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BQ40Z80: bq40z80 for drones flight batteries

Jarno Puff1
Prodigy 20 points
Part Number: BQ40Z80

We are planning to start developing a new retrofit BMS kit for drone flight batteries based on LiPos. The kit should be modular, that means a base board with the bq40z80 ic, a LED with push button board, a shunt board and a FET board. This to accomplish various application requirements ranging from simple cell monitoring without columb counting and protections to full features including protections.

flight batteries usually don’t want to have discharge FET protections as this will terminate the flight and to crash the drone. However, the pre-discharge FET will be a good feature to avoid sparks in the connectors as the load are motors with ESC with high capacitors.

will it be possible to use the pre-discharge FET only?

will be a modular design based on more boards be a viable solution?

we also handle high current up to 150 Amps. Is there any reference design to use a current hall sensor connected to the shunt pins using a resitor voltage divider?

I have more questions, but would like to go through it step by step.

Thanks,

Jarno

  • 0
    TI__Guru** 105760 points

    Hello Jarno,

    EDIT: there is a pre-charge and pre-discharge FET.

    It should be fine to make it modular, as long as the unused pins are terminated correctly.

    I have not seen a shunt be replaced with a hall sensor, usually the resistor/registers are scaled to accommodate higher capacities/loads.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 20 points

    Hi Wyatt, sorry for the long delay. Happy New Year!

    The EVM shows a Pre-Discharge on page 15: 

    The replace of a shunt is to avoid heat on the shunt and to accommodate ring style hall current sensors to easily upgrade dumb battery packs with a BMS.

    Thanks,

    -Jarno

  • 0 in reply to Jarno Puff1
    TI__Guru** 105760 points

    Hello Jarno,

    Happy new year!

    Are you wanting to implement only with pre-discharge? You will need to check the TRM if the conditions for the pre-discharge FET are what you need in your system.

    Since I haven't seen this implementation before I would not recommend using a hall sensor to then feed a voltage to the SRN and SRP pins, this could lead to high error in the current measurements.

    Sincerely,

    Wyatt Keller