BQ24080: Not able to charge battery at set current (~800mA) in CC mode

Hello
A couple of things to check:
1.) Input voltage and output voltage. For 800mA out could need 500mV (Vin-Vout) for regulation.
2.) Does the device seem to be heating or have significant thermal rise?
3.) Check voltage at ISET. It will be 2.5V when in CC and at target current.

Hi

Any update on this problem?

Hi Bill,

Sorry for the delay!

Yes, I checked overall working of BQ24080. Below are my observation:

When battery is not connected for charging:

1. Input votlage, SYS_5V = 5.1V.

2. Output voltage, Backup_Batt+ = 4.2V.

3. Icharge = 0.0A

4. Voltage on STAT1 = 0V

5. Voltage on STAT2 = 3.3V

6. VSET = 0.01V

Pre-condition --> Battery voltage = 3.5V @ Idischarge = 0.7A.

After removing the load, I have connected the battery with the charger and observed the following values:

1. Input votlage, SYS_5V = 5.1V.

2. Output voltage, Backup_Batt+ = 4.2V.

3. Icharge = 0.350A

4. Voltage on STAT1 = 0V

5. Voltage on STAT2 = 3.3V

6. VSET = 1.6V

IMy observations:

Here, STAT1 and STAT2 pins condition are not varying for mode changes.

It looks like it always detects battery voltage at 4.2V that is VO(REG) limit and starts voltage regulation mode. It is never entering into fast charge mode.

Below is the layout for your reference.

Hi

Thanks for the details.

Voltage on STAT1 = 0V and Voltage on STAT2 = 3.3V, STAT1 = ON and STAT2 = OFF this would be Fast Charge in progress.
Battery voltage is 3.7V but when connected the voltage goes to 4.2V with 350mA of current.
Voltage at SET pin is 1.6V also indicating unit is in voltage taper, CV mode.

ISET pin is a sample of the input current (current mirror) with a ratio of about 1 to 322. If you are seeing 1.6V and R-ISET is 1k the output current is about 515mA.
During CC mode VSET will be 2.5V.

I suspect there is some resistance between the battery and OUT pin, could be connections, gas gauge sense R, battery protection circuit or others. The effect is to increase the voltage at OUT as current is supplied to battery during charge and unit enters CV mode early.

Can you check the battery voltage at the cell vs OUT pin?
Also resistance in the battery return will have same behavior.

Hi

Any update on this problem?

Hi Bill,

We are debugging for different possible issues. Yet not able to catch the point.

As per your suggestion, I checked the impedance between the battery connector and charger output pin, it is showing 0.10E (100mohm). I think; that can be neglected as we are seeing the same impedance value in the EVK board also. (Where we are getting the same result as it is on board.)

Now we are trying to debug it with Evaluation board first by executing a full charging cycle.

Let me know if you need me to measure at other points on board. Also, below is the full schematic with the fuel gauge IC connection.

Thanks,

Dhvanish Parekh