    2) this should be ok

    3) There is a calibration plug in available using BQstudio. If you want to use BQstudio you will need to also use an EV2400 as the "programming microcontroller". You will need an EV2400 to program a chemid on to the gauge is necessary. Calibration can be done by hand.

    4) For higher accuracy, we recommend using an external thermistor placed on the battery pack. It is difficult to say what level of error you will get if you use the internal thermistor far away from the battery.

    Regards,

    Diego

  • 0 in reply to Diego
    Expert 2525 points

    Hi Diego,

    Thank you for your reply.

    Do I need to calibrate every time I change the battery?

    There is no problem to calibrate when the device is shipped. But I think it is difficult to calibrate when the battery is changed on site. I can make a compromise if the specification is that calibrating increases the accuracy, but it is possible to detect the approximate remaining amount without calibrating.

    Best Regards,

    Ryusuke

  • 0 in reply to R.Fukunaga
    TI__Mastermind 26875 points

    Hi Ryusuke,

    No, swapping batteries should not require a recalibration to get accurate voltage, temperature, and current readings. Other parameters may need to be changed to match the battery characteristics being used. 

    Regards,

    Diego