4S LiFePO4 Battery Voltage Monitor with Open-Wire Detection and Removable Cells

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Hi,

I’m seeking advice for a project involving a 4S LiFePO4 battery pack. My key requirements are:

  1. Accurate Cell Voltage Monitoring: I need to measure individual cell voltages in a series-connected pack.
  2. Open-Wire Detection: The system should reliably detect when a cell is physically disconnected (i.e., reading 0V or open-circuit conditions).
  3. Handling Removed Cells: The IC should continue monitoring the remaining cells accurately, even if one or more cells are removed from the stack.
  4. External MCU Integration: I’ll interface the monitoring system with an external microcontroller via I2C or SPI.

I initially considered using precision rail-to-rail op-amps (like the OPA4197) configured as differential amplifiers to measure cell voltages as is done here:

However, handling floating inputs when cells are removed has proven to be a non-trivial design challenge. To simplify the design, I’m considering dedicated battery monitoring ICs for voltage readings and open-wire detection, with the TI BQ76952 or BQ76942 as a potential candidate.

I'm unsure if I will continue with my op-amp setup or shift to a dedicated battery monitoring IC. Does anyone have any suggestions for handling floating inputs to a differential op amp when a cell is removed?

Thanks.

Link to TI product: https://www.ti.com/product/BQ76942

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