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BQ24725A: must laptop battery initiate broadcast charging information to the charger?

Ras Sharif50
Genius 3455 points
Part Number: BQ24725A
Other Parts Discussed in Thread: BQ24133

dear All,

i am studying a smbus system containing a mcu ( as host ), a smbus charger, and a laptop battery ( smart/has smbus ).

i can read information of the smart battery; voltage, current, charger, and ...

i expect the battery initiate the communication and broadcast charging information to the charger and host.

but the smart battery doesn't broadcast any information.

i tested this system with and without the host.

Best Regards, Ras

  • 0
    TI__Genius 11850 points
    Hi Ras,

    How are you reading the battery information?

    The BQ24725A communicates with the host controller or smart battery through the SDA and SCL lines. Can you probe SDA and SCL to see if there's any activity there?

    Also, do you have an EVM + EV2300 that you can try? If the BQ24725A can communicate with a host, but not with the smart battery, then the communication problem is probably on the battery end.

    Best regards,
    Angelo
  • 0 in reply to Angelo Zhang87
    Genius 3455 points

    Hi Angelo,
    thank you for the reply.
    reading of battery information is through SMBUS. host ( MCU ) commands the battery to read the information ( state of the charge, voltage, ... ). the battery sends requested information to the MCU. i can see the data in debug mode ( micro controller develop environment ).
    also there is an digital analyzer which shows logic communication ( SCL and SDA ).
    there is no access to any EVM and other tools.

    i expected the battery ( a laptop smart battery ) to initiate broadcasting charging information to the charger ( BQ24725A ) with and without the presence of MCU. but it doesn't happen.

    is there a laptop ( smart ) battery which doesn't have broadcasting function? if the answer is yes, so how is it charged?

    Best Regards,
    Ras

  • 0 in reply to Ras Sharif50
    TI__Genius 11850 points
    Hi Ras,

    So your battery can communicate with the host through SMBus, but the battery can't communicate with the charger even though there is communication over the SDA and SCL lines?

    Is the charger able to communicate with the host? And just to be clear, we're discussing the BQ24725A, not the BQ24133, correct?

    Best regards,
    Angelo
  • 0 in reply to Angelo Zhang87
    Genius 3455 points
    Hi Angelo,

    yes the battery responds to commands received from MCU. the host can change the battery by BatteryMode() command and read the status of the battery by BatteryStatus(). also the MCU read all variables of the battery such as temperature, voltage, charge, ...

    the charger IC is BQ24725A. i didn't have give any command to BQ24725A by host yet.

    i focus on the battery now. i need to know why the battery doesn't initiate broadcasting of charge information?
    must to do some tasks required before broadcasting?

    Best Regards, Ras
  • 0 in reply to Angelo Zhang87
    Genius 3455 points

    i also test another laptop battery.
    i disconnected the battery form another laptop and connected it the MCU.
    but this second battery also doesn't broadcast charging information.

  • 0 in reply to Ras Sharif50
    TI__Genius 11850 points
    Hi Ras,

    Please take a look at the Smart Battery Data Specification document here, especially Section 5.2 (Smart Battery or SMBus Host to Smart Battery Charger Messages) and Section 6.2 (Smart Battery-to-Smart Battery Charger Message Protocol):
    sbs-forum.org/.../sbdat110.pdf

    If the document above doesn't solve your issue, then I would recommend reading the smart battery's datasheet and checking with the manufacturer to see the exact communication protocol needed to communicate with the charger.

    Best regards,
    Angelo
  • 0 in reply to Angelo Zhang87
    Genius 3455 points
    Hi Angelo,
    form the smdat110.pdf: the smart battery broadcasts charging information to the charger and the host.
    unfortunately i don't have access to the batteries datasheet.
    is ti probable that some of laptop batteries don'r completely compliant with smart battery data specification?

    Best Regards, Ras
  • 0 in reply to Ras Sharif50
    TI__Genius 11850 points
    Hi Ras,

    You mentioned in an earlier reply that there is activity on SDA and SCL when the battery communicates with the host. Is there any activity on SDA and SCL when the battery tries to communicate with the charger?

    Also, I know you don't have the datasheet available, but can you give me any additional information about your battery, such as the manufacturer or part number? Without knowing what battery you're working with, I can't say whether or not the battery is fully compliant with the Smart Battery Data Specification.

    Best regards,
    Angelo
  • 0 in reply to Angelo Zhang87
    Genius 3455 points
    Hi Angelo,
    thank you for the reply.
    there isn't any communication between the charger and the battery.

    it is a 9 cells Megacell battery suitable for HP Dv4 laptop. i use ManufacturerName() command and read "SDI".
    when i use ChargingVotage() command, i read 12.6V constantly and when i read the charging current, the battery send 3.5A constantly.

    Best Regards, Ras
  • 0 in reply to Ras Sharif50
    TI__Genius 11850 points
    Hi Ras,

    For the sake of completeness, is it possible for you to test whether the charger can communicate with the host? That would help confirm whether or not the communication issue is on the battery end.

    SDI is by Samsung, but with the information you've given me, I can't find the product page or the datasheet for your battery. Here's their website, so can you take a look around and see if you can find the specific battery you're using? You can also check with them and ask about the exact communication protocol needed to communicate with the charger.
    www.samsungsdi.com/.../laptop.html

    Best regards,
    Angelo
  • 0 in reply to Angelo Zhang87
    Genius 3455 points

    Hi Angelo,

    thank you for the reply.

    i can't establish a communication between the charger and the host.

    the battery is not original. bellow is a photo of it:

    Best Regards, Ras

  • 0 in reply to Ras Sharif50
    TI__Mastermind 25800 points
    Hey Ras,

    If you have a logic analyzer to show communication between the charger and the host, I would recommend doing this next.

    We should also confirm if the charger is powered by either the input source and/or the battery voltage source.

    As a next step, I would also ask you to order BQ25725AEVM from the TI store in order to confirm whether this your board issue, a test setup issue, or a host communication issue?


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Genius 3455 points

    Hi Joel Hernandez,

    thank you for the reply.

    please consider a photo of the clock and data lines on my logic scope showing a command from the host to the battery:

    i temporarily put aside smart charging. i charge the battery using a constant-voltage supply( 12.6V ) currently.

    i will add BQ24725A to the system in the next phase.

    Best Regards, Ras