The Read Command refers to "AT?ADCVALUE" which stated in Page 6 in spec sheet.
Regarding to the hardware setting, ADC hardware equipped in the circuit and DK Board is the one developers need to use.
There are 3 input voltage options refer to different user scenes which mostly been used.
1.5V is designated for the application powered in by 1 battery
3.3V is designated for the application powered in by 2 batteries
3.9V is designated for the application powered in by Li-On battery.
The default value of the DK board is set as 3.3V option.
For those applications need to use 1.5V or 3.9V, developers can take off the resistor
equipped in R30, and apply on R27 (for 1.5V) or R33 (for 3.9V) to complete the hardware setting.
Regarding to how to obtain the information of battery status, developers can use the AT Read Command “AT?ADCVALUE” to retrieve the battery status information.
(For more detail of Write, Read, Response command table, please to the spec sheet)
PS. AT Command can only be committed under the modules is "No-Bonded" (not paired). Strongly suggests carrying out the Reset function first and then implement the required command to get the information.