Portable Power

You can buy the gelcell batteries that the portable power packs use at most battery shops for a bit cheaper. For example Super Cheap sell an 18 Ah gelcell for $50. Also you may be able to get a genuine 12 volt power supply for your laptop, or the Targus step-up power supply may suit. This saves converting to 240v then back to 16 volts (or whatever your laptop runs on).

I dont know about the bushranger but...
Buy yourself a GOOD 65ah or greater Battery and an inverter of say 300 watts. Shouldn't cost much more than $300.00 this will give you all the power you will need.

I have had a Bushranger for a while now. They are very good at what they do, and I have even run my Engel fridge from it for 24 Hours !!! As the power gets down it also sets off an alarm ( which is a musical tune ), so that will surprise you sometime in the middle of the morning. It has a torch built in as well, which is quite good and will last a long time. They are also handy to keep topped up, if you need a jump start so this is also quite good. They do however take quite a while to charge up, so you will need to keep this in mind. You won't need a "Pure SineWave" inverter for the laptop, as the switchmode supply will clean up the power up for you. Cheers, Andrew, Outback Oz.