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BQ77915: BMS for 2-4 Prismatic Cell

Rahul Raj0
Prodigy 30 points
Part Number: BQ77915
Other Parts Discussed in Thread: BQ77905, BQ77904, BQ2962

We are working on Low Voltage Lithium ion batteries, for example 12.8V/80AH batteries or 12.8V/40AH batteries. These batteries are LFP batteries, made from cylindrical or prismatic 3.2V LFP cells. Cylindrical cells have low AH (5-6AH) values hence 16 cells are needed for making 12.8V 80AH battery. Prismatic cells have high AH (20AH) values hence 4 cells can give 12.8V 80AH combination. 

We want to build a BMS which can have better control. The BMS should 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 Disc
  6. Collect and display required data

According to our application, we shortlisted the following ICs:

  1. BQ77915
  2. BQ77905
  3. BQ77904
  4. BQ2962

However, I think experts can suggest better ICs for the same. Please guide us

  • 0
    TI__Genius 10830 points

    Hi Rahul,

    Based on your requirements (SOC, SOH), you're looking for a gauge, not for a protection IC.

    Please look at the parametric search engine for our battery fuel gauges (link here). I took the liberty of doing some filtering based on your requirements and came up with 2 devices that are suitable. I'd recommend you look at the bq40z50-R2 (with the latest bq40z50-R3 FW, downloadable separately).

  • 0 in reply to David Hien
    Prodigy 30 points

    Hi David,

    Thanks a lot for the reply. We will check the details. 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