# Charging voltage in freez value with Bluetooth obd2

**URL:** <https://forum.realdash.net/t/charging-voltage-in-freez-value-with-bluetooth-obd2/4538>\
**Category:** General\
**Created:** [January 21, 2024, 8:12pm UTC](https://forum.realdash.net/t/charging-voltage-in-freez-value-with-bluetooth-obd2/4538 "2024-01-21T20:12:42Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Haleem](https://forum.realdash.net/letter_avatar_proxy/v4/letter/h/9f8e36/32.png) [@Haleem](https://forum.realdash.net/u/Haleem)\
**Post date:** [January 21, 2024, 8:12pm UTC](https://forum.realdash.net/t/charging-voltage-in-freez-value-with-bluetooth-obd2/4538/1 "2024-01-21T20:12:42Z")

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Hello  
Need help please  
I have no problem with obd2 wifi in realdash app  
but when I used obd2 Bluetooth the charging voltage 8 volt in freez condition in all realdash files  
Regard

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**Author:** ![realdashdev](https://forum.realdash.net/user_avatar/forum.realdash.net/realdashdev/32/6_2.png) [@realdashdev](https://forum.realdash.net/u/realdashdev)\
**Post date:** [January 22, 2024, 7:30am UTC](https://forum.realdash.net/t/charging-voltage-in-freez-value-with-bluetooth-obd2/4538/2 "2024-01-22T07:30:33Z")

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RealDash uses ATRV command to read the battery voltage on OBD2 connections. A reply to this command is from the OBD2 adapter, the request is never sent to the vehicle.

Unfortunately some adapters are not calibrated correctly for the voltage, so they show completely different value than actual voltage of the vehicle.

Here is some instructions on how to calibrate your adapters voltage reading:

[How to calibrate the OBD2 battery voltage - Connectivity / OBD2 - RealDash Forum](https://forum.realdash.net/t/how-to-calibrate-the-obd2-battery-voltage/644)