BQ27GDK000EVM: Charging current does not behaves as expected for the system constructed by BQ27z561EVM and BQ27GDK000EVM

Wenlong Wang

Part Number: BQ27GDK000EVM
Other Parts Discussed in Thread: BQSTUDIO

Hi,

due to the requirement of my current research, I have to use BQ27z561EVM battery gauge and BQ27GDK000EVM kit together to validate some battery models. I follow "Quickstart Guide for Gauge Development Kit" (http://www.ti.com/lit/ml/sluub24/sluub24.pdf) to connect these two instruments as the figure in sluub24.pdf:

The system is calibrated following the guides of current and voltage calibration. Now I meet a problem that during charging procedure, I set charge current as C/2 (1600 mAh), while the real charge current is only round 780 mA . Anyone could help me about that? I am newbie in this field, if any other information is needed for solving this problem, just let me know. I will update.

Thank you,

Wenlong

over 6 years ago

0 Onyx Ahiakwo over 6 years ago

TI__Guru* 76230 points

Hi Wenlong,
To charge a battery, you need a CC/CV profile. What is your CV? You may have already hit your CV and as such the current is already reducing.

thanks
Onyx

0 Wenlong Wang over 6 years ago in reply to Onyx Ahiakwo

Intellectual 275 points

Hi, Onyx.

Thank you for your reply.

The CV I am currently using is 4.2V. I have one more question that if I should upload my CC/CV profile to the gauge? If so, how can I do it? I was thought CC/CV profile is configured when I upload the Chemistry ID.

Here I attach the CC/CV profile I am using:

The problem I described before is found when I try to charge a 20%SOC battery.

I think it should be in the CC charging process, when the SOC is 20%, right?

Thank you,

Wenlong

0 Onyx Ahiakwo over 6 years ago in reply to Wenlong Wang

TI__Guru* 76230 points

Wenlong,
Provide a log file . Also to use the GDK properly, pls watch the video in the link below

training.ti.com/gauge-development-kit-gdk-overview

thanks
Onyx

0 Wenlong Wang over 6 years ago in reply to Onyx Ahiakwo

Intellectual 275 points

Thank you for your reply, Onyx.

From the video of that link, no information about uploading CC/CV profile to battery gauge I can find. Before start charging,

I think in my case, the CC/CV profile is already updated before I started cycling. I configured all the parameters suggested by the following guides and posts:

- How to perform a successful learning cycle with gauges (https://training.ti.com/how-perform-successful-learning-cycle-gauges)

- How to run an Impedance Track gas gauge learning cycle (https://e2e.ti.com/blogs_/archives/b/fullycharged/archive/2016/03/02/how-to-run-a-learning-cycle)

- CC-CV charging profile (https://e2e.ti.com/support/power-management/f/196/t/762439?tisearch=e2e-sitesearch&keymatch=charge%20profile)

I attach the parameters I set below:

I think the parameters are set and write to battery gauge correctly. The problem is caused by bqStudio doesn't show the SOC correctly during charging process, The figure is below is a snapshot during charging process:

According NCR18650B datasheet (https://www.batteryspace.com/prod-specs/NCR18650B.pdf), the current and voltage in the snapshot are correct, but the SOC is not correct. Do you think it is the reason of my problem?

Kindly regards,

Wenlong

0 Kang Kang over 6 years ago in reply to Wenlong Wang

TI__Mastermind 24870 points

You will also need to make sure you have the right chemistry default profile selected prior to running the learning cycle.

I would also check Qmax and Ra tables have been updated.

The accuracy can then be calculated following our blog post on e2e for the gas gauging accuracy calculation.

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BQ27GDK000EVM: Charging current does not behaves as expected for the system constructed by BQ27z561EVM and BQ27GDK000EVM