Indeed the 6-bit channels can be used for signals where not much sensitivity is needed, like the light sensor or the accelerometer (in many cases).
In the previous version of BITalino the battery level was indeed obtained through channel A6 for the purpose of controlling the low battery LED (in addition to providing a way of monitoring the device battery status on the target applications).
In the Plugged device it was disconnected by default in order to enable users to use A6 as an effective sensor data channel (and prevent concurrent analog inputs on that port).
You can re-connect the battery channel on the BITalino Plugged at any time, by shunting the two pads highlighted in the attached picture, although once you do that you shouldn't connect any additional sensor to that channel.
Note however that in our late-model BITalino (r)evolution, the battery level now has its own independent channel to control of the low battery LED (now channels A1-A6 are all effective sensor inputs).
If you want to have the battery level on BITalino (r)evolution you can either connect the ABAT pin to one of the analog inputs (in which case you need to disconnect the sensor connected to that input) or simply read it by using the newly introduced "status" command described here:http://bitalino.com/datasheets/REVOLUTI ... asheet.pdf
The firmware currently being used on BITalino (r)evolution can be found on the following link, but the pin assignment has changed when compared to the original BITalino, reason for which if you're using an older model you should confirm the MCU pin assignment before flashing your device:https://github.com/BITalinoWorld/firmwa ... revolution
The BITalino Team