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BQ76920EVM: Give suggestion on Battery Monitoring System

Amit Parmar
Prodigy 20 points
Part Number: BQ76920EVM
Other Parts Discussed in Thread: ISO1541, BQ76930EVM, EV2400, BQ76930, BQ76940, BQ34110, BQ34Z100-G1

Hello,

I want to "monitor" the discharging and charging scenario of 2 LifePO4 12.8 V 64Ah battery connected in series(Providing 24V supply). Please suggest me which EVM I can use for this?

 

  • 0
    TI__Guru 54715 points
    Hi Amit,
    A 12.8V LiFePO4 would be a 4 cell stack. You will need to get to the individual cell voltages to monitor the cell voltages.
    If the batteries have protection switching internal they can be monitored with bq76920EVMs. An isolator such as ISO1541 will be needed to communicate to the top device due to the voltage offset. A bus mux or separate busses will be needed.
    If the batteries are cell stacks without protection you could monitor them with a bq76930EVM.
  • 0 in reply to WM5295
    Prodigy 20 points

    Hello,

    Thank you for the reply. Battery doesn't have protection and I don't have access to each cell. I want to monitor discharge current and voltage at lease. And battery is of 64Ah with 12.8V and it's customised LifePO4. Will bq76930EVM will be able to go for all these conditions mentioned above.

    In addition to that, As I have gone through some other requirements of this EVM, we need EV2400 Interface module with bq76930EVM. One more query from my side- Do we need to have to have EV2400 or can we get data through I2C directly from bq76930EVM?

    And is this setup of bq76930EVM and EV2400 good to mount on moving platform? 

  • 0 in reply to Amit Parmar
    TI__Guru 54715 points
    Hi Amit,
    If you have the bq76930EVM, you can talk to the bq76930 with any I2C device. The bq76940 evaluation software will only talk through the EV2400 or EV2300. If you want to talk to the part from a PC, use your available I2C adapter and your own program. If you are using a MCU connect its I2C to the bq76930, check signal levels and use a level translator if needed.
    However, if you can't get to the individual cells the bq76930 will not be useful.
    The bq34110 and bq34z100-G1 are pack level gauges which can measure voltage and current, but they use an average cell voltage, and the EVM may not support such a large battery if current is high. You might look at circuits for your MCU, perhaps an INA to sense current and level shifting to get battery voltage to your MCU's ADC.