BQ78Z100: BQ78Z100 failing to terminate charge.

Timothy Vermilyea

Part Number: BQ78Z100

I'm experiencing an issue where my BQ78Z100 is failing to set the BatteryStatus()[FC] and BatteryStatus()[TC] flags after valid charge termination. This is in a 2S1P pack using 3400mAh cells charging to 8.4V. The charge termination current is 180mA, and the AverageCurrent() reading goes well below this in our logs. The total pack voltage usually reads around 8.37V around the time charge termination should happen. Our SOC Flag Config A is 0x0CAC, indicating that our ChargingStatus()[VCT] bit should set the FC and TC bits upon charge termination. Why would the BQ78Z100 fail to terminate the charge if all the conditions seem to be met?

over 5 years ago

0 Wyatt Keller over 5 years ago

TI__Guru** 105770 points

Hello Timothy,

Can you export the .gg file of the configuration so we can check the configuration of the gauge? If you have any logs as well that would be helpful for us to check as well.

Sincerely,

Wyatt Keller

0 Timothy Vermilyea over 5 years ago in reply to Wyatt Keller

Prodigy 60 points

Charge_Log.xlsx

0 Timothy Vermilyea over 5 years ago in reply to Wyatt Keller

Prodigy 60 points

0841.Golden_Image_Rev16.gg.csv

0 Wyatt Keller over 5 years ago in reply to Timothy Vermilyea

TI__Guru** 105770 points

Hello Timothy,

It looks like from your .gg file that your voltage thresholds are too high to set the FC condition, FC is set at 4250mV in your .gg file but your max cell voltage never reaches this value.

Make sure you are reaching all the conditions in section 4.6 of the TRM: https://www.ti.com/lit/ug/sluub63a/sluub63a.pdf?ts=1596492918104&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ78Z100

Sincerely,

Wyatt Keller

0 Timothy Vermilyea over 5 years ago in reply to Wyatt Keller

Prodigy 60 points

Hi Wyatt,

Thanks for your reply. I see that the FC Set Voltage Threshold is set to 4250mV. However, our application uses only the valid charge termination flag in ChargingStatus() to determine charge termination, we don't use cell voltage. In SOC Flag Config B, set to 0xAC, the FCSETV bit is not set, indicating that we are not using the FC Set Voltage Threshold to determine charge termination, but rather we are using the process described in section 4.6 like you mentioned. To clarify further, we are not using RSOC to determine VCT either (FCSETRSOC bit in SOC Flag Config B). All of the conditions for VCT are satisfied under our test cases, yet the ChargingStatus()[VCT] bit is not set. Any other suggestions? Much appreciated. Thanks!

0 Wyatt Keller over 5 years ago in reply to Timothy Vermilyea

TI__Guru** 105770 points

Hello Timothy,

I looked through your logs again and that's correct, it should be set with a VCT and it looks like all the conditions are met.

Can you share a log with all the registers so we can check to see if any other functions are interfering? Also make sure you have the most updated firmware, if this is a firmware issue it may be fixed in the most recent update.

Sincerely,

Wyatt Keller

0 Timothy Vermilyea over 5 years ago in reply to Wyatt Keller

Prodigy 60 points

I might be able to get the logs from the other registers, but it will take time, as the current log is produced using one of our products, and acquiring additional log data requires firmware updates to the entire system. The firmware should be up to date. We have 3 other types of packs in different configurations and some using different cells using the same gauge with no issues. The GG settings on these packs are mostly the same, with only minor differences.

0 Wyatt Keller over 5 years ago in reply to Timothy Vermilyea

TI__Guru** 105770 points

Hello Timothy,

The other registers will help us to determine the cause. What are the differences in the .gg files for the packs that are working? This may be a starting point for debug. How was the chemistry ID chosen?

Sincerely,

Wyatt Keller

0 Timothy Vermilyea over 5 years ago in reply to Wyatt Keller

Prodigy 60 points

Hi Wyatt,

It turns out we had programmed the Chem ID incorrectly. The issue has been resolved, thanks!

0 Wyatt Keller over 5 years ago in reply to Timothy Vermilyea

TI__Guru** 105770 points

Hello Timothy,

Glad to hear that you got it working! Let us know if you have any other troubles.

Sincerely,

Wyatt Keller

Power management

Power management forum

BQ78Z100: BQ78Z100 failing to terminate charge.