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BQ27441-G1: BQ27441 problem with 950 mAh LiPo battery

AlexHome
Intellectual 990 points
Part Number: BQ27441-G1
Other Parts Discussed in Thread: GPCCHEM, BQSTUDIO

Hello! I have an BQ27441-G1A and 1000mAh and 950mAh batteries (max charge voltage 4.2V).

So with default Design Capacity (1340mAh), Design Energy, Terminate Voltage, and Taper Rate the battery 1000 mAh worked for about 35 hours in some design. If replace it with 950 mAh, then the operation time is reduced to 22 hours. I tried to implement a flowchart from SLUUAP7 (changed typical values, to a 950mAh battery) : as before reconfiguration 1000 mAh battery works for about 35 hours, and 950 mAh - about 22 ... What could be the problem? The flowchart precisely configures the microchip (the checksum is updated).

  • 0
    TI__Genius 10370 points
    Alex,

    1) I am slighty confused when you say the operation time of 22hours and 35hours. The amount of run time is determined by the load applied. can you elaborate more on the issue?
    2) When you say you have a 100mAh and 950mAh battery why are you setting the design capacity 1340mAh?

    Thanks,
    Eric Vos
  • 0 in reply to Vos
    Intellectual 990 points
    Eric, thanks for answer!
    1) Applied load is approximatly 23-28mA in both cases (i.e. with 1000mAh and 950mAh batteries). We can assume that it is constant.
    2) 1340mAh - it is default design capacity of BQ27441-G1A (from the box). Those. When connecting 1000 mAh battery to BQ27441-G1A out of the box (without setting parameters), the operating time is 35 hours, and at 950 mAh only 22 under the same conditions. If the parameters are configured, the result is the same ...
  • 0 in reply to Vos
    Intellectual 990 points
    Eric, I apologize, I forgot to note that it is focused on the readings of the SOC register (state of charge).
  • 0 in reply to AlexHome
    TI__Guru* 76230 points
    Alex,
    Without properly configuring the gauge, which it doesn't seem like you are doing , the accuracy of the gauge will be off.

    Pls follow the instructions in the quick start guide for this device and that will get your units functional in no time.

    www.ti.com/.../sluuap7

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 990 points
    Hello, Onyx!

    Thanks! About configuring I wrote:
    //I tried to implement a flowchart from SLUUAP7 (changed typical values, to a 950mAh battery) : as before reconfiguration
    //1000 mAh battery works for about 35 hours, and 950 mAh - about 22

    So I can't understand why reconfiguring didn't work...
  • 0 in reply to AlexHome
    TI__Guru* 76230 points
    Alex,
    I really don't understand what the issue here is. Can you provide a bqstudio log of your experiment? Did you evaluate the gauge using gpcchem to determine if that cell profile is close to the default profile in the gauge. This ought to be the very first step you do before using this particular gauge. Can you pls do that and show the gpcchem reports

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 990 points
    Onyx, thanks! I do not use bqstudio but i'll try to follow SLVA725A (Simple Guide to Chemical ID Selection Tool (GPC)) to find nearest Chem ID. But will i able load this ID into BQ27441-G1A via I2C? I think no...
  • 0 in reply to AlexHome
    TI__Guru* 76230 points
    No You will not. You need bqstudio, that unfortunately is a requirement for configuring the gauge.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 990 points
    Onyx, thanks! I'll be searching fo BQ27GDK000EVM to use with bqstudio...
  • 0 in reply to Onyx Ahiakwo
    Intellectual 990 points
    Hello, Onyx!

    I found the BQ27GDK000EVM. I connected the battery in accordance with 6.9.2 Optional Configuration (i.e. I sealed the resistor and moved the jumpers). But there were questions:
    1. where to connect the TEC battery resistor? Closer to Pack + or Pack-
    2. Do I need to do something extra to get the data or is it enough to run the Auto Cycle GDK with a log entry?
    3. How to make it so that instead of Time Stamp it is written just Time (in seconds elapsed according to SLVA725A). Or, for analysis, will it be possible to download a csv file with a time stamp?
    4. How, after receiving the GPCCHEM_GPC_report.zip results, create the corresponding Golden file and how to flash it in bq27441 (I also successfully connected the chip to BQ27GDK000EVM and it saw the bqStudio)
    5. Is it possible to set Design Capacity in the Golden file and if so, how?
  • 0 in reply to AlexHome
    TI__Guru* 76230 points
    hi Alex
    1.The quickstart guide has instructions on setting up the EVM. Why aren't you following it?
    2.autocylcle gdk with log entry is sufficient.
    3 For analysis, elapsed time is what is needed and not time stamps.
    4. The instruction manual for gpcchem contains instructions on what to do with the files. You need program the chem id that came up as having the closest match to your cell using the chemistry tab of bqstudio.
    5. Yes, the quick start guide addresses this.
    www.ti.com/.../sluuap7

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 990 points
    Thanks Onyx! But I can't find chemisty tab for my bq27441... Where can I find this tab?
  • 0 in reply to AlexHome
    TI__Guru* 76230 points
    sorry,This gauge which you are using does not have that functionality to program the chem id that comes up as the closest match. Bqchem report will have details on how close the preprogrammed hardcoded ids are to your cell.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Intellectual 990 points

    ok, Onyx! Thanks anyway!

    But what about connection of 10k NTC resistor? I follow EVM user guide but there are two temperature/resistor connectors: J1 (for external temperature transistors) and J9 (with RID). And there are no information about connection of NTC resistor.

  • 0 in reply to AlexHome
    TI__Guru* 76230 points
    Hi Alex,
    The thermistor should be connected to the bin pin and the other end to ground. the guage uses the thermistor to know/detect that a battery has been inserted.
    thanks
    Onyx