GtD -

It would be assumed that the inverters available in your area would produce the appropriate "mains voltage" for the area where they're sold. They may, of course, be less easily available in your market than in mine, although Dave indicated no problem finding them.

The "laptop power converters" described by Dave are not commonly available - that I've seen - in the US market. Other kinds of DC/DC converters are fairly common, but they're seldom advertised as being suitable for laptops.

The laptop makers here seem pretty fussy about having people use only their power supply with their computer, and in fairness to this attitude it should be admitted that the usual units that they supply do include quite a lot of heavy duty filtering. They also tend to cost $100 to $200 (US) each.

An auto battery should be a very stable and noise-free source, but the charging systems on most automobiles are, by "electronic" standards, extremely noisy. The alternators commonly used actually produce AC currents internally that frequently run into the hundred (or hundreds) volt range. The "spikes" are sent pretty much direct to the battery, where they're supposed to be swamped by the large capacity of the battery, but aren't always. The automakers tend also to use the minimum amount of copper to get by, so any other things that click on and off can cause a lot of trash on the line.

Using the laptop maker's own AC to DC converter gives some assurance that the laptop gets "clean" power - and even using the AC to DC unit off a rather "dirty mains line," a.k.a inverter output, isn't likely to do any harm to the computer. (And you can blame the laptop maker if his device isn't clean enough.)

I don't have any argument with anyone who knowledgably uses another kind of device, but that puts the burden on the user to assess whether the regulation and stability of the device is suited to the laptop application. The inverter/converter route lets even dummies be safe, and doesn't really cause much in watt-hour losses in practice.

And, as Dave said, it gives you a way to run your printer too, if you've got a large enough inverter.

John