What you are trying to do is OK but the circuit fails in a number of ways.

The MOSFET is effectively reversed from what it should be - the arrow on
the package shows th edirection in which current will flow through thebody
diode - at present the diode will always be conducting.
Place the MOSFET in the ground side of the load.

The current sense resistor is on the high side of the battery and the sense
amp U$1 has infinite gain - its output will be hard potitive at all times.

Place the sense resistor in the source lead of Q1. ie Q1_source - sense
resistor - Ground.
Now use U$1 to amplify this ground referenced signal by a suitable amount.
Say Imax =3D 1 amp and Rsense =3D 0.01 Ohm so Vesnese max =3D 0.1 Volt. If =
the
ADC max input is say 2.5V your amplifier gain needs to be 2.5/.1 =3D 25
The MCP6001 datasheet is here:
http://ww1.microchip.com/downloads/en/DeviceDoc/21733j.pdf

Use eg the typical application non-inverting amplifier circuit at the
bottom of page 1 to get 25x gain or whatever else you need.

A load resistor is OK. Better would be a constant current source (or sink
in this case) to provide constant discharge rate.


                 Russell McMahon
--=20
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