BQ25504: VBAT_OK

Nilson Yang

Part Number: BQ25504

Hi Sir,

Sorry about old question has been closed. I open new question for this topic.

We finally increased the CSTOR in system (CE1) to 470 uF. It seems resolved the question. However when we increased the charger power, it has failed.
In old question, we can not see VBAT traces VSTOR. That's why we were concerned about this question.

We used the 14500 800mAH Li ion rechargeable battery in this system, we cannot provide scope capture of the charger behavior when battery is more than 3.5V (VBAT_OK_HYST) to 4.22V (VBAT_OV).
The battery need 3 days to be recharged 0.1 Volt.

Our question still can be described as below picture.

Yello: +VSTOR

Blue: +VBAT (3.146V Li-On Battery)

Purple: VBAT_OK

When +VSTOR rises to VBAT_UV, the internal PMOS will be opened. The +VSTOR and +VBAT will be the same, right?
However our system will raises the VBAT_OK to open external PMOS. Does it seem that skip the charger mode?

over 5 years ago

0 Upal Patel over 5 years ago

TI__Intellectual 1640 points

Hello Nilson,
Can you please provide the updated application schematic?
It also seems like, you're trying to charge a large battery, and also large system load powered, with limited input power.
Can you also provide the VOC and ISC if you're using solar input?

0 Nilson Yang over 5 years ago in reply to Upal Patel

Prodigy 210 points

Hi Upal Patel,

We didn't use the solar power. We use the current transformer. I can not provide all the schematic in internet. But when system is in balance (if the VBAT_OK were not release earily), it can charge the battery from 3.1V to 3.5V in 1 week. The charger schematic is shown as below,

0 Upal Patel over 5 years ago in reply to Nilson Yang

TI__Intellectual 1640 points

Hello Nilson,
It seemed like, your issue was resolved with larger CSTOR cap with the original questions.
What's the charge power when you mentioned you increased it, and it failed? Thank you.

0 Nilson Yang over 5 years ago in reply to Upal Patel

Prodigy 210 points

Hi Upal Patel,

We used the Current Transformer to transfer the charge current to our system. CT is 1:3000.

When the Primary side has 10 A (110V AC), it can transfer 3mA to our system. And it works.

We just increase the Primary side Current to 20 A, the VBAT_OK still raise before +VSTOR.

Nilson

0 Upal Patel over 5 years ago in reply to Nilson Yang

TI__Intellectual 1640 points

Hello Nilson,

From your plot it scope capture it seems like VBAT_OK raises when VSTOR is about 3.49V, which when I refer to the calculations is correct since you programmed VBAT_OK_HYST at 3.49V. Please follow the diagram below:-

0 Nilson Yang over 5 years ago in reply to Upal Patel

Prodigy 210 points

Hi Upal Patel,

That will be "VBAT connected to VSTOR to allow charging" first, right? However, Bq25594 didn't connect VBAT and VSTOR and trigger the VBAT_OK.

Thanks.

Nilson

0 Upal Patel over 5 years ago in reply to Nilson Yang

TI__Intellectual 1640 points

Hello Nilson,

Would it be possible for you to send me a scope capture of VSTOR and VBAT from 1V to 3.14V? It seems like you've charged the battery to 3.14V, but your VBAT never reached VBAT_UV threshold, one of the reason I could think of is the large battery capacity (800mAh) you're using, and charging at 3mA, VSTOR always gets the preference as system is connected to VSTOR.

0 ezhao over 5 years ago in reply to Upal Patel

TI__Genius 10240 points

Nilson,

We haven’t heard back from you. We are assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.

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BQ25504: VBAT_OK