So we watch films on the laptop but the inbuilt battery only lasts about two and half hours so if iv'e been using it theres sometimes not enough power to watch the whole film and have to plug the inverter on, my question is do I run the laptop down first or run it with the laptop from the start, as we usually travell every day I normally charge the laptop with the inverter as were travelling is that the best practice? I have 2 x 100w leisure batteries.