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BQ79656-Q1: BQ79656 Daisy chain communication system on multiple series and parallel connection

sangjun lee
Prodigy 10 points
Part Number: BQ79656-Q1

Tool/software:

Dear

I am trying to build a battery system with TI solution(BQ79600/BQ79656).

The concept of this system is connecting multiple 48V sub modules in parallel and series.

In each sub module, single BQ79656 will be used and in the master side, single BQ79600 will be used as a gateway of this daisy chain communication

Communication will be made mainly with daisy chain and making a loop based on BQ79600.

System will look like the image below;

In this system, daisy chain must go through different voltage range with repeated increasing/decreasing direction. (96V=>48V=>48V=>96V=>...)

I am wondering if this type of daisy chain communication system would work properly or not. 

The reason of this system concept is I am actually planning to build a system with some flexibility for the number of packs in the system from 2S1P to 2S4P in sub module level. 

I would like to have an official feedback from TI engineers regarding this concept. 

Thanks in advance and have a great day

Regards

  • +1
    TI__Expert 4610 points

    Hello,

    I believe that this could technically work. What you will have to be mindful of is making sure that the device grounds are done properly. You need to ensure that the devices with 48-96V are grounded to the highest potential of the 0-48V devices. Otherwise, you will have accuracy issues.

    Thanks,

    Zachary

  • 0 in reply to Zachary Balov
    Prodigy 10 points

    Hi! Zachary

    Thanks for your answer!

    That is truly helpful.

    I have some more questions regarding this system concept. 

    1. Will this type of connection work as well?

    Daisy chain will go through all 96V range modules and then go down to 48V modules.

    2. Is there any restriction of daisy chain connection?

    if the system concept that I asked in the main query would work properly and if the concept of question no.1 works well too, 

    it seems like there is no physical/electrical limitation of daisy chain connection.

    I am wondering which type of connection I must consider as 'not-working'

    Thanks in advance

  • +1 in reply to sangjun lee
    TI__Expert 4610 points

    Hello,

    All VIF is, is an isolated communication architecture, independent from the HV side of our BQ devices. As long as the general concept of N-->S and S--> N connection is followed, you will not run into issues. It's then your responsibility to make sure the HV design is correct.

    Thanks,

    Zachary