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BQ27220: Fuel gauge does not use RAM Full Charge Capacity

Daniel Bode
Prodigy 60 points
Part Number: BQ27220
Other Parts Discussed in Thread: BQSTUDIO

After successfully calibrating the fuel gauge (GPC) I started to test the SOC calculation accuracy. All new CEDV parameters are not written to OTP but RAM.

I have noticed that even though I set the Full Charge Capacity to 3250mAh, the fuel gauge seems to use the default (ROM) Full Charge Capacity of 3000mAh.

 

Full charge test profile (bqStudio log):

The issue is that the fuel gauge reports 100% SOC too early, presumably because it uses a Full Charge Capacity that is too low.

How can I make sure that the fuel gauge uses the Full Charge Capacity from RAM?

  • 0
    TI__Guru 62646 points

    You can check this on the EVM (I just did) using the following sequence:

    1. unseal the gauge (the gauge is sealed by default)
    2. issue the ENTER_CFG_UPDATE command
    3. change FCC in RAM (CEDV Profile 1 in Gas Gauging) to 3250mAh
    4. issue the EXIT_CFG_UPDATE_REINIT command
    5. refresh registers -> FCC will now be 3250mAh

  • 0 in reply to Dominik Hartl11
    Prodigy 60 points

    Thanks for the answer. But this doesn't work for me.

    I can update the RAM FullChargeCapacity:

    But the register always uses a ROM Default profile:

    ROM Default Profile 2:

  • 0 in reply to Daniel Bode
    TI__Guru 62646 points

    Please write the exact steps that you took. Make sure that you disable auto-refresh (click on the green line in the dashboard view; it'll turn red).

    I tested this on my EVM with the steps from my previous post so this will also work on your EVM if it's done exactly the same way.

    The gauge must be in configuration update mode and you must exit configuration update mode with re-initialization after changing settings for this to work.

  • 0 in reply to Dominik Hartl11
    Prodigy 60 points

    Now it worked! Not sure what I did wrong before. 

    With ENTER_CFG_UPDATE and EXIT_CFG_UPDATE_REINIT it even works with the SmartFlash tool. That is all I wanted. Thanks a lot.