This is my first trying on arduino and it is my engineering design project. This is pretty simple to make.
First of all, you need to know how you can measure analog and digital value on Arduino. Atfter you read these values, you can achive SOC (state of charge) and mAH (mili Amper Hour) by writting some codes. (I used 1.5 Volt Battery, so I design a code according to it.)
There are some constant values on the code.
Maximum voltage value is 1.5 V
Minimum voltage value is 0.9 V
Maximum mAH value is 1500 (mAH)
In other words;
When your battery level is 1.5 Volt, your SOC value is %100 and your capacity is 1500 mAH.
When your battery level is 0.9 Volt, your SOC value is %0 and your capacity is 0 mAH.
This is my SOC formula, SOC=(voltage-0.9)*(100/0.6); (voltage= Analog value of battery)
And this is my mAH formula, mAH= ((voltage-0.9)/0.6)*1500;
1) Arduino Uno
2) LCD display (16x2)
4) 10K resistor
5) 2.2 resistor (1 Watt) (This is important for your Arduino not to burn!)
This is easy project. But it helped me to improve my Arduino knowledge. I hope, it helps you, too.