Several manufacturers make 12 volt adapters that allow you to run/charge your laptop from a 12 volt adapter, Kensington for example. As we live in a 110/240 volt world, all laptops are sold with a transformer that converts 240 volt to somewhere between 12 and 24 volt. For example, an apple laptop typically runs on 18.5 volt/85 watt. No one makes an adapter allowing you to power an apple laptop from 12 volt, but there is a US company that will adapt you adapter to connect to a kensington adapter and run on 12 volt.

In an ideal world, laptops and battery charges - like mobile phones and ipods - would be charged from 12 volt directly, when travelling on a bike/in a car/having a solar powered house etc.

Otherwise you would be using an inverter two step up 12 volt to 240, then step it back down again to say 18.5 volt, it doesn't take a scientist to understand that that's a very inefficient way of powering your laptop, with a lot of loss of energy, and it drains even a good deep cycle battery rather quickly.

We're travelling with 2 kids, one apple laptop, two netbooks, and more battery chargers for cameras and torches then I care to mention.

To get the apple laptop converted to run on 12 volt + another kensington adapter to run at leaste one of the netbooks sets you back more then even a 1000 watt mod sine inverter that will run anything...

I've decided to go with a 1000 watt mod sine inverter, no kensington adapter for now, one battery charger that will charge AAA and AA batteries from 12 volt (phew), ipods/iphones charge on 12 volt, but everything else will have to run off an inefficient, but cheap, modified sine inverter.

The money I save by not choosing an expensive pure sine inverter and/or kensington adapter to run laptops from 12 volt is invested in a 130amp/hour agm deep cycle battery. This shouls run the fridge for 3-4 days before recharging, and hopefully allow 'some' charging of laptops as well... When they run out of juice we'll just have to go and play outside!