Is there some sort of Portable battery charger for my laptop that doesnt require being plugged in?
Short of carrying a car battery and an inverter on board I am not aware of something that will do this. Different laptops require different voltages, so some external battery pack would have to be custom set up for your brand/type of laptop. Depending on your laptop you can buy larger batteries. You could buy a second battery, charge it and then swap it at a suitable point in the flight. On some flights (generally the long haul ones) some seats have a DC outlet. You can buy an AC/DC charger for your laptop that will plug into the seat and power your laptop. Most flights have only a few seats like this, so make sure that you get put in the right seat to do this.