BQ34Z100-G1: Battery protection circuit getting triggered

SIDDHARTH ROY

Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ24170, BQSTUDIO, BQ34Z100

Hi,

I am facing an issue with my battery pack. The battery pack BMS is designed with BQ34gz100 fuel gauge. When the battery pack is plugged to be PCBA, sometimes( for example 10 out of 50 times), the protection circuit of the pack gets activated and I can see only 0.8V on my PCBA. The battery is 3S Li-ion battery(12.6V full charge voltage). To come out of this situation, I need to connect the DC charging adaptor. Once the battery comes out of this situation, it doesn't goes into the protection mode again. So this issue happens only sometimes while plugging the battery .

You can download my Power supply design schematic from the below link: It contains the overall all power architecture block diagram and power related schematic sections.

https://we.tl/t-vqqji4Fsdy

I am summarizing the power flow as below:

1, Battery is plugged at the connector J36(Page 1).

2. The charging IC BQ24170 detects valid battery voltage and turns the Q14 Mosfet. So the battery voltage VBAT becomes my main system voltage VSYS.

3. Now Vsys goes to input of U41 where it converts it to a 3V3 standby supply. Subsequently U9 is also turned ON.(Page 2)

4. Once , the U18 is turned using the button press event externally, the 5V and 3V3 regulators U15 ,U17 turns on on.

So, by just connecting the battery, only the First 3 points comes into picture. I would like to know whether there is anything suspicious which can take battery into the protected mode.

I have explored the facts like over/under voltage, Over current, short circuit and over temperature, But I feel all these 4 conditions doesn't comes into picture just by plugging the battery pack.

On the battery side, I do not have the design files for the BMS, but what I have checked with my supplier is , they have increased the peak current limits up to 10A from 2-3A. but still this issue is coming.

So, I would like to know whether is there anything on my PCBA which can create this problem?

For I2C lines, they are connected to my MCU but the pull-up voltage only comes after U17 is ON which after pressing the external ON/OFF switch.

Looking forward for your reply.

Thanks,

Siddharth

over 4 years ago

0 Nick Brylski over 4 years ago

TI__Mastermind 19195 points

Hi Siddharth,

Please upload the files here, I'm unable to reach the site you linked.

Thanks,

0 SIDDHARTH ROY over 4 years ago in reply to Nick Brylski

Intellectual 510 points

Hello,

Please find the attached files. Sorry for the incovenience.

Thanks,

Siddharth

Power_Supply-Design.pdf

0 Nick Brylski over 4 years ago in reply to SIDDHARTH ROY

TI__Mastermind 19195 points

Hi Siddharth,

What are the cell voltages in this case? Can you upload your .gg and logs showing the behavior.

Thanks,

0 SIDDHARTH ROY over 4 years ago in reply to Nick Brylski

Intellectual 510 points

Hi Nick,

The batteries are not fully charged. So the measured voltage is around 10.7V fir some of the packs. I have few packs which are having voltage around 11.2-11.4V.

The cell voltage shall be just divided by 3 as my battery pack is in 3s configuration.

Sorry, I do not have any log files with me.I need to check with my battery supplier.

My intention of raising this ticket is to get an idea of something looks suspicious on my pcba which can cause the battery pack to go in protection mode.

As far as I understand, there are 5 reasons which can trigger the protection circuit. Overvoltage,Undervoltage, Overcurrent,Short circuit and over temperature.

My gut feeling is only Overcurrent can be the reason in my case.There could be some inrush current because of capacitors on the VBAT line. But since the peak current limit is set at 10A, I cannot imagine how the issue still occurs.Even 10A is very big number looking at my circuit.

Let me know your opinion.

Thanks,

Siddharth

0 Nick Brylski over 4 years ago in reply to SIDDHARTH ROY

TI__Mastermind 19195 points

Hi Siddharth,

The .gg and logs can be generated from bq studio. Also some waveforms would be good to look at.

Thanks,

0 SIDDHARTH ROY over 4 years ago in reply to Nick Brylski

Intellectual 510 points

Hi Nick,

Sorry for the late response. I was busy with some other works.

How the battery shall be interfaced with BQStudio? Can you explain me a bit?

For wavfeorms, as of now I do not have much. I am planning to put a small series resistor in place of the fuse and my plan is to see the drop which will give me an idea about the inrush current. So I will update you on that once I do the experiment.

Thanks,

Siddharth

0 Nick Brylski over 4 years ago in reply to SIDDHARTH ROY

TI__Mastermind 19195 points

Hi Siddharth,

The .gg and logs can tell us about the status of gauge for debug. Or if you can obtain voltage readings or waveforms that would be helpful.

Best regards,

0 SIDDHARTH ROY over 4 years ago in reply to Nick Brylski

Intellectual 510 points

Hi Nick,

Finally I have some waveforms for you.

I put a 0.5E resistor in place of the fuse and tried to measure the drop across that while plugging the battery to my PCB. Attach is the waveform. The peak is going up to ~6V.By Ohm's lay if I calculate the current, it will ~12A. That is why even after increasing the peak current limit to 10A on the battery side, it is still going into the protection mode.

Peak voltage across 0.5E resistor:

Although I still not able to locate what is exact source of this peak current. I tried removing C273,C270 and C254 to reduce some capacitance. But there is no major change in the peak current. It is still close to 10A.

I also tried to see the Q14 gate voltage turn on time. It is 194us. So I do not think fast turning of the mosfet is the issue here. Attach is the waveform for that as well.

May be looking into these, you can let me know what else I can check.

Mosfet gate waveform:

Thanks,

Siddharth

0 Nick Brylski over 4 years ago in reply to SIDDHARTH ROY

TI__Mastermind 19195 points

Hi SIddharth,

Can you try upload the images again:

https://e2e.ti.com/support/site-support/f/1024/t/761613

Thanks,

0 SIDDHARTH ROY over 4 years ago in reply to Nick Brylski

Intellectual 510 points

AWaveforms Attached.8168.waveforms.docx

0 Nick Brylski over 4 years ago in reply to SIDDHARTH ROY

TI__Mastermind 19195 points

Hi Siddharth,

We will need the .gg and bqstudio logs to take this further.

Thanks,

0 Wyatt Keller over 4 years ago in reply to Nick Brylski

TI__Guru** 105590 points

Hello Siddharth,

Is this a gauge related question? It looks like the pack protections are triggering and causing the issue, we wouldn't be able to assist with this because the bq34z100 does not offer any protections.

Sincerely,

Wyatt Keller

Power management

Power management forum

BQ34Z100-G1: Battery protection circuit getting triggered