• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 4 answers
  • Subscribers 63 subscribers
  • Views 385 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: Current measurement depends on operational mode

corey
Prodigy 110 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO, EV2400

After loading the device with the default firmware using bqSudio I started calibrating the device. For calibration the technical reference manual states that device needs to be put into ACC mode. When calibration is complete if I read the current register, either with bqStudio or my host microcontroller, I see a very accurate value for current. However, as soon as I switch to EOS mode and take another reading the current value changes dramatically despite no actual change in the actual load current. If I change back to ACC mode and read the current register again it is back on target. In ACC mode the current tracks reality well if I change the load, so I have some confidence that the calibration was completed successfully, but our goal is to use EOS mode.

Where should I start looking to troubleshoot this? 

Thanks.

  • 0
    TI__Guru** 105760 points

    Hell Corey,

    Have you followed the EVM user's guide for doing calibration? Do you have an EV2400 to test with?

    You will need the EV2400 to upload the chemID. www.ti.com/.../sluubh7.pdf

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    Yes, I am using an EV2400 and I have followed the calibration instructions. I uploaded chem ID 622 though this likely is not an exact match for our battery. I would not expect the chem ID to affect the current calibration however. Please let me know if that's not the case.

    My procedure to reproduce the problem is as follows:

    1. Enter ACC mode using the "Data Memory" tab and selecting configuration to change GMSEL1:0 to be 00 in the operation config A register.

    2. Go to "Calibration" tab. Under commands click unseal.

    3. Apply known current and enter the value (in my case -540 mA) into bqStudio and click "Calibrate Gas Gauge." Success is reported with the green check mark.

    4. Go to "Registers" tab and click refresh. At this point I observe about 540 mA for the current value as expected.

    5. Enter EOS mode using the "Data Memory" tab and selecting configuration to change GMSEL1:0 to be 10 in the operation config A register.

    6. Go to the "Registers" tab and click refresh. At this point I observe 372 mA for the current value.

    Based on this thread: https://e2e.ti.com/support/power-management/f/196/p/611494/2255360?tisearch=e2e-sitesearch&keymatch=bq35100%2525252520ccgain#2255360, I should see a values of CC Gain and CC delta that are close to the value of my current sense resistor when viewed from bqStudio which is true. I have a 100 mOhm resistor and I'm seeing ~102 in bqStudio. 

    I've attached the data memory exported as gg.csv in case it is helpful.

    1346.data_memory.gg.csv

  • 0 in reply to corey
    Prodigy 110 points

    One other thing I should mention. In the above procedure if in step 1 if I instead make sure the gauge is in EOS mode then the calibration succeeds and current readings are then valid in both EOS and ACC mode.

    Thanks.

  • 0 in reply to corey
    TI__Guru** 105760 points

    Hello Corey,

    I'll take a look and confirm on my side if the calibration doesn't transfer between modes. It should work with calibrating in ACC mode.

    Right now I would recommend you calibrate in EOS mode if you are able to get accurate current measurements.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    I noticed the AD I offset was set to a large negative value. I'm not sure what impact that could have as it doesn't appear to be documented anywhere. However, after re-flashing the firmware and performing calibration again from scratch the AD I offset is zeroed and the gauge current readings appear valid again.

  • 0 in reply to corey
    TI__Guru** 105760 points

    Hello Corey,

    Could the data been accidentally changed? Now it is working in both modes while calibrating in ACC mode?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 110 points

    Yes, I found a mistake in my code that was writing some memory locations unintentionally. Specifically, AD I offset, Int Temp Offset, Ext Temp Offset and Pack V offset were likely corrupt. Yes, now it is giving me valid current in both modes.

    Thanks.

  • 0 in reply to corey
    TI__Guru** 105760 points

    Hello Corey,

    Glad to hear you were able to fix the issue.

    Sincerely,

    Wyatt Keller