BQ40Z50 incorrect Cell Voltages

Alexander Gierke

Other Parts Discussed in Thread: BQSTUDIO, BQ40Z50-R1, BQ40Z50

Hi,

i am using the BQ40Z50 with BQStudio for a BMS. First i update Firmware on Bq40Z50-R1 and do voltage calibration.
The Problem is that the gauge shows me different cell voltages than the multimeter.

All my cells have 4V but in gauge cell 2 and cell 3 have 4.4V.

Then i discharges the Pack for a new calibration but the difference is still the same. 3V Multimeter and 3.4V - 3.5V gauge.

I would like to start a leaning cycle, but if the gauge have the wrong voltages it will stop before the pack is totally charged.

What can i do to fix this problem?

Thanks for help.

over 8 years ago

0 Justin Erfan over 8 years ago

TI__Expert 3385 points

Hi Alexander,

Are you waiting for the cells to relax before taking a voltage measurement?

Also can you please describe your voltage calibration procedure?

Best,
Justin

0 Alexander Gierke over 8 years ago in reply to Justin Erfan

Prodigy 40 points

Hi Justin,

i fixed my problem. I had some reflow issues.
But i have another question about the dsg drive.
The DSG Pin has the same voltage like an adapter or lipo if connected.
I tried to disable it but there was no change and the voltage was constant.
how can that happened?

My design i like the typical application.

0 Justin Erfan over 8 years ago in reply to Alexander Gierke

TI__Expert 3385 points

Hi Alexander,

The DSG pin will read voltage high if the FETs are enabled. If you want to disable it, you can send a FET_EN command (to disable it) using bqStudio.

Best,

Justin

0 Alexander Gierke over 8 years ago in reply to Justin Erfan

Prodigy 40 points

Thank you Justin,

If I try to disable the DSG pin there is still a voltage of 8.3V at the DSG pin.
I removed the DSG FET and tested the FET pin. The Signals were ok. It has a pinvalue of 23V when FETs enabled and 0V disabled.
Maybe its a problem with the circuit?

Thanks
Alexander

0 Alexander Gierke over 8 years ago in reply to Alexander Gierke

Prodigy 40 points

Hello,

the BMS works fine now.
The problem was a connection between the pads of the DSG FET. I do not like power packages...
Justin thank you for your help .

Best,
Alexander

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BQ40Z50 incorrect Cell Voltages