bq24773: bq24773 charging Issue.

Chun Youngsu

Part Number: BQ24773

Dear TI Team.

I have a problem designing the bq24773 question.

In order to check whether or not the battery is installed, we designed to check the Inhit bit and Charging Current every 1 second.

During testing using the 2S battery, the battery will be intermittently recharged from the battery of less than 5.2V during the repeated test of detaching and attaching the battery.

If you remove the check function by changing the Inhit bit and Charging Current once per second, the symptoms disappear.

Could you tell me why?

And if there is any other solution that can check the detachment / attachment of the battery, please recommend it.

Thanks.

over 7 years ago

0 Wang5577 over 7 years ago

TI__Guru 56650 points

“The battery will be intermittently recharged from the battery of less than 5.2V during the repeated test of detaching and attaching the battery.”

If the battery is absent, please disable charge. If not, you are going to see this because charger doesn’t know the battery is there and push a small current into BAT output. That small current is higher enough to drive output trigger OVP and BATET off.

Does the battery pack have battery present pin? Can you design the battery pack terminal and let the host controller know the battery plug-in?

0 Chun Youngsu over 7 years ago in reply to Wang5577

Expert 2485 points

Dear Wang,

It seems that the content delivery is wrong.

We have implemented S / W to recognize when there is no battery by changing the Inhit bit and Charging current to determine whether the battery is present or not.
If the battery is detached / attached due to the symptoms that occur after that, the phenomenon that the battery can not be charged occurs intermittently.
Symptoms can occur with a battery whose battery voltage is 5.2 V or less.
Symptom can be improved by removing the implemented S / W to determine the battery's presence / absence. Can you tell me why?
And can you identify other solutions that can confirm battery removal / attachment?

Thanks.

0 Wang5577 over 7 years ago in reply to Chun Youngsu

TI__Guru 56650 points

1. Please send out the "symptom" waveform to show abnormal signal.

2. Can you disable the auto wake-up bit and compare the difference?

0 Chun Youngsu over 7 years ago in reply to Wang5577

Expert 2485 points

Dear Wang,

The picture below is the register value we set.

We change the two parts shown on the picture every second to confirm the removal / attachment of the battery.

If this happens, the part that can not be charged occurs.

Symptoms can not be reproduced if the register value is not changed every 1 second.

We need to check Plug and unplug the battery.

If the battery is fully charged and fully discharged, check the battery plug and unplug.

Charging setting

Discharging Setting

0 Wang5577 over 7 years ago in reply to Chun Youngsu

TI__Guru 56650 points

"Symptoms can not be reproduced if the register value is not changed every 1 second." What symptoms? Can you show me the waveform?

0 Chun Youngsu over 7 years ago in reply to Wang5577

Expert 2485 points

Dear Wang5577,

Sorry for late reply.

In order to check the plug and unplug of the battery, we change 0bit of 0X00 and 7bit of 0X0A of Addres every 1 second.
The image below shows the waveform of the BAT connection point when the battery is present and when there is no battery.

When the above-mentioned function is implemented by MCU, it often happens that the battery can not be charged when the battery is less than 5.2V. Is it possible to see what is wrong?

0 Wang5577 over 7 years ago in reply to Chun Youngsu

TI__Guru 56650 points

bq24773 doesn't have battery detection function. It seems you want to enable charge or disable charge to help MCU or host controller to do the battery detection. The host can disable or enable charge if they want. But, I don't know how the host can detect battery by doing it?

"When the above-mentioned function is implemented by MCU, it often happens that the battery can not be charged when the battery is less than 5.2V. "
Please don't use that method to that battery detection: a. I still don't understand how it works (if the setting voltage is same as the battery voltage, how can you detect it?) b. As you said, the battery cannot be charged ( I don't have the detail from you, such as cannot be charged due to converter latch-off? how do you resume charge? Or, the charge voltage setting is lower than battery voltage? Or, the battery voltage is lower than the minimum system voltage?)

0 Chun Youngsu over 7 years ago in reply to Wang5577

Expert 2485 points

Dear Wang5577,

Sorry for the delay.

1. Check battery status every 400ms and set charging current / voltage with I2C.
2. If the battery voltage reaches the maximum charge voltage and the charge current is 0,
- Blocking method: Charging current 0 mA setting & Charge Inhibit setting & charging voltage 8.4 V setting. (Other setting values are not changed.)
3. Charging starts when the battery voltage is 0 mV.
- Charging method: Charging current 128 mA setting & Charging voltage 8.4 V setting & Charge Inhibit disarming. (Other setting values are not changed.)

This is the method implemented by the MCU to verify battery disconnection.

In the above method, as mentioned above, there was an intermittent charging problem.

I want to know if there is another way to check the battery removal.

Thanks.

Power management

Power management forum

bq24773: bq24773 charging Issue.