BQ27426EVM-738: BQ27426 SoC Reading Issue during Discharging cycle

Sahil Nayak

Part Number: BQ27426EVM-738
Other Parts Discussed in Thread: BQ27426, BQ24192, BQSTUDIO, EV2400

Hi TI Team,

In our product for monitoring the battery we have used bq27426EVM-738 EVK and for charging the battery we have used bq24192EVM-021.

Both are connected with the STM32L5.

Setup information:

1. Fuel Gauge EVK

BQ27426 FG EVK	Connections
Load+ (J6)	BAT pin of BQ24192 charger chip EVK(J2.1)
Load- (J7)	GND of BQ24192 charger chip EVK (J2.3)
Pack+ (J5.1)	Battery +ve
GPOUT (J2.2)	GPIO of STM32 EVK
BIN (J5.2)	NTC pin of Battery
Pack- (J5.3)	Battery -ve
SCL (J1.2)	SCL (J3.9) of BQ24192 charger chip EVK
SDA (J1.3)	SDA (J3.10) of BQ24192 charger chip EVK

2. Charger chip EVK

BQ24192 Charger Chip EVK	Connections
PG (TP5)	GPIO Pin of STM32EVK
STAT (TP10)	GPIO Pin of STM32 EVK
SCL (J3.9)	I2C SCL of STM32 EVK
SDA (J3.10)	I2C SDA of STM32 EVK
INT (J4.4)	GPIO Pin of STM32 EVK
CE (J4.2)	GPIO Pin of STM32 EVK
BAT (J2.1)	Load+ (J6) of BQ27426 FG EVK
VBUS (J1.2) GND (J1.1)	DC Jack GPB

Using this setup we have received the battery voltage, battery current and SoC value of battery successfully in STM32.

Observation:

1. When we charge the battery using charger chip EVK then SOC % gets updated accordingly.

2. When we discharge the battery using DC ELECTRONIC LOAD then the voltage is decreasing but SOC% remains stuck at one value (doesn't update in runtime).

For debugging purpose, I have checked the flag register and I received below values:

Flags Register:

	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
High Byte	OT	UT	RSVD	RSVD	RSVD	RSVD	FC	CHG
Low Byte	OCVTAKEN	DOD CORRECT	ITPOR	CFGUPMODE	BAT_DET	SOC1	SOCF	DSG

Received 16 bit value : 0x1C8

1. Now the question is why the DSG bit is zero when I put the system in the discharging mode.

Please help me to resolve this issue.

Note: We have used 5000 mAH battery capacity and we have set the CHEM_ID as Profile B as per battery specifications.

over 5 years ago

0 Wyatt Keller over 5 years ago

TI__Guru** 106615 points

Hello Sahil,

Can you use the EV2400 and BQStudio to log the data and pull the .gg file from the gauge? This is the easiest way to debug for us.

There are certain modes on the gauge to hold the SOC if the conditions are met: SOCHoldOvrChg or SOCHold99, you can check this from the .gg file. If the DSG bit isn't setting the threshold may have been changed, that is also viewable in the .gg file.

Sincerely,

Wyatt Keller

0 Sahil Nayak over 5 years ago in reply to Wyatt Keller

Intellectual 450 points

Hi Wyatt,

Thank you for your quick response.

Please find the attached .gg file which we have generated from bqstudio.

We also observed that in bqstudio too, the SoC value was not updating.

Please provide the solution for this.Final Gas gauge.gg.csv

0 Wyatt Keller over 5 years ago in reply to Sahil Nayak

TI__Guru** 106615 points

Hello Sahil,

Turn off the SOC hold functions in opconfigC to see if the issue is resolved. If the DSG bit is not being set you may need to change the Dsg Current Threshold so the gauge knows when you are discharging for your applications expected load.

Check section 7.4.2.2 of the TRM:

www.ti.com/.../sluubb0.pdf

Sincerely,

Wyatt Keller

0 Sahil Nayak over 5 years ago in reply to Wyatt Keller

Intellectual 450 points

Hi Wyatt,

We tried out both the solutions suggested by you but still we aren't able to detect discharging.

We also observed that in bqstudio Average Current value is always zero while discharging cycle.

Please find the attached .gg files for both solutions as suggested by you.

GGFILE_SOC_HOLD_DISABLE.gg.csv GGFILE_DSG_CURRENT_THRESHOLD.gg.csv

0 Kang Kang over 5 years ago in reply to Sahil Nayak

TI__Mastermind 24870 points

Hello Sahil,

Make sure that the load current is going through the sense resistor and you have it hooked on the EVM the same as the EVM user's guide.

Thanks

Power management

Power management forum

BQ27426EVM-738: BQ27426 SoC Reading Issue during Discharging cycle