BQ28Z610-R1: VCT condition of cell voltage,average current,and two consecutive 40s are reached,but FC cannot change to 1

When average current ＜3950mA,it takes much more time than 80s,it takes more than 180s,why it hanppen? 

Hello,

The battery is used for fast charge,so according to the charge method,it should stop charge at 2700mA,otherwise the battery will be overcharged and there will be much risk for battery.

When the temperature is over 45℃,FC cannot change to 1 after 80s,but if the temperature is lower than 45℃,FC can change to 1 after 80s.  is it related to T3 charge inhibit ? 

How to understand this?  Thanks.

Could I change T3 from 45℃ to 60℃？Are there any effects on it? what are the risk?

Hello Ran,

In the log provided, the Charge Inhibit was never set. But, you can check if charge inhibition happens by monitoring IN bit from the ChargingStatus() register.



Also, looks like CHGIN bit from Settings: FET Options is not set. This indicates if charging or pre-charging should be disabled in the event of charge inhibit. 

Ran Zhang said:

Could I change T3 from 45℃ to 60℃？Are there any effects on it? what are the risk?

You can try this. The risk is charging is allowed at temperatures up to 60C.

Regards,
Jose Couso

Actually,before change T3 from 45℃ to 60℃,it can be allowed charging. because IN is off .

I have tried to change T3 from 45℃ to 60℃,When the temperature is over 45℃,FC can change to 1 after 50~70s. During 45~60℃，it's being Standard Temp but not High Temp. 

Any other risk of this change?

IN bit is set to be 0,Why can't it trigger VCT as normal. We need charge battery with low current between 45℃ and 60℃ but not cut off current immediately.

Hi Ran,

For low charging current between 45C and 60C, you can adjust the High Temp Charging 



Regards,
Jose Couso

How to adjust? I mean we need to gauge trigger VCT as normal when temperature is between 45C and 60C.

Hello Ran,

It looks like the main problem you were experiencing was the gauge entering CHG INHIBIT. I would set T3 to 60C. the gauge will suspend any charging after 60C. 

To better understand the charging algorithm, please see below. The gauge changes charging current based on temperature and cell voltage.




If you are still having issues, please share the latest configuration and log files.

Regards,
Jose Couso

T3=60.rarAttachment is the gg and log file.

Hello Ran,

It looks like the device is entering Maintenance Charge. 

Ran Zhang said:

I have tried to change T3 from 45℃ to 60℃,When the temperature is over 45℃,FC can change to 1 after 50~70s. During 45~60℃，it's being Standard Temp but not High Temp. 

Do you have the log file when this happened? Also what is your chargers taper current set to?

Regards,
Jose Couso

 Here the pictures show differences between change T3=60 before and after. the charging voltage and charging current change from  High Temp to Standard Temp.

Hi Ran,

The pictures do not help. I am interested to see if maintenance charge was set when you said VCT happened. 

On the T3=45, it looks like charge INHIBIT did not happen. Charge Inhibit happens when charging current and charging voltage are forced to zero.

Try setting the taper current 10% higher than the charger taper. 

Regards,
Jose Couso

How to see if maintenance charge was set when VCT happened? 

Hi Ran,

From your settings, you have Maintenance Charging set to 44 mA. Whenever you see 44 mA in charging current, this is when maintenance charge is triggering. 



Regards,
Jose Couso

What's effects  will this have? if maintenance charge was set when VCT happened.

What should I do? Change any settings?

Hi Ran,

The maintenance charge does not have any bad effect. Maintenance charge happens when VCT conditions are not met at full charge termination. 

Maintenance charge can be monitored by the MCHG bit. This bit will clear when:
1- Charge/Discharge is detected
2- Charge Inhibit or charge suspend happens.
3- Pre-charge is active

Maintenance charge will help battery cell charge to the fullest capacity. I would make sure the charge suspend temperature is set where you do not want any more charging. Unfortunately, due to the extremely high taper current, you might be having problems meeting VCT. Please set T4 threshold to where you wish to stop charging completely. 

Regards,
Jose Couso

So back to my question,Why this hanppen? When T3=45,if temperature is over than 45，VCT trigger time is more than 80s such as 236s or 138s;When  T3=60,if temperature is over than 45，VCT trigger time is ≤80s.

Hi Ran,

I would say it is related to the charging current. When T3 = 60, the charging current was set to 5400 mA. 

Can you then set High Temp Charging to 5400 mA with T3 = 45? 

Regards,
Jose Couso

After setting High Temp Charging to 5400 mA with T3 = 45,if temperature is over than 45，VCT trigger time is ≤80s. 

So VCT is related to the charging current, If the high temp charging current is lower than taper current, it can cause long time for VCT ,is it right?