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BQ27421-G1: Initial reading of SoC 3-4% after loading Golden Image and Soft Reset FG but actual SoC should be 20+%

Part Number: BQ27421-G1


Tool/software:

The problem I'm experiencing that the SoC reported by the the BQ27421-G1A EVM report around 2-3% SoC when there is in fact 20+% SoC for a battery. The steps to arrive at this situation is:

  1. Cold boot the evaluation board  with battery at the noted state (3.546V or and about 20% SoC).
  2. Load Golden Image configuration from file to Battery Studio.
  3. Programming the golden sample image information (Ra Table, QMAX) results using Battery Studio and EVM2400 -  Write All button.
  4. Soft reset the FG using Battery Studio and EVM2400.
  5. Scan FG and SoC shows 3% and open circuit voltage is 3.564V.

The following is my configuration

QMax Cell 0 = 16597
Reserve Cap-mAh = 0
Load Selection/Mode = 0x81
Q Invalid MaxV = 3803 mV
Q Invalid MinV = 3752 mV
Design Capacity = 200 mAh
Design Energy = 740 mWh
Termination Voltage = 2950 mV
T Rise = 20
T Time Constant = 1000 s
SOCI Delta = 1
Taper Rate = 100 
Taper Voltage = 4100 mV
Sleep Current = 10 mA
V at Chg Term = 4194 mV

Ra Tables:

R_a0 0 =65
R_a0 1 =65
R_a0 2 =55
R_a0 3 =58
R_a0 4 =43
R_a0 5 =57
R_a0 6 =94
R_a0 7 =94
R_a0 8 =81
R_a0 9 =74
R_a0 10 =89
R_a0 11 =107
R_a0 12 =216
R_a0 13 =569
R_a0 14 =904

The battery datasheet is attached

  • Hello Chris,

    SOC is not going to be accurate on the initial boot after programming the golden image. You will need to cycle (charge and discharge) the battery once and then SOC will be accurate.

    Regards,

    Adrian