Hi,
We are using Bq77915 as BMS for LI-ion batteries(NCR18650B) with a 3s2p configuration.
We are measuring battery voltage using a potential divider circuit and reading it through the ADC channel of the E73-2G4M04S1B module.
We have chosen values of
R1= 604Kohm
R2= 191Kohm.
for the divider circuit. The reason for choosing high resistor values is to reduce the current through the circuit.
However, we had a problem reading the battery voltage correct due to the high input impedance of the ADC channel.
There are a few options I can think off:
1) Choosing low resistor values. But there will be mA current flowing through the circuit.
2) Having a unity gain amplifier at the out of potential divider (with the same valuesR1 as 604K ohm and R2 is 191K ohm). but the op-amp used will have offset.
3) Measuring the voltage ( with the same values R1 as 604K ohm and R2 is 191K ohm) and multiplying a correction factor to the measured voltage. But if the error during each reading is not constant, then multiplying common correction factor would result in wrong readings.
Could you please suggest which one would be good to go with? If none of the above could you please suggest a cost-effective solution for accurately measuring the battery voltage?
The battery pack is connected to the rest of the circuit through BMS.
Should the battery voltage measurement circuit be connected before the CHG & DSG Fet's or after the Fet's?
Thank-you
Warm Regards
Harini Krishna
