BQ40Z80: 7th cell calibration problem.

Maxim Fiodorov

Part Number: BQ40Z80
Other Parts Discussed in Thread: BQSTUDIO,

Hi everyone.

I have a problem with cell calibration by battery management studio 1.3.86.

I set each of 7 cells to 4V on resistors voltage divider. I eter the values for calibration (see attached picture). But I always get 7th cell near 3940mV ad not near 4000mV.

All other cells are near 4000mV.

Only if I manually adjust VC7 Sense Gain I achieve desired 4000mV at 7th cell.

Does anyone had the same problem with calibration by battery management studio 1.3.86.???

Is there any solution to this?

I attache 2 gg files with manual and battery studio calibration.

bq studio calibration.gg.csv

manual calibration.gg.csv

over 5 years ago

0 Kang Kang over 5 years ago

TI__Mastermind 24870 points

Hello Maxim I'm assigning this to device expert. Expecta response within 2 days.

0 Maxim Fiodorov over 5 years ago

Prodigy 180 points

I forgot to mention when I adjust manually VC7 Sense Gain the BAT pin voltage get adjusted correspondingly but it still inside 1% battery voltage error range.

I get the same phenomenon on my design and on evaluation board.

0 Andy Liu (BMS) over 5 years ago in reply to Maxim Fiodorov

TI__Guru 52115 points

The Cell 7 voltage is handled differently from the voltage of other cells. Let me try my EVM and see if there is a way to help you.

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

TI__Mastermind 24870 points

Please try on the test version (1.3.100), I believe this issue should be resolved.

Thanks!

0 Maxim Fiodorov over 5 years ago in reply to Kang Kang

Prodigy 180 points

I have tried 1.3.100 version of bq Studio.

The problem still exist.

0 Andy Liu (BMS) over 5 years ago in reply to Maxim Fiodorov

TI__Guru 52115 points

Hi Maxim,

I guess what you try is to follow the steps in Section 2.2 of the following app note and see if you can have better calibration results.

https://www.ti.com/lit/an/slua868/slua868.pdf

Andy

0 Maxim Fiodorov over 5 years ago in reply to Andy Liu (BMS)

Prodigy 180 points

slua868.pdf describe how to calculate the calibration coefficients. I am doing it myself to correct wrong calibration by Battery Management Studio program.

My problem is the wrong calibration by Battery Management Studio.

0 Andy Liu (BMS) over 5 years ago in reply to Maxim Fiodorov

TI__Guru 52115 points

I will report this issue to my software team so that they can double-check if it is necessary to update their existing code.

Andy

0 Shirish over 5 years ago in reply to Maxim Fiodorov

TI__Guru 57697 points

Do you get the same result in bqStudio if you uncheck "Calibrate Pack Voltage"?

0 Klaus over 5 years ago

Expert 1431 points

Hi Maxim,

I think in 7-Cell Application you don`t have to Calibrate VC6 Voltage.

Here is a part from the Application Report:

Klaus

0 Kang Kang over 5 years ago in reply to Klaus

TI__Mastermind 24870 points

Hello Klaus,

The bq40z80 7th cell measurement uses a different measurement from VC6. Are you able to accept the current performance of the device after calibration?

0 Klaus over 5 years ago in reply to Kang Kang

Expert 1431 points

Hi Kang,

so far it is ok for me.

I only wanted to share my experience.

Thanks.

Klaus

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BQ40Z80: 7th cell calibration problem.