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Very High Capacity Lithium Ion Battery Management System Info

Darren DeBattista1
Intellectual 525 points

Hi All,

We are designing a new battery pack which would be used in a future product. This battery pack would be large, totaling at about 2000Whr. We were of the thought of making an 8S30P battery pack but issues started to come up when it came to battery management. Apart from the large currents involved, we were in doubt on how to structure the BMS for ex, should we use a single 8S BMS chip and make 8 packs of 30 cells in parallel (which I think could be dangerous having so much cells in parallel), or should we make packs of (say) 8S3P with a BMS for each pack and than use 10 packs in parallel. The later option could induce issues since we have no control on how much current each pack would be contributing. 

In the end, is there anyone with experience on such battery packs which could supply some guidance and also links to white papers and applications notes?

Thanks

  • 0
    TI__Guru 54715 points

    Hi Darren,

    Both approaches have challenges as you indicate.  For the large parallel groups the BMS can monitor the voltage of the cells and temperatures as you decide to monitor them, but it can't tell how current is flowing inside the parallel group.  For multiple strings you have issues of how to switch the sub-packs together and how the system behaves if one sub-pack decides it has a fault.  For example if you have a heavy load on the system and one sub pack decides it is hot and turns off the remaining subpacks must provide the system current and may overheat in quick succession. Other faults may happen similarly.  When bringing the sub-packs together consider what will happen if the packs are at different voltages and how they are equalized before connecting together. Your system design will need to determine how to react to these situations.  

    I'm not aware of specific application notes or papers on this topic, you may search for online resources, or other forum readers may comment.

  • 0 in reply to WM5295
    Intellectual 525 points

    Dear WM529,

    Thanks for your reply. I'll search for more information.