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BQ35100: BQ35100

Luis Miguel Martí
Prodigy 10 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO

Hi Team,

I'd like to know how cells in parallel affect the EOS feature of the BQ35100. I'm willing to use 2 Li SoCL2 (chem ID 0659) in parallel but after checking in BQStudio I cannot find a place to tell this to the BQ35100 nor change the resistance to half which, I guess, would be the expected with two cells in parallel to detect the EOS.

Could you let me know if there's a need for any specific configuration using batteries in parallel?

Also, I'm quite lost in the usage of this device. When using the EOS mode, does the MCU have to wake up the gauge and start it anytime or it just have to wait for the alert pin to be asserted?

Best regards!

Luis Miguel

  • 0
    TI__Guru** 104905 points

    Hello Luis,

    The gauge will adjust the resistance during the first couple measurements automatically to align with the Ra table we have stored from the chem ID. I would not recommend using any SOH data from the gauge in EOS mode with LTC battery chemistry. As noted in the TRM the error can be very high and the EOS alert function should be used instead to identify when the battery is near end of life.

    Have you been able to review our application notes on using the device in EOS mode?

    https://www.ti.com/lit/pdf/sluaal7

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 10 points

    Hello Wyatt,

    I checked the application notes and followed the setup steps with BQStudio. However, I find the application note more helpful for the characterization of the cells than for the use of the gauge itself. After using the new battery command and setting gmsel it does not say whether you need to use the seal command. Anyway since I'm using an already existing chemistry I think I don't need to go through this test process, right? So after setup, the BQ35100 should be ready to work, is that so?

    About the alignment, do I need to do them with the BQStudio? After these first couple of measurements, does the MCU in my circuit have to enable ever again the gauge if I'm not willing to get SOH?

    Best regards!

  • 0 in reply to Luis Miguel Martí
    TI__Guru** 104905 points

    Hello Luis,

    Seal command is only used if you want to protect your settings if someone gets the pack and it is not sealed everything can be exported, it is optional depending on the application security level required.

    The chem ID is not related to the EOS alert feature, you must verify at what point the alert should be set based on your testing while logging the resistance reported by the gauge. When the EOS alert feature is used the chem ID is not used at all, the chem ID is only used if you want to attempt to get SOH percentage data and the gauge will correlate the Ra table from the chem ID to the SOH %.

    No the gauge must wakeup before a load pulse and be enabled to measure the resistance. You cannot leave the gauge in shutdown, it needs to learn the resistance over the lifetime of the pack.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 10 points

    Hello Wyatt,

    That explains a lot about the process. Thank you so much.

    Do I have to measure the scaled R of one of my batteries to set the threshold for the EOS alert? Like measuring the scaled R for the whole battery life and discharging it completely. My batteries are LiSOCl2 like the ones in the example of the document but not the same model.

    Best regards!

    Luis Miguel

  • +1 in reply to Luis Miguel Martí
    TI__Guru** 104905 points

    Hello Luis,

    That would be my suggestion, is using a accelerated method to age the battery like what was used in the application note.

    Or if you have the data from the manufacturer you can use that as well, it depends how much data you have on the cell and how accurate you need the alert to be (what SOH % you need to trigger the alert).

    Sincerely,

    Wyatt Keller 

  • 0 in reply to Wyatt Keller
    Prodigy 10 points

    Thank you so much for your help Wyatt!

    Best!

  • 0 in reply to Wyatt Keller
    Prodigy 20 points

    Hello Wyatt,
    thank you very much for the quick reply.
    We are using two SL2870 in parallel with an additional Tadiran HLC "Super Capacitor", can we use the EOS notes you liked above for that as well?
    And we are using other Tadiran primary cells on their own, for which there is no chem ID either. Can we use the mentioned method "stand alone" or do we need the chem ID Information as well?
    I would be glad for any hints. If it is better to make a new post for that, I can do that as well.
    Thank you very much in advance,
    all the best
    Dirk

  • 0 in reply to Dirk
    TI__Guru** 104905 points

    Hello Dirk,

    It may be better to make a sperate post to allow better tracking since this one has been idle for a long time.

    For super capacitors in parallel this will make it more difficult for the gauge to correlate the voltage/current to internal resistance, which would make it very important to do an accelerated test to make sure the EOS alert will work as expected in the system. You do not need the chem ID in order to use the EOS alert feature.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 20 points

    Hi Wyatt,
    thank you very much, I will do so. Just a quick idea, would it benefit the accuracy if the super capacitor would be placed after the gauge shunt instead of directly parallel to the batteries?

    Sincerely,
    Dirk

  • 0 in reply to Dirk
    TI__Guru** 104905 points

    Hello Dirk,

    I don't believe that would have much impact since it would still be adding the time constant to the measurements of the battery so it wouldn't be the true battery voltage under load.

    Sincerely,

    Wyatt Keller