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BQ40Z50-DEVICE-FW: Battery Packs Parallel Connection

POWER TEAM
Prodigy 90 points
Part Number: BQ40Z50-DEVICE-FW
Other Parts Discussed in Thread: BQ40Z50

Hello,

I made several 4S7P Li-ion battery packs with a capacity of 21Ah each, using the BQ40Z50 as BMS.

Now I'm required to provide a 42Ah pack and I wonder if it is possible and safe to connect two of the previous packs in parallel, which means to short the outputs and the communication buses of the packs, while each one has it's own BQ40Z50 as BMS.
If so, what am I required to do besides making sure that the packs' voltages are identical before I connect between them?

Besides this proposal being more versatile, I'm aware of the 32,767mAh capacity limit of the BQ40Z50.

Best Regards!

Itay

  • 0
    TI__Guru** 102415 points

    Hello Italy,

    If you are designing a new BMS you can scale the current value in the gauge so you can do higher capacities. For example if you apply 2A and calibrate the gauge saying it is 1A, then all of your mA/mAh unit parameters can be scaled by 1/2 and you can reach up to 64Ah.

    For doing parallel connection, as long as the gauge is not in broadcast mode or there is something that could cause issues with the pull-up references it should be fine if they have a separate BMS. The gauges don't have arbitration so if you tie the communication lines together you will not be able to communicate with them unless they have different addresses programmed.

    Sincerely,

    Wyatt Keller