BQ40Z80: learning cycle failed after the charge

Bill Zhang2

Part Number: BQ40Z80
Other Parts Discussed in Thread: BQSTUDIO

Hello all,

I have been trying to complete a learning cycle using the BQ40Z80 and a 7S2P battery pack (6600mAh).I need that work at 3.05V to 4.15V.I set the design capacity settings (Design Capacity mAh = 6000mAh, Design Capacity cWh = 15120cWh, Design Voltage = 25200mV) The FC Set Voltage Threshold is set to 4150mV. Charge Term Taper Current is set to 1000mA, Dsg Current Threshold is set to 300mA, Chg Current Threshold is set to 500mA, Quit Current is set to 250mA， Term Voltage is set to 21350mV.

Here is a short summary of the procedure:
1. Update the chem id.

2. Send FET enable(0x22)

3. Discharge Battery to Empty and rest 5 hours Until REST = 1.

4.send IT (Gauge) enable command (0x21)

4.Charge the battery to full and wait until FC=1.

Rest 2 hours until VOK = 0,RDIS=0 ,REST = 1.But the Lstatus do not change to 0x05.

why the Lstatus do not change to 0x05???

over 5 years ago

0 Andy Liu (BMS) over 5 years ago

TI__Guru 52115 points

Hi Bill,

I have assigned your question to my colleague and he will provide the answer.

Andy

0 Bill Zhang2 over 5 years ago in reply to Andy Liu (BMS)

Prodigy 40 points

Hi Andy,

Thanks，please let your colleague reply me as soon as possible!!

0 Andy Liu (BMS) over 5 years ago in reply to Bill Zhang2

TI__Guru 52115 points

Hi Bill,

Do you have a bqStudio log that can shared with us? Thanks.

Andy

0 Mason Liu over 5 years ago in reply to Bill Zhang2

TI__Expert 4035 points

Hi Bill,

Why your Charge Term Taper Current is set to 1000mA? We recommend the taper current should be less than C/10 to ensure that battery gets properly fully charged.

And can you share the bqstudio log with us like Andy said in another reply?

Thanks.

Best regards

Mason

0 Bill Zhang2 over 5 years ago in reply to Mason Liu

Prodigy 40 points

Hi Mason，

Sorry，i did not save the log.

I had changed the Charge Term Taper Current to 200mA，which is less than C/10.I charged battery to full and relaxed 2h,the Lstatus did not charge to 0x05,but I continued to do the cycle,discharge battery to empty and relaxed 5h,it charge to 0x05.And then I complete a full charge-relax-discharge-relax cycle,Lstatus charge to 0x06,it means the learning successful???

Thanks.

Best regards

Bill

0 Mason Liu over 5 years ago in reply to Bill Zhang2

TI__Expert 4035 points

Hi Bill,

0x06 means you update the Qmax and resistance table in learning cycle. You can check this app note: https://www.ti.com/lit/an/slua848/slua848.pdf.

Thanks.

Best regards

Mason

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BQ40Z80: learning cycle failed after the charge