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BQ27741-G1: BQ27741EVM is not working

Esmaeel Heidari
Prodigy 30 points
Part Number: BQ27741-G1
Other Parts Discussed in Thread: BQ27741EVM, BQ26500, BQSTUDIO,

Hello everyone,


I bought a bq27741EVM  several months ago and try to run that and use it in a battery pack.

According to the user manual, I have done. but unfortunately, I was not successful in learning and exactly using the BQ27741.

I have done as like as this link:

https://blog.fearcat.in/a?ID=00550-5997a477-f62f-4dd2-88c2-5a06bdd00eff

 

Now I have 3 EVM. which behave in different ways

 

No1. Start charging, after about 2 hours the charge current comes down, and then it stops charging.

No2. Never start charging, just discharge

No3. Start charging but don't reach charge voltage (4.2V) just to 3.8 v

 

- battery type:

1- Sony-US18650VTC5A-36-Volt-2600mAh-Li-Ion

2 - muRata-US18650VTC6-36-Volt-3000mAh-Li-Ion

- charger type (constant current, constant voltage)

- settings

All parameters are default, but

Design Capacity: 2600

Design Energy: 2600*3,7

CHEM-ID: 2161

 

I have some log files from all 3.

Everyone that has some experience in this case,  Please help me.

Regards
Esmaeel Heidari

  • 0
    TI__Guru 62386 points

    What is the state of the DSG and CHG FETs? If both are on, then the gauge doesn't control when a battery stops or starts charging (the charger and the load control this, the gauge just measures passively).

    If the DSG and/or CHG FETs are off, then you need to check if the protection settings that you chose tripped due to a protection condition in your system.

  • 0 in reply to Dominik Hartl11
    Prodigy 30 points

    Hi Dominik


    Thanks For your response
    DSG and CHG FETs are not turned on together(Just one or 2 times before).


    Flags show you the state of the CHG and DSG
    I will send the Configuration and log data here:
    TimeStamp,                     Control,Control Status,Temperature,Voltage,Flags,Average Current,Internal Temperature,State Of Charge,Pack Configuration,
    2022-08-22 08:44:01.988,0x2161,0x001D,            27.7,              2985,0x0106, 0,                          25.0,                              0,                       0x0171,
    ...
    2022-08-22 08:45:22.215,0x0108,0x000B,            29.6,              3130,0x0186,689,                       26.7,                              1,                        0x0171,
    ...
    2022-08-22 09:02:29.661,0x0108,0x000B,            27.9,              3261,0x0186,100,                       25.1,                              7,                        0x0171,

    Dominik Hartl11 said:
    If both are on, then the gauge doesn't control when a battery stops or starts charging (the charger and the load control this, the gauge just measures passively).

    Would you explain more?

    thanks

    ...

    Charging Voltage 4200 mV
    Taper Current 100 mA
    Min Taper Capacity 25 mAh
    Taper Voltage 100 mV

    Design Voltage 3700 mV
    Initial Standby -10 mA
    Initial MaxLoad -500 mA
    CC Threshold 900 mAh
    Design Capacity 2600 mAh
    Design Energy 9620 mWh
    SOH Load I -400 mA
    Dsg Current Threshold 60 mA
    Chg Current Threshold 75 mA
    Quit Current 40 mA
    Dsg Relax Time 60 s
    Chg Relax Time 60 s
    Quit Relax Time 1 s
    Max IR Correct 400 mV
    Qmax Cell 0 1000 mAh
    Update Status 4 Num
    V at Chg Term 4200 mV
    Avg I Last Run -299 mA
    Avg P Last Run -1131 mA
    Delta Voltage 2 mV
    T Rise 50 Num
    T Time Constant 1000 Num
    Chem ID 2161 flags



  • 0 in reply to Esmaeel Heidari
    TI__Guru 62386 points

    What is the state of the protector (HW and FW) in your system?

    Esmaeel Heidari said:
    Would you explain more?

    The bq27741 is a gauge with a HW and FW protector. The gauge part is "just" a measuring device. It will not control any current so this will not affect when charging stops or when discharging stops.

    The protector part has the ability to control current because it controls two FETs, a discharge FET and a charge FET. The rules are complex and explained in the datasheet (HW protection, www.ti.com/.../slusbf2c.pdf) and the User's Guide (FW protection, www.ti.com/.../sluuaa3.pdf). The gauge reports the state of the protector with commands 4.2.10 Protector Status: 0x6D and 4.2.16 Protector State: 0x78.

    If the protector disables one or both FETs, it will affect the current in/out of the cell. Please check the "Operating Modes", figure 10 in the datasheet and 5.3.1.3 Overtemperature Protection Threshold, Delay Time, and Recovery in the User's Guide to make sure your system isn't entering a state where the bq27741 protector turns off one or both FETs. 

  • 0 in reply to Dominik Hartl11
    Prodigy 30 points

    I have checked all the logs, and these two registers are always constant, like this.

    Protector State: 0x02 --> Normal

    Protector Status : 0x00 -->  
    CHG_OFF = Firmware override to disable charge FET:
    1 = Charge FET Off

    0 = Charge FET On

    DSG_OFF = Firmware override to disable discharge FET:

    1 = Discharge FET Off

    0 = Discharge FET On

    That means I should change the Protector Status? or It is correct!!

    I have checked the 5.3.1.3 Overtemperature
    in all logs, the temperature is lower than 30°C

    thank you for your answers

  • 0 in reply to Esmaeel Heidari
    TI__Guru 62386 points

    So both FETs are always on then? In this case, the problem seems to be with the charging setup. Are you sure that the charger works correctly?

  • 0 in reply to Dominik Hartl11
    Prodigy 30 points

    In our last design, we used BQ26500 (without protection), I use the last charger that worked correctly with the last Gas Gauge.

    In this case, I have done:
    Connect the Hws as like as the manual (sluuah1.pdf)
    Turn on the charger

    Open the Bqstudio 1.3.101

    Config the Data Memory
    Design Capacity: 2600, Design Energy:9625, Chem ID: 2161,

    According to the Operating Modes (P.19) in the bq27741-g1 datasheet: ()
    Normal: CHG and DSG should be On, but that does not happen.

    I have read several Docs from TI but unfortunately, the normal operation of this gas gauge is unclear to me.
    How are they: hardware connections, necessary Configs, software, and then the results? (Just for a normal operation)

    I read the documents several times, but ...

  • 0 in reply to Esmaeel Heidari
    Prodigy 30 points

    One other thing
    When the charger is On:

    Batt voltage: 3.3v,

    Flags: CHG is set (red) and DSG is not set (green)
    but the Voltage of the
    CHG Pin is: 1.5 to 2 Volt
    DSG Pin is: 0.7 Volt

    a charge is not started anymore!!! (Level of the gate for CHG&DSG MOSFET should be about 6 volts)


  • 0 in reply to Esmaeel Heidari
    TI__Guru 62386 points

    CHG set means that the gauge allows fast charging. DSG not set means that the gauge hasn't detected a discharge. So this looks ok.

    Please run the FET test as described in the TRM and monitor the CHG and DSG pin to check if this actually works. If not, the gauge may be damaged.

  • 0 in reply to Dominik Hartl11
    Prodigy 30 points

    Yes, you are right. One of the Gas gauges is damaged.

    I have seen that: "The fuel gauge resides within the battery pack or on the system’s main board with an embedded battery (non-removable)."
    I have tried the new Gas gauge with the new situation.

    I have used:
    a 5300mAh Li-ion battery (Boston Power, Swing 5300)
    change the Design Capacity, Design Energy, SOC1 Set thr, SOC1 Clear, SOCF Set, SOCF Clear, CHEM ID,

    I suppose that it should charge when I turn on the charger and Start discharging when I connect the load (10 Ohm). 
    When I used the load it was working (CHG and DSG pin was 6 volts) when BAT voltage reach 3 volts the protector disconnect the load.
    After about 5 hours, I turned on the charger and remove the load from the circuit but the charge is not started (  (CHG pin was 6 volts but DSG is below 1 volt)

    I am confused
    I expect that it should work in this state!!!!!

  • 0 in reply to Esmaeel Heidari
    TI__Guru 62386 points

    The system (gauge + DSG and CHG FETs + charger + cell etc.) will still charge if the charger really turns on if the CHG FET is still on. It doesn't matter, if the DSG FET is off because the DSG FET is only off in one direction (discharge) but it has a body diode in the charge direction and as long as the CHG FET is on, even if the DSG pin is below 1V, there is a path for the charging current from the charger to the cell through the DSG FET body diode and the conducting CHG FET (with CHG pin = 6V). The gauge will detect that there's a charging current through the sense resistor and if this is above the CHG current threshold, it will turn on the DSG FET to protect the body diode.

    Are you sure that your charger is actually on? If so, then there will be a charging current into the battery if CHG pin = 6V.