BQ76PL455A-Q1: Linear & Step by Step

Aaron Lee21

Intellectual 300 points

Part Number: BQ76PL455A-Q1

Hi,

We are using BQ76PL455A-Q1 *2 for 26 series cell. The chart below shows the voltage(26 cells) of charging.

Why are some cells with a linear voltage, some of which are step-by-step?

over 6 years ago

0 Andy Li55 over 6 years ago

TI__Intellectual 2520 points

Hi Aaron,

Can you change the position of cells to see the symptom follows cells or follows channels?

Thanks!

Andy

0 Aaron Lee21 over 6 years ago in reply to Andy Li55

Intellectual 300 points

Hi Andy,

No. Because the battery pack use 9P26S (234 cells) and soldered together. They are difficult to separate.

Do you think it is feasible to test it with 26-serial of resistor and a 96V power supply?

1/4W 1Kohm * 26pcs

Do you have any recommend?

Best Regards,

Aaron

0 Roger Hwang over 6 years ago in reply to Aaron Lee21

TI__Genius 10785 points

Hi Aaron,

Where did you get the waveform?

Is it from scope or is it MCU measurement?

It seems to me that you are plotting measurements.

Is there waveform from cell side? If not then please capture the waveform on cell side.

thanks

Roger

0 Aaron Lee21 over 6 years ago in reply to Roger Hwang

Intellectual 300 points

Hi Roger,

It is from the MCU.

What instrument do you prefer to measure the voltage of cell side? We have multi-meter and 2 channels oscillator-scope.

Best Regards,

Aaron

0 Roger Hwang over 6 years ago in reply to Aaron Lee21

TI__Genius 10785 points

Hi Aaron,

We have to determine whether plot is real or not.

Are you charging or discharging when you are plotting?

The best way is use scope, not a meter, and see whether you see same waveforms.

Remember, there is a RC filter so you won't get the exact same waveform but you can see the pattern.

Another waveform you need check is after RC filter. This waveform should match your MCU waveform.

Am I making sense?

Once you have two waveforms then you can determine whether you have proper RC filter or not.

You can share the waveform then we can help you with the RC filter.

Another option is digital filtering. It means that MCU read multiple readings and do average.

It's okay in noise environments.

Roger

0 Aaron Lee21 over 6 years ago in reply to Roger Hwang

Intellectual 300 points

Hi Roger,

We are charging when we are plotting. The MCU read voltage of 26-cell from BQ76PL455A-Q1, then transmit to PC using UART to USB cable.

You can see the purple line & green line are different in my plot. The purple line step by 1mV. The green line step by 20mV. Why?

The board and battery are not in here. We can not measure the cell-side now.

Best Regards,

Aaron

0 Aaron Lee21 over 6 years ago in reply to Aaron Lee21

Intellectual 300 points

Hi Roger,

You can see photo of our system in e2e.ti.com/.../792147

Best Regards,

Aaron

0 Roger Hwang over 6 years ago in reply to Aaron Lee21

TI__Genius 10785 points

Hi Aaron,

I saw the picture but I need to see the waveform from the scope.
Have you confirm with probe?

We need to know this before we can move on to next step.

roger

0 Aaron Lee21 over 6 years ago in reply to Roger Hwang

Intellectual 300 points

Hi Roger,

We are waiting for the board back to Taiwan. I will update the information when i get the waveform.

Best regards,

Aaron

0 Roger Hwang over 6 years ago in reply to Aaron Lee21

TI__Genius 10785 points

HI Aaron,

I am going to close this tread for now.

Please open new one if you still see problems.

thanks

ROger

Power management

Power management forum

BQ76PL455A-Q1: Linear & Step by Step