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BQ27421EVM-G1B: Requesting Suggestion for interfacing BQ27421-G1B-EVM and BQ25611D-EVM

Anonymous
Intellectual 275 points
Part Number: BQ27421EVM-G1B

Tool/software:

Hi TI,
   I’m using the BQ27421-G1B-EVM board for gauging purposes and BQ25611D-EVM for charging the battery. According to the data sheet, I confirmed that the BQ27421-G1B-EVM is programmed with CHEMI_ID of 312 for a Li-ion battery. I’m assuming that this would be suitable for a single cell LiPo (LiCoO2) battery with a full charge voltage of 4.2V (My assumption is that BQ27421-G1B is programmed for 4.3/4.35V).

Below are the battery details for your reference.

Rated Capacity

typical 5200mAh, min 5100mAh

Nominal Voltage

3.7V

Charging Voltage

4.2±0.03V

Standard charge

Constant Current 0.2C5 A, Constant Voltage 4.2V

0.01 C5 A cut-off

Standard discharge

Constant current 0.2 C5 A

end voltage 3.0V

Fast charge

Constant Current 0.5C5 A

Constant Voltage 4.2V

0.01 C5 A cut-off

Fast discharge

Constant current 0.5 C5 A

end voltage 3.0V

Maximum Continuous Charge Current

1 C5 A

Maximum Continuous Discharge Current

1.5C5 A
( Pulse discharge current: 2C )

Anode

Carbon fiber

Cathode

Lithium Cobalt Oxide;LiCoO2

Electrolyte

EC/DMC/EMC/LiPF6

Separator

Polyethylene/ 20 mic
  1. I had given my battery specs below. Can you confirm whether the selected Charger and gauging is compatible for this battery?
  2. What is the right method to validate the Gauging Vs actuals
  • 0
    TI__Guru 62386 points

    I don't know about the charger. The bq27421-G1A would be a potentially better fit for a 4.2V cell than the bq27421-G1B. You'd have to use https://www.ti.com/tool/GPCCHEM for an analysis if the actual cell chemistry is compatible (this tool returns an estimated DOD error for the cell under test and all bq27421 variants).

    Validation is up to the customer. A simple way to validate gauging accuracy is to log time, current, voltage and SOC from a full charge to a full discharge and then calculate the true state of charge for this data by dividing coulomb count (=integrate the current over time) for each time by the total passed charge (=full charge capacity) and multiplying this by 100%. The difference in each line in the log file between true SOC and gauge reported SOC is the error in percentage points.