BQ40Z60: BIST(build-in self-test) failure

Shenhua Zhang

Part Number: BQ40Z60
Other Parts Discussed in Thread: BQSTUDIO

Hi expert,

In customer's battery back-up unit, the BIST(build-in self-test) is configured to drain 25% from the cells at the time of execution. It will than wait until the pack reaches a charge >= 95%. If it cannot reach that level within the allotted time the BIST will fail.

Log has shown these:

Service life: 538.00 days

Discharge cycle Count: 0.00 cycles

Based on it, customer has two questions:

1. The service life states 538 days. So in some way it seems extremely odd to me to see a cycle count of zero in this field.

2. Do you think there's an issue with cell balancing in the design, which is leading to a premature charge termination, and eventual BIST time out.

over 5 years ago

0 Andy Liu (BMS) over 5 years ago

TI__Guru 52115 points

Hi Shenhua,

What does this Service life mean? In addition, is the Discharge cycle Count the same as the Cycle Count reported by bq40z60?

Andy

0 Shenhua Zhang over 5 years ago in reply to Andy Liu (BMS)

TI__Prodigy 640 points

Hi Andy,

"Service life" is the lifetime in bq40z60. Discharge Cycle Count is the same as the Cycle Count.

This failure is not a single failure, a great number of them fail with the charging cycle timeout.

Please help comment.

0 Kang Kang over 5 years ago in reply to Shenhua Zhang

TI__Mastermind 24870 points

Shelf life can also age a battery cell. It is better to find out more about what is happening during the application here.

0 Shenhua Zhang over 5 years ago in reply to Kang Kang

TI__Prodigy 640 points

Hi Kang,

Any advice on what we should check, to find out more?

0 Damian Lewis over 5 years ago in reply to Shenhua Zhang

TI__Mastermind 34775 points

Hello Shenhua,

What the cycle count threshold (CCT) set to? Also what's cycle count percentage? Did they check whether the gauge never reached 95% or greater, or did the discharge circuitry in the BIST didn't work? What's the present state of the gauge? Is it fully charged?

0 Harry Zhang13 over 5 years ago in reply to Damian Lewis

Intellectual 495 points

I read config data from gauge, it shows below:

Gas Gauging

Cycle

Cycle Count Percentage

Settings

Configuration

IT Gauging Configuration

d67f

hex

so i think CCT=1.

for other questions, i will double confirm and answer later.

thanks,

Harry

0 Kang Kang over 5 years ago in reply to Harry Zhang13

TI__Mastermind 24870 points

Please provide us a gg.csv file.

The other thing is can we take this battery pack out and dump an srec and use bqStudio to log and run a quick cycle test to see if cell cycle works appropriately.

0 Harry Zhang13 over 5 years ago in reply to Kang Kang

Intellectual 495 points

Thank you! I have provided gg.csv file to Shenhua, he will forward to you, and i will try your suggestion once i receive the battery.

0 Shenhua Zhang over 5 years ago in reply to Kang Kang

TI__Prodigy 640 points

Kang,

Please help close this E2E ticket, I have moved to JIRA with gg file attached.

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BQ40Z60: BIST(build-in self-test) failure