Acs712 sensor issues

Hi, I am using an acs712 30A sensor to measure current from a 48v( 52 actual) battery to the controller of a bldc motor.

The Rawvalue I get at no load connected is 438.
Shouldnt this be close to 512? Also if I use an external power source (5.10v) for the acs I get a no load reading of 650.

In the second case, I also have a AD/DA module connected so i am measuring the current( cannot use serial.print because of DAC and only one serial connection in Arduino Uno) saving it to the eeprom then reading it. ( First dividing by 10 to keep value below 255)

Any ideas would be helpful. Thanks.

The reading is also affected by the reference voltage to UNOs ADC. YOUR readings are as you can expect.

You can add a software serial port with "softwareserial" (there are several solutions to this 'problem')

Arduino ADC is getting reference voltage from the +5V power, so if you connect ACS712 to the same +5V line you 'd minimize an offset error.

If nothing else works, you can do experimentation at different loads and find out what the bias is and account for it in software.