BQ20Z655-R1: SOC drop to 0% at -40 temp and doesn't return

Ilia Mokrushin

Part Number: BQ20Z655-R1
Other Parts Discussed in Thread: GPCRB, BQ40Z50, BQ40Z50-R2

Hi all, i'm testing our battery pack of 4s10p 18650 bank. At extra low temperature (-40) SOC drops to 0%, and i know that i need to use GPCRB for using pack on low temperature, but i have no way to connect my laptop into temerature box. But i don't understand, why BQ shows 0% SOC, after our pack back to room temperature?

over 6 years ago

0 Batt over 6 years ago

TI__Mastermind 42535 points

Once you get back to 0C, you will have to wait in relaxation for 5 hours for capacity simulations to take place. The delta T simulations in the newer gauges take place every 5C. I suggest thatyou use a bq40z50 for your application.

0 Ilia Mokrushin over 6 years ago in reply to Batt

Prodigy 50 points

Hello. My pack was 2 days at room temp, but doesn't back to normal work.I can only exit this mode by connecting charge. After connect BQ show normal SOC.

0 Batt over 6 years ago in reply to Ilia Mokrushin

TI__Mastermind 42535 points

Do you have logs for it? This is a very old gauge, some of the algorithms for capacity estimation have changed in the way they function. If you can, I would suggest that you use the bq40z50-r2.

0 Ilia Mokrushin over 6 years ago in reply to Batt

Prodigy 50 points

I have 2 screenshots. 1 after get out from the box, and 2 after night in room temperature

After night:

bq20z655.zip

0 Batt over 6 years ago in reply to Ilia Mokrushin

TI__Mastermind 42535 points

You've sent me a partial gg file. Please upload a full gg file with the df exported. Also, I can see that your voltage is low (not really near terminate but close to it within 300mV of it). I can see that your FCC was resimulated by the gauge when the temperature change. However, based on your Ra values, it still thinks the resistance is high enough to cause RM to be 0. You may also want to change load select to 0, 1, or 3 to get better results.

0 Ilia Mokrushin over 6 years ago in reply to Batt

Prodigy 50 points

Thank you Batt, but i broke my BQ when flashing .dfi. When i repair that, I will try change load select, and upload logs. I have logs for another battery pack, 4sp1 with same batteries, and these pack dont have bug at -20 and shown normal RC and FCC18650_3500_green_vs_red.xls

0 Batt over 6 years ago in reply to Ilia Mokrushin

TI__Mastermind 42535 points

No two batteries, even from the same mfg and production line are the same. The internal resistance of some batteries is higher than others. That can lead to significant performance differences at extreme temperatures. It is unlikely that this is a fw issue.

0 Ilia Mokrushin over 6 years ago in reply to Batt

Prodigy 50 points

I found bit LOCK_0 on Data flash (Operation Cfg C), and turn off. My pack shows normal value after relax now. I think its resolve my issue

0 Batt over 6 years ago in reply to Ilia Mokrushin

TI__Mastermind 42535 points

Great. Thanks for posting it to help others here.

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BQ20Z655-R1: SOC drop to 0% at -40 temp and doesn't return