The 3v battery is not charged inside the SUP system in anyway. However if you think that the SUP will not be used for a long time there is a command which will disable the real time clock. by this way you will conserve the battery power.
1. Insert the sup and let it boot up.
2. At the command prompt issue the following command,
hw-module rtc-oscillator shutdown
Upon entry you will find a similar message as shown below,
%C6K_PLATFORM-4-RTC_OSCILLATOR: The oscillator in the Real Time Clock
is [chars]. Calendar [chars] be maintained during the powered down state of the