BQ40Z50-R1: How do you determine what Maximum Cell Balance Time Values to use?

Ken Cowan

Part Number: BQ40Z50-R1

Tool/software:

The default value for Bal Time/mAh Cell 1 is 240 s/mAh and for Bal Time/mAh Cell 2-4 is 360 s/mAh. How were these default values determined and how do I adjust them for my application? I am getting packs that exceed these values after only a couple years and are disabling themselves while all the individual cell parameters such as OCV, QMAX, impedance are all relatively close. Is there a way to calculate what these settings should be?

Thanks,

1 month ago

0 Alan Frias 1 month ago

TI__Mastermind 26035 points

Hello,

This question has been assigned and will be reviewed when possible. In the meantime please attach your .gg and/or .log files associated with this project.

Thank you,
Alan

0 Miguel Castro Gonzalez 12 days ago

TI__Intellectual 902 points

Hello Ken,

Please see these app notes about the cell balancing. Some come with formulas.

Comparisons_between_gauges.pdf cell_Balancing_bq20zxx.pdf

-Miguel

0 Miguel Castro Gonzalez 12 days ago in reply to Miguel Castro Gonzalez

TI__Intellectual 902 points

Please also read the TRM about cell balancing, section 7.2

0 Ken Cowan 10 days ago

Prodigy 20 points

Thanks for the app notes on balancing. I just realized I did not ask my question correctly. What I really want to know is how to calculate the CB Max Threshold which defaults to 240 hours. This is what is disabling my packs prematurely. How was this value of 240 hours calculated? It is not discussed at all in the reference manual or either of the app notes you have attached.

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BQ40Z50-R1: How do you determine what Maximum Cell Balance Time Values to use?