I want to measure lead-acid battery voltage on ESP8266. Approximately range is 12-14V.
In fact, I think even 0.1V resolution is enough for me, so this is more a theoretical question.
ADC is 10-bit 0-1V, probably as usual it is more marketing number, but i guess i can get real 10bits by a little bit of oversampling.
Even if i use 5% tolerance resistors 14k/1k(i can always calibrate divider), corner case max voltage (13300/1050) is 1.024V, still OK.
Precision drop in worst case (max 0.85V) (9.7bit), this means ~0.016V precision.
What if i add some inexpensive R2R opamp (MCP6041?) in inverting scheme and shift with virtual ground 12V, range to 12-14V, with gain 0.5?
Such way my measurement will stay within 2V, which might be ~0.002V precision, but i add in equation imperfections from opamp itself.
Is it worth to do such way if i want to improve the resolution of the measurement?