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Original question:

BQ77915: BMS for 2-4 Prismatic Cell

BQ77915: Guidance on BMS circuit

Rahul Raj0
Prodigy 30 points
Part Number: BQ77915
Other Parts Discussed in Thread: BQ77905, , BQ76920, BQ40Z50-R2, BQ4050

In continuation to the discussion in https://e2e.ti.com/support/power-management/f/196/t/779439?BQ77915-BMS-for-2-4-Prismatic-Cell, we have also come across a solution (which I am attaching here)

BMS Specification-HLT-715C.pdf

Can you please guide us to understand what kind of purpose this circuit is achieving. Will it be able to
1. Measure Voltage of Cell
2. Measure Current
3. Measure Temperature
4. Calculate SOC and SOH
5. Protect for Over Voltage, Under Voltage, Over Charge Current, Over Discharge

Thanks a lot for your help.

Regards,

Rahul

What is this achieving. 

  • 0
    TI__Guru 54715 points

    Hi Rahul,
    The board you indicate is a protection circuit for apparently 3 or 4 LiFePO4. It may provide similar function to the bq77905 but with the specific levels shown in its specification. It has the separate balance ICs shown. Together they would function similar to the bq77915 in the post, but again at levels specified intended for LiFePO4 cells.
    You should check with the board or component supplier for capability, but the drawing indicates it is a protector without a communication interface, so it is unlikely to provide cell voltage, current, temperature, SOC or SOH. It should protect against the conditions beyond its limit.

    To measure parameters you would need a monitor device such as bq76920, together with an MCU you could make a system to recover the voltage, current, temperature, allow balancing, and calculate SOC/SOH according to your desired algorithm.  A gauge device such as bq4050 or bq40z50-R2 would implement those behaviors as determined by its programming and the parameters you select.