Here's a way to "top off" the supercap so that the real time clock can be maintained for longer, though I have not yet tested how much extra time it buys you. This is useful if you plan on leaving your car idle for more than a week. I am assuming that you have access to the camera buttons.
1) After you park the car, keep the engine running.
2) Manually stop recording on Mobius.
3) Once the file has been saved, turn off Mobius.
4) Wait for a few seconds (may be 10 sec?) and the green "charging" LED will come on.
5) When the supercap is fully charged, the green light will turn off. Should take less than 30 sec.
6) Turn off car.
The theory here is that by saving the file when under power, the charge on the supercap will not be reduced and hence, there will be more left to power the real time clock. Obviously, if you are driving the car often, don't bother with this.