Hall effect current sensor ACS712 for battery application
ACS712 has 3 different types. These are 5A, 20A and 30Ampere versions. The sensitivities are 185 mv/A , 100mv/A and 66mV/A . Actually if these values are good for your system, just hook up the VIOut pin directly to MCU ADC input pin. Be sure VDD of ACS712 is same as VADC voltage  of MCU.
If you need more you can use amplifier circuit for increase the sensitivity up to 610mV/A.