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Original question:

BQ25601D: Tech request for portable standalone device (RPi) with LiPo and charger and UPS behavior

BQ25601D: best IC gauge for BQ25601D and 3.6V 10000mAh single LiPo cell

FFabio
Expert 1440 points
Part Number: BQ25601D
Other Parts Discussed in Thread: BQ27Z561-R1, BQ27531-G1

Hi Team,

relating my post about the BQ25601D battery charger IC (LINK) question #3 I kindly request some advice about some solutions able to work together this IC charger or some other better alternative if there are in order to discover in a reliable way when a single LiPo 3.6V batteries bank (10000 mAh) is going to be unusable due to discharging. The goal is detect this situation safetly in order to start a proper safe shutdown for the target system.

We have to design a custom pcb that shall act as to a UPS and also have to proper inform the target system that is time to perform a shutdown because in a few time will occour a power loss and the system have to be halted in order to prevent data corruptions. As charger our first choice was about the BQ25601D because we can control it by microcontroller and then we can integrate this feature directly on our board, now the question is found the best choice in order to implement a reliable gauge monitor for this system. There are plenty of IC gauge and so we kindly require some help to perform the better choice from this point of view regarding the battery cell capacity and the charger IC.

Hope someone can give us some help about this point.

Best regards.

F.

  • 0
    TI__Guru 52115 points

    I would suggest you take a look at bq27z561-R1, which is a very popular gauge device for single-cell applications.

  • 0 in reply to Andy Liu (BMS)
    Expert 1440 points

    Thank Andy for your contribute.

    I need some clarification about how to use this IC together with the BQ25601D, I've attached an hypothesis the doubt is how to perform the ground connection between this two IC.

    The charger need to see the battery, so from this perspective this should be put on the battery ground side, but making this leave Rsense out of the load loop so no battery current measurement will done by the gauge IC, on the other hand if the BQ25601D ground will put at the PACK- side, the battery is not directly connected between the BAT pin of the BQ25601D and the related ground because between this two ground points we have the shunt resistor Rsense that may have some influence or not, I really do not know, on the BQ25601D charging algorithm, ... I'm missing somethings?

    Best regards.

    F.

  • 0 in reply to FFabio
    Expert 1440 points

    Hi Team,

    someone have suggest about this stuff?

    Thank!

    Best Regards.

    F.

  • 0 in reply to FFabio
    TI__Guru 52115 points

    Here is the basic smart battery circuit.  From a gauge's perspective, the BQ25601D ground should be put at the PACK- side.

  • 0 in reply to Andy Liu (BMS)
    Expert 1440 points

    Hi Andy,

    thank for your time.

    This solution is as into my conceptual schematic, in this one the ground of the charger (BQ25601D) is not directly connected to the battery negative pole so the charger have also the shunt resistor inside the loop with the battery, the question is if this type of connection, due to the presence of the shunt resistor, can make trouble  to the charger algorithm or not, I really do not know what can be the behavior of a such system setup. Do you have tested it in practice or just a your think as mine?

    I know that I may seem persistent, but having to make printed circuit boards I have to be reasonably certain that the system is able to work properly.

    Also in your schematic I can see the comm connection between the gauge IC and a SPDT switch to perform charge/discharge of the battery, by working with the BQ25601D I think that this is not used because the charger make itself all the needed work to charge the battery, I'm right?

    Thank for your time!

    Best regards.

    F.

  • 0 in reply to FFabio
    TI__Guru 52115 points

    No. I don't think that will make any trouble.

    Let me find a better block diagram for you.  Take a look at the BQ27531-G1 datasheet. On its first page, you will see a simplified schematic which includes a charger and also a gauge device.  Check the GND connections.

    Andy

  • 0 in reply to Andy Liu (BMS)
    Expert 1440 points

    Thank you Andy!

    Best regards.

    F.