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BQ2084-V143: BQ2084 Midrange Capacity Corrections

Christian Hoppe
Prodigy 40 points
Part Number: BQ2084-V143
Other Parts Discussed in Thread: TEST2

Hi,

we use the BQ2084 for our batteries. In our current application we are having some trouble with low currents. The capacity from the gauge differs from the real capacity of the battery after some time.

So we are thinking of activating the midrange capacity correction. In the datasheet is the following table:

My first question is if the second row from the table should be "<VOC75 and RelativeStateOFCharge()    >   87%"? Otherwise it makes no sense in my opinion?

In our applciation we have low currents (<1mA) for longer periods of time and some short periods with currents like 300mA. After some time there are major deviations from the real capacity. Because of this deviation, it is not possible to fully charge the battery because of the Maximum Overcharge value which is 300mAh in our battery.

 

Do you think the midrange correction will help us or is there another solution you would recommend?

 

Regards,

 

Christian

  • 0
    TI__Mastermind 25955 points
    Hi Christian,

    Thank you for the post. This thread will be updated with a response before the COB on Tuesday.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    TI__Mastermind 25955 points
    Hi Christian,

    Could you please send a log and a gg file of your gauge settings? Thank you!

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Prodigy 40 points

    Hello Bryan,

    I dont have a log file for discharging with low currents because the test took 3 month in our apllication. In this test a lowpower Controller runs the whole time with about 0.5mA. Every 30 minutes it starts the system which needs about 300mA for 20seconds. After this 3 month i read the battery. The BQ2084 said the battery is still on ~80%. But the battery voltage and the calcualting of the powerconsumption showed me that the battery had about 25% remaining capacity.

    (I know the deadband current is 3mA in my configuration, but setting it to 0mA gives me an offset of about 1mA, so the problem of the capacity deviation is the same.)

    I started charging the battery from the 3 months and it couldn't be fully charged because the BQ set the Overchargebit for the maximum Overcharge Capacity of 300mAh. I had to discharge the battery a little bit and started the charging again for the next 300mAh. You can see the charging procedure in my log file.(92d_Test_charging_from 81%.LOG and 92d_Test_charging_from 100%.LOG )

    To solve the problem tried to activate the midrange capacity correction last week and it didnt work for me.

    For testing i activated the Midrange capacity correction with test values. I set the Gauge configuration to 0x43h. As VOC75 i chose 16500mV to reach the voltage after a short time and to have the capacity deviation described in the data sheet. I expected that the BQ2084 will change the RM to 75% when the battery reaches 16500mV, but nothing happened.VOC 50 was 16400mV and it didnt changed the RM  neither.

    I discharged the battery with 45mA. Logfile:VCOR_set_dicharging 45mA_VOC75_16500_Test2.LOG

    I don't know why the midrange correction doesnt work for this configuration. (see Gauge_Configuration.txt). I hope you can find my mistake and we can solve the problem. Maybe i overlook something.

    BQ2084_Midrange_correction.zip

    Regards,

    Christian

  • 0 in reply to Christian Hoppe
    TI__Mastermind 23391 points
    hi dears,

    any help is more than welcome here...

    thansk a lot in advance
    KR
    Vincenzo
  • 0 in reply to Christian Hoppe
    Prodigy 40 points
    Hello,

    i want to get the midrange capacity correction running. Some hints why it's not working with my configuration would help me a lot.

    Thank you!