External battery, that would be no for any laptop although there are external battery based chargers on the market now. Problem with those however is they dont have enough current to run a high end gaming rig. About the highest rating you will find is 20V at 3A where the G751 brick puts out 19.5V and 9-11amps depending on which brick you have. About the best you can do is use one of these to recharge with the machine off.