BQ40Z50: Charge Completion Issue with BQ25820 and BQ40Z50 Fuel Gauge – LiFePO4 4S1P Battery Pack

Jeevabharathi R

Part Number: BQ40Z50
Other Parts Discussed in Thread: BQ25820

Hi Team,

We’ve raised an issue regarding charge status completion with the BQ25820 charger IC and BQ40Z50 Fuel gauge.
Link: [TI E2E Forum – BQ25820 Charge Completion Issue] (TI E2E Forum)

System Details:

Battery Type: LiFePO4
Configuration: 4S1P
Fuel Gauge: BQ40Z50

Issue Description:

We suspect that during the final stages of charging (constant voltage and termination phase), the fuel gauge ( BQ40Z50) is turning off the battery FET, which interrupts the charging process.

As a result:

The BQ25820 charger does not complete its termination properly.
It continues attempting to charge the battery, which appears to be open-circuited due to the FET being turned off by the fuel gauge.

We are unable to confirm whether the fuel gauge is indeed turning off the FET. We’ve attached the fuel gauge register values for reference.

BQ40z50 reg2.png

Could you please help us understand what is happening in the fuel gauge during this phase and guide us on how to resolve this issue?

Thank you for your support.

Thanks,

Jeevabharathi

15 days ago

0 Alan Frias 15 days ago

TI__Mastermind 30790 points

Hello,

This question has been assigned and will be reviewed by someone on the team when possible.

Thank you,
Alan

0 Miguel Castro Gonzalez 6 days ago

TI__Intellectual 2792 points

Hello Jeevabharathi,

SS triggered. This is the safety feature indicating any of the safety triggered. Then I see COV (Cell Overvoltage) triggered. Do you have a log file where you can see the voltages of the cells when they were being charged? The log file will tell you the status of the gauge, the voltages of the cell, and then when it changed the state of the FETs.

-Miguel

Power management

Power management forum

BQ40Z50: Charge Completion Issue with BQ25820 and BQ40Z50 Fuel Gauge – LiFePO4 4S1P Battery Pack