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BQ40Z50-R2: Requirement of chip for stackable multicell application

Rohit Panchal
Prodigy 45 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ34Z100, BQ769142, BQ77216

Tool/software:

Hi everyone,

I'm looking for advice on selecting correct chipset for my bms that can switch between 4S2P and 8S1P configurations, as per the requirement.

My idea is to use two 4S1P battery packs, each with its own chip. Then, I would use a microcontroller to change the connection between them either in parallel (to make 4S2P) or in series (to make 8S1P).

I have a few questions: can this be done with a stackable chip? Is this the right approach? and is it doable? Which chip would be suitable for this kind of setup? 

Any suggestions on the design, chip selection, and with switching method would be really helpful.

Thanks & Regards,

Rohit

  • 0
    TI__Mastermind 31800 points

    Hello Rohit,

    This is possible and can be done the only issue for this project is that since you are wanting to do 8 cells in series than you would have to go with BQ34z100. One you decide what cells you want to use you would do the process start from finish with on the 4s2p pack and than export the golden image. You would then do the same thing with the second 8S1P pack and than export the golden image with it too. Than for the finial product the Host would need to be able to identified which pack the user is using and than reflash the battery gauge with the golden image to properly use it. I've attached a document for communication with the gauge and the host

    Gauge communication:
    https://www.ti.com/lit/an/slua801/slua801.pdf?ts=1746546787938&ref_url=https%253A%252F%252Fwww.google.com%252F

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 45 points

    Hi Alan,

    Thank you so much for the quick and helpful response.

    In the meantime, I have also been doing some research and wanted to share a few more information.

    My cell configuration is fixed as 8S natively (8S1P), and that will be the default mode. When needed, I will switch the configuration to 4S (4S2P) using an MCU. The switching frequency between 8S and 4S will be relatively high in my application.

    So, I wanted to ask would it be possible to achieve this using a battery monitor/balancer IC instead of a gauge like the BQ34z100? using stacking option? Can you please put some light on this approach as well?

    Addtionally can i avoid rewriting the full golden image every time the configuration changes, it would really help, because i want to preserve lifetime data and relative full charge capacity, etc data, especially as the battery ages. I’m okay with updating essential parameters when series configuration is being changed

    I want to simplify this as much as possible.

    Thanks again!

  • 0 in reply to Rohit Panchal
    TI__Mastermind 31800 points

    Hello Rohit,

    Rohit Panchal said:

    My cell configuration is fixed as 8S natively (8S1P), and that will be the default mode. When needed, I will switch the configuration to 4S (4S2P) using an MCU. The switching frequency between 8S and 4S will be relatively high in my application.

    -I can't speak for battery monitors since I am not part of there team but I would encourage you to reaching to seeing if this is possible with there devices

    Rohit Panchal said:
    Addtionally can i avoid rewriting the full golden image every time the configuration changes, it would really help, because i want to preserve lifetime data and relative full charge capacity, etc data, especially as the battery ages. I’m okay with updating essential parameters when series configuration is being changed

    -If you want to update your parameter's, chemID and calibaration than you would need to "flash" the system with a new golden image each time. 

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 45 points

    Hi Alan,

    Alan Frias said:
    I can't speak for battery monitors since I am not part of there team but I would encourage you to reaching to seeing if this is possible with there devices

    - Can you please put me touch with them or if possible, can they reply on this thread here?

    Alan Frias said:
    If you want to update your parameter's, chemID and calibaration than you would need to "flash" the system with a new golden image each time. 

    - Thanks, understood. I believe changing chemID is not required since battery pack construction is not going to be changed when switching the series.

    Furthermore while researching on forum for something similar project, fortunately i found the exact thread which matches my requirement. Here is the link to that thread. Thread is from 6 years ago, so if anyone can from battery monitors team can guide me how it can done with latest part, it would be really helpful.

    Thanks & Regards,

    Rohit 

  • 0 in reply to Rohit Panchal
    TI__Mastermind 31800 points

    Hello Rohit,

    I am pushing this away from the battery gauge team to battery monitors team.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 45 points

    Thanks Alan! I am still awaiting for an reply from battery monitors team.

  • 0 in reply to Rohit Panchal
    TI__Expert 5645 points

    Hi Rohit, 

    Apologies for the delay on getting back to you.

    What are the requirements of your BMS? Do you need just protection, monitoring or gauging? We do have solutions for all types and you can filter on ti.com based on your systems specs and narrowed down the search to a few devices. 

    For monitors and protectors: https://www.ti.com/battery-management/monitors-balancers/products.html

    Regarding, stacking vs no stack, as your solution is <8s, you can either use a single IC that can provide monitoring/protection to all 8 cells, and can be configured to a smaller number of cells (most of our devices are able to do that). Then on your circuit you can have switches control by your host to changed the configuration to smaller number of cells. Another alternative is use a 4-s monitor/protector which the available to get stacked and again changed the configuration based on your needs. You can in theory stack any devices with external circuit, but we do have native stackable devices, but those are more fit for high voltage application (>16s). 

    There isn't a better answer is all depend on your applications requirements, I would recommend to look into our parts and post a new question on the forum if you need specific help on how to achieve your needs on either of them. 

    For general recommendations, If you are just looking for a <8s protector only, I will start with BQ77216, and if you need a monitor you can look at the BQ769142. 

    Regards, 

    Arelis G. Guerrero