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BQ35100: Trying to operate in Accumulator mode

Carolus Andrews
Mastermind 22385 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO

Team,

I have a customer working with BQ35100 for monitoring their battery, and working to do the calibration using the bqstudio.

After hooking up their load, the current or the charge accumulation shown is 0mA. They are able to read the voltage though. Ideally, they want BQ35100 to work in accumulator mode, and they would like to read Voltage, Current, and Charge Accumulation. Are there any specific commands to set to see the current and charge accumulation?

 They have currently made connections as per the diagram shown on page 5 of the Evaluation Module.

Is there a way to know the actual current consumed by the load using BQ35100?? They are assuming that they are reading 0mA because it is the discharge current from the battery. Is there a better way for me to measure the discharge current?

 

 

  • 0
    TI__Guru* 76230 points
    Hi Carolus,
    The customer has to configure the gauge to work in accumulator mode. ps see the TRM for details on how to set it to function in accumulator mode.

    pls see video as well
    r.search.yahoo.com/.../RS=CNUwJXnd9y76h0Cwir0UZoseu28-

    Hope this helps.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    TI__Mastermind 22385 points

    Onyx,

    We understand the device needs to be placed in accumulator mode. We've already referenced the TRM, and this is what it has to say about it:

    It says the data is provided over I2C, but makes no mention of the protocols needed to retrieve the data. Commands, register locations, anything. This is what we need.

    Also, you didn't address my second question at all. Can you comment on the measuring of the discharge current?

  • 0 in reply to Carolus Andrews
    TI__Mastermind 24870 points
    For accumulator mode, the current is just measured through SRN and SRP on the sense resistor. If you needed to measure the learning load for EOS mode, the only way is to size the discharge FET and resistor accurately to assume a particular learning load.
  • 0 in reply to Kang Kang
    TI__Mastermind 22385 points

    Kang and Onyx,

    The problem is not just central to accumulator mode though. The current read through the GUI is negative. Instead of reading 100mA, they are reading -100mA. Similarly, their charge accumulation is negative. See below:

    They are also facing some form of calibration of current issue. They don't have this problem on the EVM, as by default, current drawn in is 0mA.

    With the BQ35100 on their own board, the current drawn is 1mA, but the chip is  measuring it as 5mA. i.e. there is an 4mA offset.

    They are performing the following calibration steps:

    Toggle Cal_mode

    calibrate voltage

    CC offset calibrate

    Board offset Calibrate

    provide 1A current and calibrate

    toggle Cal_mode

    but the default current on the gauge start is again -5mA (5mA, with the negative issue as mentioned above)

    Thoughts?

  • 0 in reply to Carolus Andrews
    TI__Guru* 76230 points
    Hi Carolus,
    Can they check to make sure there isn't current being drawn that is passing through the sense resistor? They can use a power supply instead of a battery, that has current measurement to check this. They should as do a schematic review of their board, comparing it to our EVM reference schematic.
    thanks
    Onyx