• State TI Thinks Resolved
  • Locked Locked
  • Replies 10 replies
  • Answers 5 answers
  • Subscribers 65 subscribers
  • Views 548 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ35100: Fuel Gauge IC for Primary Cell Monitoring

Deepesh Chari
Prodigy 40 points
Part Number: BQ35100

Tool/software:

I am currently developing a humidity sensor-based wireless sensor node powered by a primary battery, either lithium thionyl chloride (LiSOCl₂) or lithium manganese dioxide (LiMnO₂). The objective is to operate the sensor for 5 to 10 years without battery replacement. To monitor the remaining battery life, I plan to integrate a fuel gauge IC.

The sensor operates for 20 µs during each measurement cycle and remains in sleep mode for the rest of the time. The measurement interval can be 5, 10, or 15 minutes. Currently, the active current of the sensor module is 20 mA, and the sleep current is 60 µA.

I am considering using the BQ35100 for fuel gauging.

Query: Can the BQ35100 be put into sleep mode during the sensor's sleep period to reduce average current consumption? Will doing so affect the accuracy of the fuel gauge’s readings or its ability to track the battery’s capacity over time?

Additionally, could you recommend other fuel gauge ICs compatible with both lithium thionyl chloride (LiSOCl₂) and lithium manganese dioxide (LiMnO₂) batteries?

Thank you for your assistance.

  • 0
    TI__Mastermind 26255 points

    Hi,

    The BQ35100 is the only gauge that can estimate capacity for non-rechargeable cells. 

    For lithium thionyl chloride (LiSOCl₂), you will need to use EOS mode.

    For lithium manganese dioxide (LiMnO₂), you will need to use SOH mode.

    Chapter 5 in the TRM describes the modes. bq35100 Technical Reference Manual (Rev. C)

    Chapter 6.1 describes the GE pin and how to reduce current consumption. 

    Regards,

    Diego

  • 0 in reply to Diego
    Prodigy 40 points

    So, does putting the device in sleep mode during the intervals affect the measurement reading?

  • 0 in reply to Deepesh Chari
    TI__Mastermind 26255 points

    Hi,

    The device does not take measurements when the GE pin is not enabled.

    Regards,

    Diego

  • 0 in reply to Diego
    Prodigy 40 points

    Subject: Clarification on EOS Mode Usage for Li-SOCl₂ Battery with BQ35100

    Dear TI E2E Support,

    If I am using a lithium thionyl chloride (Li-SOCl₂) battery in my application and intend to utilize the BQ35100 fuel gauge IC. Based on the datasheet, the End-of-Service (EOS) mode employs voltage, current, and temperature data to estimate the battery's internal resistance and its rate of change, which are indicative of the battery's remaining service life.

    Queries:

    1. Does the EOS mode rely on coulomb counting for capacity estimation?
      Based on the information provided, it appears that EOS mode does not use coulomb counting.

    2. Since I am using a Li-SOCl₂ battery, is it correct to use only EOS mode and not the Accumulator (ACC) or State-of-Health (SOH) modes?

    3. Will i be able to see the battery remaining (in percentage) or State of Charge (SOC) in EOS mode?

    Thank you for your assistance.

  • 0 in reply to Deepesh Chari
    TI__Mastermind 26255 points

    Hi,

    1) EOS mode does not utilize CC.

    2) Correct

    3) Yes, EOS will output an SOH value, 5.3.3 in the TRM describes this.

    Chapter 5 in the TRM describes the different modes.  bq35100 Technical Reference Manual (Rev. C)

    Regards,

    Diego

  • 0 in reply to Diego
    Prodigy 40 points

    Hi,

    SOH and SOC are two different quantities, right?

    Queries:

    1. Can we estimate the remaining battery percentage using SOH? If SOH is available in EOS mode, why is a separate SOH algorithm provided for Li-MnO₂ chemistry?
    2. Is there any documentation that shows battery capacity as a percentage in EOS mode?
    3. Since EOS mode doesn’t use coulomb counting, does putting the device into sleep mode between measurements affect SOC accuracy—unlike coulomb counting, which must always remain active? My intention is to reduce the average current consumption of fuel gauge IC.

    4. What is ACCUMULATOR mode? Does it use Coulomb Counting? For what purpose is it used for?
  • 0 in reply to Deepesh Chari
    TI__Mastermind 26395 points

    Hello Deepesh,

    We will continue to work on your question, today is a national holiday, Memorial Day.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    TI__Mastermind 26255 points

    Hi,

    Deepesh Chari said:
    SOH and SOC are two different quantities, right?

    Not in this case since these are for no rechargable batteries.

    1) for this device SOC = SOH

    2) SOH/SOC will be a percentage.=

    3) When in EOS mode, a GAUGE_START() command should be issued prior to any major discharge activity. This will ensure that any major discharge pulses are used in the determination of the battery's condition.

    4) Accumulator mode is used for nonchargeable batteries that are not  Lithium Manganese Dioxide (LiMnO2 ) or Lithium Thionyl Chloride (LiSOCl2 ).

    Regards,

    Diego

  • 0 in reply to Diego
    Prodigy 40 points

    Subject: BQ35100 Fuel Gauge IC pinout query

    Hi,

    I have a question regarding connecting a sensor to the BQ35100 fuel gauge IC.
    According to the pinout provided in the datasheet, i assume that the sensor should be connected between the BAT+ and PACK- pins

    Queries:

    1. Should I connect the positive terminal of the sensor to BAT+ and the sensor ground terminal to PACK-?
    2. Should the sense resistor be placed between the negative terminal of the battery and the GND of the sensor?
    3. What is the purpose of the VIN pin? Can it be left floating?
    4. As per the typical application circuit, the sense resistor value is 100 mΩ. Is it possible to change this value?
    5. Is it necessary to use a 10k NTC at the TS pin? If I don’t want to use it, should I pull the TS pin down using a 10k resistor? Does it have internal temperature sensor as an alternate option?
    6. Should I connect the REGIN pin to the BAT+ terminal?
    7. What is the purpose of the circuit marked in the blue box? Can the capacitors in that circuit be marked as DNP, and the resistors replaced with shorts?
    8. Can the SRP and SRN pins be interchanged?
    9. Why is the ALERT pin pulled up to 2.5 V? Can it be pulled up to the battery voltage instead?
    10. The datasheet recommends connecting the NC pin to VSS. Can it be left floating?

     Thankyou

  • 0 in reply to Deepesh Chari
    TI__Mastermind 26255 points

    Hi,

    1) BAT- and Pack-, please follow the EVM schematic bq35100EVM-795 Evaluation Module User’s Guide

    2) BAT- and Pack-

    3) Optional voltage measurement input, I recommend gnding unused pins.

    4) yes, you can choose a sense resistor of your choice for different current applications. What is most important is that you don't violate the SRN/SRP +/- 0.125V

    5) You can gnd this pin if it is unused, there is an internal sense resistor that can be used. However, it should be noted for the most accurate gauging the thermistor should be placed on the battery pack.

    6) Yes, as long as it does not violate abs max for that pin.

    7) that is a filter circuit for the sense resistor, these components are required.

    8) no

    9) probably not but it depends on the bat voltage.

    10) please gnd this pin.

    Regards,

    Diego