Can you take the photo clearly on which ACS758 the sensor is. Each of them has specific sensitivity ACS758: Current Sensor IC with 100 µΩ Current Conductor
I guess yours is 20mV/A so it is 50V/A.
Let’s give it shot.
I mean standard power supply that can display voltage, current. You look at the number to calibrate/tuning BATT_ parameter.
Thanks,
Vu.