BQ40Z80: Cell Current Values when Scaling

Antonio Fadhel

Part Number: BQ40Z80

Hi,

My customer is using the bq40z80 with a 40x current scaling factor. However, the Cell Current values do not seem to be scaled by the gauge so they max out at 32A. What is Cell Current used for? Just want to make sure there are no issues with these values maxing out.

Thanks,

Antonio

over 5 years ago

0 Dominik Hartl11 over 5 years ago

TI__Guru 61266 points

The cell currents aren't scaled as these are used for DOD0 calculations for each cell where the current has to be way below the 16-bit signed integer limit.

0 Antonio Fadhel over 5 years ago in reply to Dominik Hartl11

TI__Genius 9410 points

Hi Dominik,

If the cell currents are not scaled, then the gauge will not be able to store beyond 32.767A. This would result in incorrect DOD0 calculations for higher currents which would affect cell balancing calculations and gauging.

Can you please confirm this?

Regards,

Antonio

0 Kang Kang over 5 years ago in reply to Antonio Fadhel

TI__Mastermind 24870 points

Hello Antonio,

That is correct. It also results in incorrect resistance measurements and bad Qmax values as well.

0 Antonio Fadhel over 5 years ago in reply to Kang Kang

TI__Genius 9410 points

Hi Kang,

Is this a bug then? Just to confirm: the gauge does not scale Cell Current, so it is unable to see values beyond 32.767A even when current scaling is implemented, resulting in incorrect measurements? Can you confirm? Please note that the issue is specifically with the Cell Current values and not with the other current parameters which the gauge is scaling by the scaling factor as expected.

Thanks,

Antonio

0 Dominik Hartl11 over 5 years ago in reply to Antonio Fadhel

TI__Guru 61266 points

No, this is for DOD0 calculations, not DOD calculations. DOD0 implies very low current (because that's supposed to be an OCV measurement). That's all the gauge uses cell current measurements for. Therefore the saturation at very high currents doesn't matter as it won't be possible to estimate DOD0 in situations where current is that high.

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BQ40Z80: Cell Current Values when Scaling