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BQ24296: Not Charging Batteries

Andrew Keller
Prodigy 140 points
Part Number: BQ24296

I am facing a major issue with the bq24296 that is the last remaining issue on my circuit.

I plug the battery charger in the batteries that are attached are not charging. I believe this only happens when the battery voltage drops below the VBATSYS of 3.5V. 

The register values of the chip are:

root@997eb9f:~# cat /sys/devices/platform/i2c\@9/i2c-9/9-006b/battparam 

reg 00 value    37

reg 01 value    1f

reg 02 value    60

reg 03 value    00

reg 04 value    b2

reg 05 value    8c

reg 06 value    73

reg 07 value    4b

reg 08 value    85

reg 09 value    02

reg 10 value    20

How do I get the charger to start charging the batteries if they are below this threshold?

Thanks,

AJ

  • 0
    Prodigy 140 points
    I also tried using a battery whose voltage is 3.66V and the battery charger was not working and the register values were:

    root@997eb9f:~# cat /sys/devices/platform/i2c\@9/i2c-9/9-006b/battparam
    reg 00 value 37
    reg 01 value 1f
    reg 02 value 60
    reg 03 value 00
    reg 04 value b2
    reg 05 value 8c
    reg 06 value 73
    reg 07 value 4b
    reg 08 value 85
    reg 09 value 82
    reg 10 value 20
  • 0 in reply to Andrew Keller
    Prodigy 140 points
    I read the register values again as the datasheet says to clear the faults and had:
    cat /sys/devices/platform/i2c\@9/i2c-9/9-006b/battparam
    reg 00 value 37
    reg 01 value 1f
    reg 02 value 60
    reg 03 value 00
    reg 04 value b2
    reg 05 value 8c
    reg 06 value 73
    reg 07 value 4b
    reg 08 value 85
    reg 09 value 02
    reg 10 value 20
  • 0 in reply to Andrew Keller
    Prodigy 140 points
    When I use a battery with 3.85V, the registers are a bit different:

    root@997eb9f:/usr/src/app# cat /sys/devices/platform/i2c\@9/i2c-9/9-006b/battparam
    reg 00 value 37
    reg 01 value 1f
    reg 02 value 60
    reg 03 value 00
    reg 04 value b2
    reg 05 value 8c
    reg 06 value 73
    reg 07 value 4b
    reg 08 value 84
    reg 09 value 02
    reg 10 value 20

    Which according to reg08 shows that we are not in VSYSMIN regulation, there is a good adaptor port.

    The problem I see is that register 07 is indicating a CHRG_FAULT and a BAT_FAULT.

    Any ideas?
  • 0 in reply to Andrew Keller
    TI__Mastermind 25800 points
    Hey Andrew,

    There is a TS fault present in all of your register readings. This means the voltage at the TS pin is not within the specified "normal" range, which makes the charger think that the battery is too hot. Charging stops here.

    I would check your resistor network on the TS pin and make sure the voltage on that pin, as a %REGN voltage, is between the VLTF and VHTF thresholds as specified in the EC table.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 140 points

    Joel,

    Thank you very much for pointing this out. I do not have a thermistor on the board.

    Please see the schematic below. I have a volatge divider, I got this circuit from the Artik Platform board.

    As you can see they use a regular 10k resistor. My plan right now is to remove that 10k resistor in place of a 10k thermistor.

    I have since ordered some thermistors from Digikey.

    Will this work?

    Thanks,

    AJ

  • 0 in reply to Andrew Keller
    TI__Mastermind 25800 points
    Hey AJ,

    We do not recommend just a single 10k thermistor to ground. I'm going to refer you to both Figure 17. TS Resistor Network and Figure 18. TS Pin Thermistor Sense Thresholds in Charge Mode of the datasheet for the proper reference for the TS pin configuration. The TS pin should be a percentage of the REGN voltage, as spec'ed in the EC table of the datasheet.

    If the TS voltage falls outside of certain percentages, it will flag the charger with a TS_COLD or TS_HOT flag. You can refer to the end of section 9.3.3.3 Thermistor Qualification for the standard values we use based on an 103AT NTC thermistor with Beta_25/85 = 3434


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 140 points

    Joel,

    I'm still having a strange issue with this chip. 

    The TS line appears to be indicating a fault:

    root@e4b620b:~# cat /sys/devices/platform/i2c\@9/i2c-9/9-006b/battparam 

    reg 00 value    37

    reg 01 value    0f

    reg 02 value    60

    reg 03 value    00

    reg 04 value    b2

    reg 05 value    8c

    reg 06 value    73

    reg 07 value    4b

    reg 08 value    84

    reg 09 value    01

    reg 10 value    20

    I see that because reg 09 is indicating a hot fault. 

    However! I can check the voltages and REGN is 5.08, and the TS pin is at 2.58V. 

    The specifications indicate that my V_HTF should be 2.39 with this RGEN value so why is this fault being triggered?

    My calculations are:

    Name Voltage (V) Notes
    RGEN 5.08
    V_LTF 3.7338
    Cold temperature threshold, TS pin voltage rising threshold. 73.5% REGN
    V_HTF 2.39776
    Hot temperature TS pin voltage rising threshold. 47.2% REGN
    V_TCO 2.27076
    Cut-off temperature TS pin voltage falling threshold. 44.7% of REGN

    The circuit on TS pin is now:

    It's worth noting that when the device is off, there are no charging issues, but then i can't really tell if it's the battery driver or the TS pin heating up.

    Thanks,

    AJ

  • 0 in reply to Andrew Keller
    TI__Mastermind 25800 points
    Hey AJ,

    This may sounds trivial, but are you measuring the REGN voltage and TS voltage directly at the pin?

    If this is true, then we may need to look to see if anything is happening transiently on an oscilloscope. You will want to put your probes on REGN and TS to see if any oscillation is occuring. We will also want to look at the charging current if possible on the same scope capture and/or /INT pin of the charger.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 140 points

    Joel,

    Thanks for the response! I am measuring the voltages of REGN and TS voltage directly at the pin. I've got the system now where the TS pin is not throwing faults:

    cat /sys/devices/platform/i2c\@9/i2c-9/am 06b/battparam
    reg 00 value 37
    reg 01 value 0f
    reg 02 value 60
    reg 03 value 00
    reg 04 value b2
    reg 05 value 8c
    reg 06 value 73
    reg 07 value 4b
    reg 08 value 84
    reg 09 value 00
    reg 10 value 20

    Do you see any other reason why the batteries would still not be charging?

    Do you see any registers I could write to that could start a charging cycle. 

    Also I want to note that QON is left floating incase that helps. 

    Thanks so much for all your help thus far!

    AJ

  • 0 in reply to Joel Hernandez II
    Prodigy 140 points

    Joel,

    Checkout these screen shots from the Oscilloscope.

    REGN:

    TS Pin

    I hope these help!

    AJ

  • 0 in reply to Andrew Keller
    TI__Guru 57651 points
    AJ,

    Please set REG01[4]=1 to enable charge and try again.

    Thanks,

    Ning.
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