0AlphaOmega:
oh! I thought you were using a seperate supply for the motorsand charge both the netbook's battery and the additional 12V battery (likely lipo) simultaneously.
I'm making something similar ATM (no laptop), but using a solar panel to charge a 12V gel battery. Power requirements should be within daily charge capability, but I will be adding a sun-bathing routine if the bat gets low. I'll put the panel at optimum angle and allow the unit to rotate toward the sun. Bit dark for testing at the moment
So waiting for the spring.
Continuous activity is not necessary as this is an exercise in navigation rather doing any useful work. For that I will probably aim to set up a self serve "fuelling point" as the area available will not allow a high enough current density from a PV panel.
Good luck
Are you using anything like a solar charger shield? Can those use an arbitrary external power source instead of a solar panel to recharge the battery?