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BQ76940: Battery Pack (48V) - Series/Parallel Connection

Mauro Basquera
Intellectual 720 points
Part Number: BQ76940
Other Parts Discussed in Thread: BQ78350, BQ76PL455A-Q1

Hello,

We are developing a Battery Pack (48V/50Ah - 15 LFP cells) with the bq76940 + bq78350 + MSP430. This product will be applied to 48V - Hybrid-Solar and Telecommunication Systems and for ESS (High-Voltage Battery - Containerized Solutions). Therefore, it will have to be able to be connected in series and parallel. 

What are the guidelines from Texas for this kind of battery in respect to isolation, charge/discharge switches (voltage rating), protection, etc..?

To illustrate, here is a simplified diagram for high voltage applications:

.

Thanks,

Mauro

  • 0
    TI__Expert 4640 points

    I would suggest you look over first into this TIDA for 20S as you will need external components to make the 940 stackable. Other than that we can recommend to look into using the bq76PL455A-I as that device can be stacked natively.

    www.ti.com/.../TIDA-01093

    Thanks

    Miguel

  • 0 in reply to Miguel Angel Rios
    Intellectual 720 points

    Hello, Miguel.

    Thanks for your response.

    Sorry if I was not clear with my drawing and explication, but the solutions you provided are All in one.

    Our battery pack (48V/50Ah) has to be able to operate stand-alone, in parallel and in series to make any voltage (1000 V - series) and capacity (500Ah - parallel). In other words, a stackable battery (series/parallel).

    For example, what we want to know is if the power switches have to be designed for 1000 V, even for a 48 V pack. This kind of guideline.

    Do you have any information or example case?

    Thanks,

  • 0 in reply to Miguel Angel Rios
    Intellectual 720 points

    Hello,

    Any updates from TI?

    Regards.

    Mauro

  • 0 in reply to Mauro Basquera
    TI__Genius 11480 points
    Hi Mauro,

    If you want a modular 48V, the pl455A is a good choice.

    I will be up front with you - designing a battery pack that is so flexible will certainly be a challenge.

    There are no blanket guidelines, but a good rule of thumb is to design for your worst case scenario. If you want your power switches to potentially switch 1kV, then they should be designed for such. It is always better to over-engineer than under engineer.

    I would also think that this document would be of relevance: www.ti.com/.../slua776.pdf
  • 0 in reply to David Wiest Jr
    Intellectual 720 points
    Hello, David.

    Thanks for you reply.

    We are not thinking about using the pl455A because of its cost and because we are already in the second version of our 48V modules using bq76940 + bq78350. The goal now is to make it modular, that's why I'm asking that.

    What could we do to implement in our module the functions/characteristics that bq76pl455A-Q1 have already included?

    We wanted to check if you have had any experience on that kind of battery pack.
    Does TI have any PCB/schematic consultancy for it?
    This BMS is part of a R&D project funded by the Brazilian government and we really expect to start production in the end of the next year.
    Until now, we've develop it only by looking at your reference guidelines (which are really good) and E2E.
    However, we think it would be great a direct contact with someone from TI to help us with that.
    I will send my email to your inbox.

    Regards,

    Mauro
  • 0 in reply to David Wiest Jr
    Intellectual 720 points
    Hello, David and Miguel.

    Any info?

    Regards,
  • 0 in reply to Mauro Basquera
    TI__Genius 11480 points
    Hi Mauro,

    I sent you a message - we can discuss further.