BQ27220: Abrupt change in reading received from the BQ27220 gauge read routine.

Darpan Noel DSouza

Part Number: BQ27220

Hi,

I have created this golden image for the battery monitoring (please find attachment) for my device which is supposed to work for prolonged period with a battery percentage feature. While testing I noticed that the Battery percentage reading that I get from the configured gauge drops by many values from 24 % to 7% in one of the examples I have monitored.

Please could you help me out as to what I have done wrong and how I can correct it.

The following is the reading that my device reads from the gauge every 5 minutes.

[2020-02-19 10:37:23.527] [I] GAUGE READ SUCCESS: 24 Percent 3610 mV 0 mA 23C
[2020-02-19 10:42:23.183] [I] GAUGE READ SUCCESS: 7 Percent 3609 mV -5 mA 23C
[2020-02-19 10:47:23.235] [I] GAUGE READ SUCCESS: 7 Percent 3609 mV -5 mA 22C
[2020-02-19 10:52:23.280] [I] GAUGE READ SUCCESS: 7 Percent 3609 mV -6 mA 22C
[2020-02-19 10:57:23.327] [I] GAUGE READ SUCCESS: 7 Percent 3595 mV -394 mA 22C

[The attached file was with a .fs extention, in order to upload I changed it to .zip. Please change the extension as you prefer]

Regards,

Noel.

0220_0_03-bq27220_golden_image_after_3percent.gm.zip

over 5 years ago

0 Andy Liu (BMS) over 5 years ago

TI__Guru 52115 points

Hi Noel,

Can you provide a bqSutdio log file? Thanks.

Andy

0 Darpan Noel DSouza over 5 years ago in reply to Andy Liu (BMS)

Intellectual 685 points

Hi Andy,

I am unable to connect the gauge with the evm board to monitor the battery drain since the gauge is already a part of my devices and I cannot manage to interface it now.

Is there anything else that I can do in order to get a clearer picture of the situation?

The battery percentage drops drastically without there being a similar drop in the voltage.

Regards,

Noel.

0 Darpan Noel DSouza over 5 years ago in reply to Darpan Noel DSouza

Intellectual 685 points

Hi,

Any developments on this issue?

I have a log file created from the BQ studio for the same device. I am not sure if it is what you are asking for. Please have a look at it and let me know.

Regards,

Noel.

discharge_logs_battery_pack_after_3percent.log

0 Kang Kang over 5 years ago in reply to Darpan Noel DSouza

TI__Mastermind 24870 points

Hello Darpan,

What you are showing is normal behavior for the CEDV gauge. When you have a high current coming in and it hits EDV2, we will always jump to 7% SOC.

0 Darpan Noel DSouza over 5 years ago in reply to Kang Kang

Intellectual 685 points

Hi Kang,

Yes when I monitored my device logs I did notice that there was a lot of processes that were on during that interval and there is a possibility of a lot of current being used from the battery and the voltage must have momentarily dropped to the CEDV value, but afterwards the voltage stabilized.

If we reset the gauge during this situation it should give us a proper reading back again, right? Is there any harm in doing this?

Or what if we set the CEDV value extremely low, will it cause an issue?

Regards,

Darpan.

0 Kang Kang over 5 years ago in reply to Darpan Noel DSouza

TI__Mastermind 24870 points

Hello Darpan,

You can set it but only in EDV mode and not CEDV mode. CEDV mode means EDV2 is computed based on your terminate voltage and log files. You can set EDV0 low. That may help, but in general that is the "sync" point of EDV based gauges.

0 Jitendra Singh7 over 5 years ago in reply to Kang Kang

Expert 1435 points

Can you provide more details on below params:

EDV 0 Hold Time, EDV 1 Hold Time, EDV 2 Hold Time.

Regards

0 Dominik Hartl11 over 5 years ago in reply to Jitendra Singh7

TI__Guru 60916 points

The hold times control how long the measured cell voltage has to be below the EDVx threshold for the gauge to react (e.g. adjust SOC). By default it is <= 1 second.

This is intended to handle short current spikes that won't cause a problem with the system (e.g. brown out) but aren't indicative of a real reduction of capacity.

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BQ27220: Abrupt change in reading received from the BQ27220 gauge read routine.