‌Inquiry regarding charge status on bq24250

Hi Okui-san,

Did the above happen consistently when you plug in the battery slowly and fast? How long the charge will last when you plug in the battery quickly? From the charger side, I don't expect this to happen. The fully charged battery will only start re-charging when the battery voltage dropped to 100mV below the regulation voltage. What is the battery regulation voltage programmed in this case?

Thanks,

Wenjia

Wenjia-san, 

Thank you for your prompt reply. 

With regard to your questions, please see my comment as below;

Did the above happen consistently when you plug in the battery slowly and fast?

=> Yes. This phenomenon is consistently happened on both cases.

How long the charge will last when you plug in the battery quickly?

=> The charge is lasted for few seconds (less than 10sec). After finished the charge, the charger status on GUI is transited into "Charge Done".

What is the battery regulation voltage programmed in this case?

=> On both cases, the Battery Regulation Voltage is 4.20V, as shown on the GUI image in attached report above.

If you have any further information needed, please feel free to ask me.

We thank you once again for your information. 

Best regards, 

Okui-san,

Thanks for the information.

To make the re-charge happen, the VBAT voltage will need to be below the re-charge threshold for 32mS. I've tried with the 250 EVM but could not re-produce the same performance. Can you capture the VBAT and IBAT signal from the beginning of battery plug in? If possible, please put 4V offset at the scope channel for VBAT so that we can see the exact voltage value better.

Thanks,

Wenjia

Wenjia-san,

Thank you for your continuous support towards the inquiry regarding bq24250 from our customer.

In accordance with your requirement, I have measured the phenomenon on bq2425xEVM-150 again.

Please see the report as below;

[Hardware Configuration]

The VBAT measured point is moved to the battery plug in.

[Test result]

1. In case the battery inserted inserted quickly

4174.tek00002.tif

CH1 shows the voltage level on VBAT with adding 4V offset, meanwhile CH2 shows the current level (forward direction into the battery). On this case, the charging into the battery is started properly.

4745.tek00003.tif

The charging into the battery is continuously done for few seconds.

2. In case the battery inserted slowly

1464.tek00004.tif

CH1 shows the voltage level on VBAT with adding 4V offset, meanwhile CH2 shows the current level (forward direction into the battery). On this case, the charging into the battery is not started properly.

7563.tek00005.tif

After this phenomenon, bq24250 never try to charge the battery again.

If you have any further information needed, please free to ask me.

We thank you once again for your information.

Best regards,

Hello Okui-san,

I noticed that the VBAT was probed at the end of the long wire after the meter, which will create some voltage drop over it. Can you place the voltage probe to TP2 of the EVM directly and capture the signal? Please also change the voltage scale to 100mV/div.

Besides, from the plots you attached, I still couldn't tell where is the point that the battery was plugged in - the battery voltage didn't have any change. I expect to see the voltage raising at the very beginning. And do you have any load on SYS pin?

Thanks,

Wenjia

Wenjia-san,

Thank you for your continuous support towards the inquiry regarding bq24250 from our customer.

In accordance with your requirement, I have measured the phenomenon on bq2425xEVM-150 once again.

[Hardware Configuration]

The VBAT measured point is moved to TP2 of the EVM. The point that the battery was plugged in was the left side of multimeter, which is described as RED circled.

There is "no load" after CS IN/SYS of J9.

[Test result]

1. In case the battery inserted quickly

1856.tek00010.tif

3146.tek00011.tif

2. In case the battery inserted slowly

4722.tek00012.tif

4338.tek00013.tif

* CH1 shows the voltage level on VBAT with adding 4V offset, meanwhile CH2 shows the current level (forward direction into the battery).

I hope this could help you to know the detailed behaviour.

We thank you once again for your confirmation.

Best regards,

Hello Okui-san,

The good news is I was able to re-create similar behavior with the bq24250 EVM. The bad news is why the IC was doing this is still not clear to me. 

Initially I was thinking there may be some transient in the battery voltage that caused the IC not charging and I was trying to link the battery voltage drop in your plot "tek00012" to the charging behavior. However, I did the experiment tens of times and in most of the cases, I didn't see the voltage drop and the IC still didn't start charging.

I will continue to check other possibilities and at the meanwhile, may I ask you if this has caused any issue in customer's application? What is the ideal case that the customer expects?

Thanks,

Wenjia

Wenjia-san, 

Thank you for your continuous support towards the inquiry regarding bq24250 from our customer.

With regard to your questions, actually they just would like to make sure whether this behaviour is based on the specification of this device or not.

They don't have any particular issue caused by this behaviour.

We are looking forward to hearing some additional information.

Best regards,