Hello,
Thank you for your question,
If device is configured the I/O parameters are sent in every AVL packet, in the configurator you should find "Battery Level/Battery Current" in I/O parameters tab and select LOW/HIGH/PANIC priority. The AVL packet is sent using CODEC8 protocol, this data must be then parsed at the server side to get the element's information. Please find information of CODECS in the following link:
https://wiki.teltonika.lt/view/Codec
You can also check the status of these parameters using SMS command "readio #", # is the AVL ID.
More information on SMS message structure and commands can be found in this link:
https://wiki.teltonika.lt/view/FMB_SMS/GPRS_Commands
AVL IDs can be found here:
https://wiki.teltonika.lt/view/FMB_AVL_ID
To read battery level make sure that element is enabled in the configuration and send SMS command: SMSLogin SMSPassword readio 67, if no SMSLogin, SMSPassword is used double spaces are required in front of "readio" command in the SMS Text.
Regards.