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BQ27426: BQ27426

Katsuhiro Kanao
Intellectual 1710 points
Part Number: BQ27426
Other Parts Discussed in Thread: BQ24726, , BQSTUDIO, BQ25601

HI

* Data flash

Does bq24726 have a function to store the battery profile that are measured by Dallas ?

If it is, does these stored in OTP or Ram memory ?

If it is , which manual should we read for operation.

 

 

State of Health

Is this parameter to know the battery aging. ?

How to define（QMAX and Ra） ? ex 50% is half of capacity from new one. ?

best regards K.Kanao

  • 0
    TI__Intellectual 1840 points
    Hello,

    The bq27426 is a rom-based gauge and you'll need to use one of the 3 default chemistry IDs.

    And yes, the state of health correlates to aging of the cell. After selecting one of the 3 chemistry ID, you'll need to perform a successful learning for the Qmax and resistance tables to be learned. Here is a document showing how to do it:

    www.ti.com/.../slua903.pdf
  • 0 in reply to Nabil M
    TI__Intellectual 1710 points
    Hi
    Would you please reply bellows ?

    1.Learning cycle
    *Cycle count
    My understanding is bq247426 has not flash memory, so it is necessary learning cycle at first to get update battery cell profile.
    How many cycle is recommend to make accurate.
    “Charge => Discharge”, one cycle is enough ?
    *Mass production.
    For mass production, is it OK to get RAM data from learned battery pack then write another battery pack the ram data to skip
    Leaning cycle ?
    *Which data to store and write ?

    2. GG accuracy
    *How much of accuracy is bq27426.
    In case of bq275200, this is described 1% of SOC. How about bq27426 ?

    3, State of Health
    *Would you please let me know how to calculate ?
    *Is there any manual to describe it or data about charging cycle vs State of Health ?
    * SOH LoadI which is factory programmed (default =–400 mA)
    How to change this values, which register is assigned ?

    best regards K.Kanao
  • 0 in reply to Katsuhiro Kanao
    TI__Guru* 76230 points
    Hi K. Kanao
    I would recommend you review the quick start guide in the link below. it addresses most of your questions.
    www.ti.com/.../sluubn3

    1. You need to first perform a chem id identification using gpc chem to determine if the hard coded chem ids in the bq27426 are a good match for your battery. if they do not show up as a good match then you cannot use the bq27426. If it is a good match, then you can run a learning cycle, just like the typical learning cycle process, where you discharge to empty, rest 5 hours, charge to full, rest 2 hours and then discharge to empty again and rest 5 hours.
    After the learning has been performed on one unit, you can extract a gmfs file which will be programmed on multiple units. The quick start guide lists out the process of what and how to store what in non volatile memory of your host

    2. You can get up to 5% error in accuracy. Could get better performance if the chem id is a perfect match.
    3. SOH load I should be a parameter in data flash which you can modify. I do not believe it is private but if it is you will have to reach out to us to via email open it up. State of health is calculated as FCC(SOHloadI, 25C)/design capacity.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    TI__Intellectual 1710 points
    Hi Onyx

    Thank you for your support.

    4.How to set "full and empty battery conditions"
    In page 3 of sluubn3(Quick-Start Guide) " Additionally, full and empty battery conditions must be set to match the system requirement"
    is described.
    This seems not mandatory.
    *What condition, these should be set.
    *How to set these for which registers ?

    best regards K.Kanaoa
  • 0 in reply to Katsuhiro Kanao
    TI__Guru* 76230 points
    terminate voltage will determine when the gauge reports empty. Charging voltage of the charger and the taper rate will determine when the gauge reports full like in all our other gauges.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    TI__Intellectual 1710 points
    Hi

    Thank you for your support.

    1. State of Health
    According to your answer. State of health is FCC(SOHloadI, 25C)/design capacity .
    Is the design capacity is QMax or initial parameter of Battery cell ?

    2. To detect Remained capacity = 100mAH
    Customer want to detect it by using SOC1 or SOCF.
    But these are % not mAH.
    Is it possible to detect it by changing % values and SOH ?
    Ex
    At SOH=100%, by setting SOC1 Threshold = 10% => Could detect at RM=100mA
    At SOH=50%, by setting SOC1 Threshold = 20% => Could detect at RM=100mA


    3.Golden file
    After learning cycle, customer would get the updated Rmax and Qmax by bqstudio of golden file.
    Is it right procedure for customer to write learning result to another IC by golden file with I2C command ?
    Does this data include chemistry setting data (4.2V, or 4.35V etc) ,too ?

    4. Chemistry setting by manual control panel of bqstudio ?
    Would you please let me know how to set ?

    best regards K.Kanao
  • 0 in reply to Katsuhiro Kanao
    TI__Guru* 76230 points
    Hi K.Kanao
    1. Initial parameter of the cell, i.e design capacity which you programmed on the gauge.
    2. This is SOC% not SOH. So those are set based on the gauge SOC.
    3.Yes, you extract a gmfs file and program other units. The gmfs contains your data memory parameters
    4. You can change chem ids except the to the default ones on the gauge. Pls see TRM for further details.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    TI__Intellectual 1710 points

    Hi Onyx

    Thank you for your support.

    I ask No4 question, again.

    My question is how to change from code(I2C) to inputs of manual control inputs of bq-studio.

    In bq-studio, manual command is required to input “ Enter Cmd”, “Access Style”, “Read Addr” and “length” as bellow  

    Otherwise, here are code examples. Would you please let me know how to convert these to manual input command of bq-studio

    Rd 0x00  0x08 0x00  (To read Chem ID)

    wr  0x00  0x32 0x00 (To write CHEM_C)

    rd  0x06 (To read Flag)

    best regards K.Kanao

  • 0 in reply to Katsuhiro Kanao
    TI__Guru* 76230 points

    HI K.Kano

    See snippets of how to use advance command to read a sub command and also to read a paramter like voltage. Although this was done on the bq27520

    , the process is similar.

    voltage reading.

    Note that commands and results are little endian.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    TI__Intellectual 1710 points
    Hi
    Thank you for your support.
    When using TI’s charger IC bq25601 with bq27426.
    Both IC need thermistors each other , but want to reduce to one..
    Do you have any idea or schematic to combine to one ?

    best regards K.Kanao
  • 0 in reply to Katsuhiro Kanao
    TI__Guru* 76230 points
    Hi Kanao,
    Your host will have to write the temperature to the gauge or you use the internal temp sensor of the gauge. No way to combine both.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    TI__Intellectual 1710 points

    Hi

    Thank you for your supoort.

    When GG use intetornal temp sensor or  to get temp data from Host wihout external thermistor.

    Is it not necessary to connect BIN pin to Thermistor ?

    Bin is used to detect battery cell.

    best regards K.Kanao

  • 0 in reply to Katsuhiro Kanao
    TI__Guru* 76230 points
    you can use a 10k resistor for bat insert detection or your host can inform the gauge when a battery is inserted. See TRM for additional details on bat insertion.
    thanks
    Onyx