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BQ40Z50-R2: What are registers or value will affect SOH?

Che yi Su
Expert 1695 points
Part Number: BQ40Z50-R2
Hi TI experts,
I follow battery spec to setting Design capacity and Qmax by typical value. After learning cycle and update status=0e for new battery, BQ40Z50-R2 report SOH not 100% and TRM show the formula is FCC/Design Capacity and relation with SOH load rate. But it's not true, I found below value and setting will affect. 
1. Current at EOC.
2. Higher term voltage cause DOD error or over discharge below term voltage.
3. SOH load rate => less influence.
4. Design Capacity(mAh)
5. Wrong ChemID.(Best chemical ID max. deviation, % : 0.66)
6. SOH FC@25C Q
Q1. Anything else?
Q2. How to setting Design Capacity(mAh)? By battery typical or minimum value? 
Q3. Is SOH not be 100% is normal?
Q4. SOH formula looks like SOH FC@25C Q/Design Capacity. What are registers or value will affect SOH FC@25C Q? If I modify Design Capacity to let SOH be 100%, what's condition need to pay attenetion?
Need TI menmber help me to check it, many thanks.
  • 0
    TI__Mastermind 42535 points

    Hi Che yi,

    SOH load rate is the load rate used for calculating SOH. SOH is FCC at 25C/ design capacity. FCC at 25C is calculated with load rate set to SOH load rate. Set design capacity as battery capacity in DS if you are charging to termination per cell DS. SOH not reporting 100% even in new cells is not unheard of. You can increase SOH load rate to increase SOH reported.