BQ40Z50EVM-561: Difficulties discharging cells

Andrew Lucas

Part Number: BQ40Z50EVM-561
Other Parts Discussed in Thread: BQ40Z50, BQSTUDIO

I am attempting to discharge a 12.6V 7500mAh battery pack using this board in preparation for a learning cycle. However, when I attach a low value resistor that would allow a C/10 discharge rate, the bq40z50 seems to go into a protective state disconnecting from bqstudio and closing the power FETS.

1. Is this due to a short circuit / overload protection being triggered?

2. What would be the best way to go about achieving a proper discharge with this board, such as settings I should change in bq40z50 to achieve a proper discharge?

over 1 year ago

0 Wyatt Keller over 1 year ago

TI__Guru** 102375 points

Hello Andrew,

Please review our FAQs about what data is needed to best help with debugging the gauge:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1100653/faq-impedance-track-faqs

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1100663/faq-what-information-does-ti-need-to-help-with-learning-accuracy-operation-related-questions

Please also share a screenshot of BQStudio after the issue occurs (make sure to refresh the registers first so any new bits are shown).

Sincerely,

Wyatt Keller

0 Andrew Lucas over 1 year ago in reply to Wyatt Keller

Prodigy 20 points

Here is a screenshot of bqstudio after the load is applied:

/resized-image/__size/1920x1080/__key/communityserver-discussions-components-files/196/bqstudio-post-error.png

/resized-image/__size/1920x1080/__key/communityserver-discussions-components-files/196/bqstudio-post-error-registers-pt2.png

I have no log files as this was noticed before I began a learning cycle.

0 Wyatt Keller over 1 year ago in reply to Andrew Lucas

TI__Guru** 102375 points

Hello Andrew,

The gauge should not shutdown just from applying a resistive load, even if the protections are triggered it should stay active. Are you able to recover by applying voltage on the PACK pin? How do you recover the gauge to normal conditions again? Can you capture the BAT and VCC waveforms when you attached the load?

Sincerely,

Wyatt Keller

0 Andrew Lucas over 1 year ago in reply to Wyatt Keller

Prodigy 20 points

I am able to recover by removing the load from the circuit and then pressing the "wake" button. once the board reconnects I have to re-open the FETS to repeat the error.

Am I able to capture the BAT & VCC pins through the data graph utility in BQstudio? I found the ability to record the BAT pin in the data graph menu but I could not figure out how to begin plotting data.

0 Wyatt Keller over 1 year ago in reply to Andrew Lucas

TI__Guru** 102375 points

Hello Andrew,

No, we would need oscilloscope captures to verify what is going on for these pins. If you have to apply the voltage on PACK pin to wakeup the device it means it lost power and went to shutdown.

Sincerely,

Wyatt Keller

0 Andrew Lucas over 1 year ago in reply to Wyatt Keller

Prodigy 20 points

I am able to wake the device by placing an external voltage across Pack+ and Pack-. Could the a voltage drop created by the load be a cause for the system to sleep or shutdown?

+1 Dominik Hartl11 over 1 year ago in reply to Andrew Lucas

TI__Guru 51366 points

Sleep would not cause this. It would have to be shutdown and yes, voltage can cause shutdown, depending on configuration. It could also be a brown-out. TI USA is on holiday today and Wyatt will likely not reply until Monday.

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BQ40Z50EVM-561: Difficulties discharging cells