BQ27426: Reason for large change in TRUE FCC when charging a new battery?

Wang Dong

Part Number: BQ27426
Other Parts Discussed in Thread: BQSTUDIO

Hello,

Background: FS file based on a new battery with a reserve capacity of 350mAh.

Using a new battery, load the FS file made based on the new battery.

Different charging current 200mA and 1A。There will be a large change in TRUE FCC, and the True Fcc change is almost the same。

1、Please analyse the logs to see what caused the drastic change in the TRUE FCC?

2、Why does the TRUE FCC change by the same amount for different SOH batteries?

3. Is the above problem, related to FS files?Which specific configuration is the problem?

Attached is the log grabbed using TI demo board + BqStudio.

TI Demo+Bqstudio,True Fcc Test.zip 6064.0418_New_Bat_FS_withChemID_0419.gm.zip

8 months ago

0 Adrian 7 months ago

TI__Mastermind 22031 points

Hello Wang,

I will need some time to look over the files. I will hopefully get back to you tomorrow.

Sincerely,
Nick Richards

0 Adrian 7 months ago in reply to Adrian

TI__Mastermind 22031 points

Hello Wang,

Thank you for your patience. This drastic change in True FCC is caused because that register is reporting
the FCC flt value. To fix this, set OpConfigB[SMOOTHEN] = 0.

I would also recommend reading this post as it talks in depth about FCC.
e2e.ti.com/.../bq27426-reason-why-different-battery-fuelgauge-get-different-fcc-values-on-initial-power-up

Sincerely,
Nick Richards

0 Wang Dong 7 months ago in reply to Adrian

Intellectual 540 points

Hello，

Not quite sure what you mean.

Is it possible to use a log and plot graphs to illustrate this?

Adrian said:
Thank you for your patience. This drastic change in True FCC is caused because that register is reporting
the FCC flt value. To fix this, set OpConfigB[SMOOTHEN] = 0.

So we were looking for, based on our application, a way that the FCC could correctly match the battery capacity.

Thanks a lot. This is the same question I asked. We have a demanding application with no full charge or discharge, a charge of only 50mAh and very little discharge action.

Adrian said:
I would also recommend reading this post as it talks in depth about FCC.
e2e.ti.com/.../bq27426-reason-why-different-battery-fuelgauge-get-different-fcc-values-on-initial-power-up

0 Adrian 7 months ago in reply to Wang Dong

TI__Mastermind 22031 points

Hello Wang,

Yes, you can change OpConfigB[SMOOTHEN] within the data memory of the gauge and then run new test to see if the true is changing drastically like you seen before.
We have seen similar applications like yours and the gauge still still be able to report accurate FCC. It is important that there is rest time after charge and
discharge so that the gauge is able to make new FCC calculations.

Sincerely,
Nick Richards

Power management

Power management forum

BQ27426: Reason for large change in TRUE FCC when charging a new battery?