BQ27531-G1: Cycle count

Hello Janhavi,

I see that the cycle count is incrementing at a Q-passed Charge of about 1500. This shouldn't happen in your case since CC threshold is 4000 mAh.

For better assist you with this, may I see your gg file? I would like to confirm your configurations are correct.



Regards,
Jose Couso

Hello Jose,

Thank you for your reply.

Please see the attached gg file.

Regards,

Janahvi Rane

Board_15.gg.csv

Hello Jose,

Thanks again for the clarification.

But in our case, why true FCC is dropping during continuos charge? If the battery is fully charged (100% ) and still the power adapter is connected then FCC should remain constant, right? It should not reduce the CC threshold.

Regards,

Janhavi Rane

Hello Janhavi,

The FCC is stablished before discharge starts and is based on a simulation from full to empty for a specific temperature and anticipated load.

Notice how FCC decreased during "continuous charge". How are you continuously charging your device? 

Regards,
Jose Couso

Hello Jose,

Thank you.

We are using bq24192 battery charger management IC and 5V/3000mA external power supply for continuously charging our device.

Regards,

Janhavi Rane

Hello Janhavi,

I would definitely check the charger. See below how the current is jumping. Try doing a constant current once it hits the taper current, and see if this fixes the issue.



Regards,
Jose Couso

Hello Jose,

Okay, I will check with the constant current.

Regards,

Janahvi Rane

Hello Jose,

 Still few terms are not clear for me. I have following questions:

1) As I said before, cycle count is increasing  during charging, is it normal?

2) We have set taper current = 150mA. one condition for charge termination is that when Average Current is < Taper Current, So charge termination occurs when average current is less that 150 mA. As you said above try to do constant current, how to do that? 

3) How to stop passed charge from increamenting after the full charge condition(during continuous charge state)?

4) In our case, charger register ITERM[3:0] = Termination current limit bits are reserved so we can not set the termination current. we have ITERM[3:0]=0000. How to contro or set charge termination current?

Regards,

Janhavi Rane

Hello Janhavi,

1) As I said before, cycle count is increasing  during charging, is it normal?

The gauge checks for cycle count regardless of charging or discharging.

2) We have set taper current = 150mA. one condition for charge termination is that when Average Current is < Taper Current, So charge termination occurs when average current is less that 150 mA. As you said above try to do constant current, how to do that? 



3) How to stop passed charge from increamenting after the full charge condition(during continuous charge state)?


The gauge does this automatically once FC bit is set. Please see below. 



The problem here is the current is not constant for some reason. I would make a separate thread and ask the charger team for your specific charger device to see if the charger needs to be configured different.

Regards,
Jose Couso

Hello Jose,

Thank you so much for the explaination. It will be really great if you create a separate thread for bq24192 charger regarding the configuration.

Waiting for your reply.

Regards,

Janhavi Rane

Hello Janhavi,

I will create the thread for the charger team. Will get back to you with their response.

Regards,
Jose Couso

Hello Jose,

Thank you so much for your reply.

After conducting some test we have observed that some bits in charger are not set properly. 

I have following questions:

1. As charger team said, reduce the termination current level, but how to do that? charger register ITERM[3:0] = Termination current limit bits are reserved so we can not set the termination current. Here gas gauge is controlling the charger.

As per bq27531-G1 TRM(pg. 24): The fuel gauge disables the charger current termination and uses the coulomb counter for termination detection. Offset = 128 mA, Range = 128 to 2048 mA, Default = 256 mA

so here termination current is not considered?

2. After full charge of the battery when FC bit is set, EN_HIZ bit (Reg0) is also set to HIGH. As we have disabled the Hi-Z mode by setting EN_HIZ = 0. Why the charger is entering in Hi-Z mode?

3. During the charging, CHRG_STAT[1:0] (Reg8) =10= fast charging mode and when charging is full it changes to 00= not charging, but it should go to 11= Charge done, right?

4.CHG bit is always set to HIGH during the charging and also when the charging is full. But when FC bit is set it should clear, right?

5. Reg5: EN_TERM = The fuel gauge disables the termination detection to take over this function using the coulomb counter, Here coulomb counter means passed charge? In our case EN_TERM =0 means it doesn't take taper current in account for charge termination?

Refer below image:

6. If we want to change the charger from default mode to host mode (here GG_GHRGCTRL_DISABLE is set), how to do that? 

As per the bq24192 charger datasheet, to keep the device in host mode, the host has to reset the watchdog timer by writing 1 twice to REG01[6] before the watchdog timer expires (REG05[5:4]), or disable watchdog timer by setting REG05[5:4] = 00.

But REG01[6] and REG05[5:4] are reserved.

when GG_GHRGCTRL_DISABLE is set, WATCHDOG_FAULT bit is set to high = watchdog timer expiration. How to remove this expiration? What is the meaning or use of this watchdog timer expiration?

Regards,

Janhavi Rane