@ johnerrington: Thank You ! It was a very useful link (I add 1 Karma :-).

As I saw in

this link there are 3 points for consideration:

1) Coulomb Counter (Battery Fuel Gauge)

Measure the current instead of ACS712 with INA216 (datasheet attached), because it is more accurate

Okay, I attached my schematic.

But in the same thread I dont' understand this:

An INA216 breakout board could be a better solution for your (unspecified) project.

Voltage, current, power, all in one.

Leo..

The terminal voltage not measured with INA, just volt drop on shunt. So the LM4040 AIZ-4.1 diode and voltage divider shall remain.

2) Calculate the capacity consumption as I(load)*time and store. Later subtract from nominal capacity of the battery (2200 mAh).

3) How the whatever state of the battery can be taken ? For this we have to know the actual voltage and discharge curves. (Already solved in this thread :-)

Anyhow, we need voltage value, because if the terminal voltage reach the cut-off value, we have to be re-charged.

So I would like combine the till achieved results with the new one (point 2&3):

I know the voltage & temperature, so when I start the rover, I can take a low 0.1C discharge cure as reference. -> I know the initial battery state and how much max. capacity is possible on the actual temperature (for example @ -10C (green line) only 75% of the max. Let saying 12Ah battery 12*75%= 9Ah max).

If I start the rover and measure the terminal voltage let say showing: 12 V, then it means 25% already consumed (12 Ah* 25% = 3Ah). (See on the discharge curve.)

So If I run the rover over a certain time, I can collect / calculate / integrate the I(load)*time.

Recharge required when this equation is less than zero: 9Ah - 3Ah - I(load)*time.

With this, the dependency of the discharge cure from the c-rate is resolved, but during operation the temperature shouldn't changed. C = (fv, ft)