BQ4050: maxerror becomes 100%

Sunrain

Part Number: BQ4050
Other Parts Discussed in Thread: BQ40Z50

Hello

BQ40Z50 has finished learning, and then set it to shutdown mode. Why does maxerror return to 100% when it wakes up again? Shutdown must be set. Is there any way to prevent maxerror from becoming 100%. Otherwise, it takes too much time to re-learn.

Thanks

over 3 years ago

0 Wyatt Keller over 3 years ago

TI__Guru** 105770 points

Hello Jingming,

Can you confirm that the Learned FCC value saved in DF is the save before and after the POR (Power On Reset) event?

I think this thread may also be helpful for MaxError operation: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1000453/bq4050-maxerror-and-fccx-cf-flags

Sincerely,

Wyatt Keller

0 Sunrain over 3 years ago in reply to Wyatt Keller

Intellectual 615 points

Hello
My batteries are all learned, and the maxerror before shutdown is 2%, which is different from what the link says.

This is a phenomenon reported by customers, I have no data here

0 Wyatt Keller over 3 years ago in reply to Sunrain

TI__Guru** 105770 points

Hello Jingming,

The MaxError will increase to 100% after a POR since we have to base the RemCap on rough estimation using the 10 voltage to DOD points saved in DF, since the CEDV algorithm relies heavily on coulomb counting which is saved in RAM (lost on POR) it needs to relearn the actual RemCap after a battery cycle.

Sincerely,

Wyatt Keller

0 Sunrain over 3 years ago in reply to Wyatt Keller

Intellectual 615 points

Hello,
It means that after entering shutdown, it must be re-learned after restarting? Is there no other way?
Relearning takes too much time.

0 Wyatt Keller over 3 years ago in reply to Sunrain

TI__Guru** 105770 points

Hello Jingming,

The MaxError will report 100%, the gauging itself may be okay if the voltage for the chemistry has a slope to the OCV and the cell is relaxed so the voltage is stable. But it will take a new FCC update in order for the MaxError to decrease.

Sincerely,

Wyatt Keller

0 Sunrain over 3 years ago in reply to Wyatt Keller

Intellectual 615 points

Hello,
Does it mean that after shutdown, I have to learn it again when wake up again? There is no other way?

+1 Alexander Mazany over 3 years ago in reply to Sunrain

TI__Genius 11770 points

Hello Jingming,

Unfortunately, you will have to learn again since that data is lost on reset. But like Wyatt said, the gauging may not be too bad, maxerror just tells you that the data could be off, not that it is off. It depends what you do with the battery while it is shutdown, the voltage, and the chemistries OCV curve.

For example, if you had a LFP battery in the flat region, the gauge's REMcap estimation could be very far off, which is what maxerror is telling you. But if it were in the steeper regions such as the beginning or end of DOD, the estimate may be quite good. Depending on the application, you may not have to dedicate time to learning again; you could just let it learn automatically as it is used.

thanks,

Alex M.

+1 Sunrain over 3 years ago in reply to Alexander Mazany

Intellectual 615 points

Hello,
I see, the charge and discharge data is not very good after maxerror reaches 100% again, we just don't want to take the time to recycle
thanks

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BQ4050: maxerror becomes 100%