I will be doing a lot of camping on my bicycle in the winter and am looking for a way to charge my laptop by a dynamo. My laptop is an ultra efficient Asus model and only uses around 8.5 watts per hour of use. Given that no solution is 100% efficient I gather I will need around 10 watts of power per hour to charge the laptop for each hour of peddling. I know I could charge it over a longer period of time however I want to aim for 1 hour of peddling equating to 1 hour of charge.
Is there anything out that that would suit my needs, or maybe something I could adapt / make? The highest power dynamo I seem to be able to find is the Busch and Muller Dymotec S12. This outputs 12 volts but only at 6watts. If I went for something in the 12 volt range would I be able to use a 12 volt car charger with the laptop to take it up to the 19 volts that the laptop charges at?
Any ideas would be much appreciated