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Compiler/BQ35100: BQ35100 - issue in reading Battery remaining capacity

suyodhana suyodhana
Prodigy 180 points

Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO, EV2400

Tool/software: TI C/C++ Compiler

Hi,

I am trying to monitor State of Health of Battery with a design capacity of 6500mAh. BQ35100 is used to monitor the voltage,current and battery remaining capacity. I am able to get the voltage correctly but unfortunately battery remaining capacity is always reading as 100% irrespective of  its usgae. Current reading are always shown as 0mA. Am i missing any thing in configuring the BQ35100 Battery Guage. I am trying to understand the issue in reading Battery remaining capacity and current readings using BQ35100.

Thanks,

Suyodhana

  • 0
    TI__Guru** 107275 points

    Hello Suyodhana,

    Are you using an EVM with EV2400 and bqStudio to pull the data? If you are using an embedded MCU can you outline the steps you take to pull the data from the gauge? What mode are you operating in (ACC, SOH, EOS)?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 180 points

    Hi Wyatt,

    Thanks for your response.

    I am using Embedded MCU to communicate with BQ35100. ACC mode is selected and battery is of lithium thionyl chloride (Li-SOCl2)

    Here are the steps followed up in communicating with Battery Guage:

    1. GE is made high 

    2. send GAUGE_START()

    3.after 2 seconds send GAUGE_Stop().

    4. Final Accumulated value is read by sending AccumulatedCapacity register address 0x02;

    Do i need to perform  any calibration after inserting a new battery? In order to get the current battery percentage for (Li-SOCl2)) battery, what could be the best operating mode selection. 

    Thanks,

    Suyodhana

  • 0 in reply to suyodhana suyodhana
    TI__Guru** 107275 points

    Hello Suyodhana,

    The BQ35100 doesn't track battery health information in ACC mode, it just collects passed charge information. You will need to set the gauge up in EOS mode to get some SOH data and EOS warning.

    Are you reading 4 bytes from the accumulated capacity register? If you are logging the data while current is flowing you should see some values using current(), do you have a log of the tests you have done?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 180 points

    Hi Wyatt,

    A big thanks for your inputs. Now i see some progress in the data that is being read from the battery guage bq35100. Following is the log for the configuration of BQ35100 in EOS mode.

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

    Battery Voltage 3527, Capacity 100, current 65490,tempe 29
    Battery Voltage 3527, Capacity 100, current 65489,tempe 29
    Battery Voltage 3527, Capacity 100, current 65490,tempe 29
    Battery Voltage 3527, Capacity 100, current 65489,tempe 29
    Battery Voltage 3527, Capacity 100, current 65490,tempe 29
    Battery Voltage 3527, Capacity 100, current 65490,tempe 29
    Battery Voltage 3527, Capacity 100, current 65489,tempe 29
    Battery Voltage 3527, Capacity 100, current 65490,tempe 29
    Battery Voltage 3527, Capacity 100, current 65490,tempe 29
    Battery Voltage 3527, Capacity 100, current 65490,tempe 29
    Battery Voltage 3528, Capacity 100, current 65490,tempe 29
    Battery Voltage 3528, Capacity 100, current 65490,tempe 29

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

    Battery parameters were being read for every 10 seconds. Battery Capacity still is showing it up as 100%. How ever i am able to see some data from the current register address. Temp 29 celsius is room temperature and its also matching.  Am i missing any thing in reading this parameters?

    Do i need to use new battery command even after a restart of the MCU ? Is it causing the battery capacity to remain in 100% at always.  When do we need to perform Battery Guage calibration. Could you please let me know your inputs on this.

    Thanks,

    Suyodhana   

  • 0 in reply to suyodhana suyodhana
    TI__Guru** 107275 points

    Hello Suyodhana,

    I'm glad you're getting it working now.

    For the gauge to report accurate EOS it must be programmed with a chem ID that matches the battery very closely, EOS mode is better at giving a warning for low battery life.

    You should only do a new battery command when you have inserted the new battery. You should before the calibration before the start of gauging, then the gauge should be good for it's lifetime if the DF remains valid.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 180 points

    Hi Wyatt,

    Good Evening,

    I have observed that Battery Percentage value is not being updated even after a continuous run of 8hr on the battery. Apart from 100% value I am unable to read any other value. The issue remains the same.  Am I missing anything in the configuration section.  

    I have gone through the data sheet in order to program the Device with Chem_Id. But I am unable to find any info on how to program the chem_id and how to perform the calibration using MCU interface. Is it possible to calibrate and program the Chem_id using the MCU interface. and if its possible could I get any procedure for it. Current Chem_id from the device is read as 0x0606. Battery being used is of lithium thionyl chloride (Li-SOCl2).

     

    Thanks,

    Suyodhana

  • 0 in reply to suyodhana suyodhana
    TI__Guru** 107275 points

    Hello Suyodhana,

    In order to report accurate SOH data the chem ID must match very closely in EOS mode, the main purpose of EOS is to use the long and short running averages to determine if the battery will be dead soon.

    You should program the gauge with the exact battery you are using to get accurate SOH data in EOS mode because the voltage is very flat for most of the LTC batteries life.

    You can look through this thread for more information: https://e2e.ti.com/support/power-management/f/196/t/840232

    The calibration information is in section 3.2 of the TRM, all the procedures can be carried out by the MCU. 

    Here is the TRM: https://www.ti.com/lit/ug/sluubh1c/sluubh1c.pdf?ts=1596466375056&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ35100

    Sincerely,

    Wyatt Keller