It seems OP wants to measure voltage and current of a 12volt SLA battery.
Voltage can be done with 1.1volt Aref,
but the ACS current sensor that OP has must be used with default Aref.
Better to ditch all those sensors, and switch to an I2C sensor made for the job,
like an INA 226 (16-bit) or INA219 (12-bit) breakout board.
Leo..