BQ40Z50: LFP cell cannot meet valid charge termination condition due to poor cell consistency

Kailun Liu

Expert 3003 points

Part Number: BQ40Z50
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Dear team,

My customer met a question in 4S1P LFP cell. Full charge V=14V(3.5V per cell).

Set V term=150mV, I term=200mA. RSOCL=1.

However, due to the poor cell consistency in LFP, some cell will reach 3.7V first and trigger OVP before valid charge condition meet. Current > 200mA, RSOC=99% at this time.

Is any configuration could help on this situation?

11 months ago

0 Anthony 11 months ago

TI__Mastermind 28450 points

Hi Kailun,

Is the cell balancing functionality already enabled in this gauge? If you could share the .gg file of the gauge settings and the bqStudio .log file of the situation occurring, we could take a deeper look into the issue.

Regardsm

Anthony Baldino

0 Kailun Liu 11 months ago in reply to Anthony

TI__Expert 3003 points

Thanks Anthony,

Test to find CB did not work. Can you help to review the external CB circuit which based on transistor?

0 Anthony 11 months ago in reply to Kailun Liu

TI__Mastermind 28450 points

Hi Kailun,

Can you please confirm that the orientation of the transistor? The orientation seems to be backwards compared to the reference design:

Regards,

Anthony

0 Kailun Liu 11 months ago in reply to Anthony

TI__Expert 3003 points

Hi Anthony,

The picture you shared is mosfet, customer is using transistor to do CB. I think the orientation is correct.

0 Anthony 11 months ago in reply to Kailun Liu

TI__Mastermind 28450 points

Hi Kailun,

Understood, if the orientation is correct then I believe the hardware is ok here. Can you please share the .gg file of the gauge settings and a bqStudio log file of the situation above so we can take a better look into the gauge?

Regards,

Anthony

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BQ40Z50: LFP cell cannot meet valid charge termination condition due to poor cell consistency