On OBD2 connections, by default RealDash reads the battery voltage using ATRV command. That command returns the battery voltage as the OBD2 adapter see it instead of requesting the voltage from the ECU.
Sometimes the battery voltage reported by ATRV is not calibrated properly showing a wrong value and requires the voltage calibration. To perform voltage calibration:
- Go to the OBD2 connection settings and tap ‘OBD2 Monitor’.
- On top right edit box, Enter command: ATRV to see current battery voltage.
- Use a multimeter to read real battery voltege, preferably from the wire that is feeding the OBD2 adapter.
- For example, multimeter reads 12.45 volts, enter command ATCV 1245 to calibrate the voltage.
Alternatively you can customize the OBD2 connection to replace the ATRV command with an command that reads the voltage from ECU. You can try PID 42, or you may need to use vehicle specific PID. Example to use PID42:
- Download the default OBD2 XML file from https://github.com/janimm/RealDash-extras/blob/master/Channel_description_files/OBD2/realdash_obd2.xml
- replace the line:
<command send="atrv" skipCount="5" targetId="12"></command> <!-- voltage -->
with
<command send="0142" skipCount="5" targetId="12"></command> <!-- voltage -->
Then import the modified XML file to the OBD2 connection settings.