I am also wanting to do this with the Explorer board, like the OP, but I am more novice than is seemingly required to understand Jan's description as to how to achieve this. The link (http://support.sodaq.com/sodaq-one/battery) is obviously for the Sodaq One board. Will the provided sketch work the same for monitoring the LIR2450 coin cell battery supplied with the Explorer board; or, if not, how would I need to modify it? Also, would I need to physically build a voltage divider? Sorry - as I said - total noob.
I would like to be able to plant the board remotely and be alerted by Cayenne when the battery level falls below a threshold, thereby allowing me to go and rescue it.