I have a question regarding the usage of op amp to measure battery voltage. I know there are battery gauge IC's dedicated for that, but I'm trying to do this to both understand the op amps better and the other one is that this solution should be cheaper since I don't need a super precise measurement.
So, I had this circuit and math in mind:
VIN - Battery (Li-Po 2S 6-8.4V range)
I'm using a voltage divider with R1 and R2 to get 1/10th of the input voltage and feeding that into op amp that is configured for gain of 3. So my calculation is:
VMEAS_BATT = (VIN / 10) * 3
which would give me an VMEAS_BATT range of 1,8V to 2,52V (when battery is full).
I would feed that voltage then into MCUs ADC input and read and do the math to get the battery voltage reading.
Can you please help me by checking if this is a "sane" circuit, is math correct and at the end what would be other practical considerations that I would need to consider to make this circuit work?